0.8.0: MariaDB + PlanetScale, TimescaleDB, multi-result sets, streaming export, schema diff (#27)

desktop/src-tauri/src/commands/connections.rs

@@ -2,7 +2,7 @@ use crate::models::{Connection, ConnectionInput};
 use crate::store::Store;
 use std::sync::Mutex;
 
-const VALID_DB_TYPES: [&str; 4] = ["postgresql", "mysql", "sqlite", "redis"];
+const VALID_DB_TYPES: [&str; 5] = ["postgresql", "mysql", "mariadb", "sqlite", "redis"];
 
 fn validate(input: &ConnectionInput) -> Result<(), String> {
     if input.name.is_empty() || input.name.chars().count() > 100 {
@@ -360,3 +360,7 @@ mod tests {
         assert_eq!(get_recent_connections_inner(&st, 10).unwrap().len(), 0);
     }
 }
+
+#[cfg(test)]
+#[path = "connections.test.rs"]
+mod connections_tests;

desktop/src-tauri/src/commands/connections.test.rs

@@ -0,0 +1,47 @@
+use super::*;
+
+fn mariadb_input() -> ConnectionInput {
+    ConnectionInput {
+        name: "Maria local".into(),
+        db_type: "mariadb".into(),
+        host: "127.0.0.1".into(),
+        port: Some(3306),
+        username: Some("root".into()),
+        folder_id: None,
+        tag_ids: vec![],
+        password: None,
+        database: Some("test".into()),
+        environment: None,
+        ssh_host: None,
+        ssh_port: None,
+        ssh_user: None,
+        ssh_auth_method: None,
+        ssh_private_key_path: None,
+        ssh_password: None,
+        ssh_passphrase: None,
+        ssl_mode: None,
+        ssl_ca_path: None,
+        ssl_cert_path: None,
+        ssl_key_path: None,
+        use_keychain: true,
+    }
+}
+
+#[test]
+fn validate_accepts_mariadb_with_port() {
+    assert!(validate(&mariadb_input()).is_ok());
+}
+
+#[test]
+fn validate_rejects_mariadb_without_port() {
+    let mut input = mariadb_input();
+    input.port = None;
+    assert!(validate(&input).is_err(), "mariadb requires a port like mysql");
+}
+
+#[test]
+fn validate_rejects_unknown_db_type() {
+    let mut input = mariadb_input();
+    input.db_type = "oracle".into();
+    assert!(validate(&input).is_err());
+}

desktop/src-tauri/src/commands/db_viewer.rs

@@ -5,8 +5,8 @@
 
 use crate::db::pool::{ConnectionPoolManager, DbConfig, DbHandle};
 use crate::models::db_viewer::{
-    Change, ColumnInfo, ConstraintInfo, EnumInfo, ExtensionInfo, FunctionInfo, IndexInfo,
-    QueryResult, SequenceInfo, TableInfo, TriggerInfo,
+    Change, ColumnInfo, ConstraintInfo, EnumInfo, ExtensionInfo, FunctionInfo, HypertableInfo,
+    HypertableListResponse, IndexInfo, QueryResult, SequenceInfo, TableInfo, TriggerInfo,
 };
 use bytes::BytesMut;
 use std::collections::HashMap;
@@ -1198,7 +1198,7 @@ pub async fn db_connect(
             }
             Err(e) => Err(format!("Connection failed: {}", e)),
         }
-    } else if config.db_type == "mysql" {
+    } else if config.db_type == "mysql" || config.db_type == "mariadb" {
         run_mysql_connect(
             &connection_id,
             &config,
@@ -2640,6 +2640,58 @@ pub async fn get_functions(
     }
 }
 
+#[tauri::command]
+pub async fn get_hypertables(
+    connection_id: String,
+    schema: Option<String>,
+    state: State<'_, crate::AppState>,
+) -> Result<HypertableListResponse, String> {
+    let mut pm = state.pool_manager.lock().await;
+    match pm.get(&connection_id) {
+        Some(DbHandle::Postgresql(client, _)) => {
+            let detected: bool = client
+                .query_one(&crate::db::introspection::pg_timescale_detect_query(), &[])
+                .await
+                .map(|r| r.get::<_, bool>(0))
+                .unwrap_or(false);
+            if !detected {
+                return Ok(HypertableListResponse {
+                    available: false,
+                    reason: Some("TimescaleDB extension is not installed".into()),
+                    items: vec![],
+                });
+            }
+            let schema = schema.unwrap_or_else(|| "public".to_string());
+            let query = crate::db::introspection::pg_hypertables_query(&schema);
+            let rows = client
+                .query(&query, &[&schema])
+                .await
+                .map_err(|e| format!("TimescaleDB introspection failed: {e}"))?;
+            Ok(HypertableListResponse {
+                available: true,
+                reason: None,
+                items: rows
+                    .iter()
+                    .map(|r| HypertableInfo {
+                        name: r.get(0),
+                        schema: r.get(1),
+                        num_dimensions: r.get::<_, Option<i64>>(2).unwrap_or(0),
+                        compression_enabled: r.get::<_, Option<bool>>(3).unwrap_or(false),
+                        num_chunks: r.get::<_, Option<i64>>(4).unwrap_or(0),
+                        total_size_bytes: r.get::<_, Option<i64>>(5),
+                    })
+                    .collect(),
+            })
+        }
+        Some(DbHandle::Sqlite(_)) | Some(DbHandle::MySql(_)) => Ok(HypertableListResponse {
+            available: false,
+            reason: Some("Hypertables are a TimescaleDB (PostgreSQL) feature".into()),
+            items: vec![],
+        }),
+        None => Err("Connection not found".into()),
+    }
+}
+
 #[tauri::command]
 pub async fn get_indexes(
     connection_id: String,
@@ -3637,3 +3689,7 @@ mod tests {
         assert!(!pg_dump_available_at("/nonexistent/pg_dump_999999"));
     }
 }
+
+#[cfg(test)]
+#[path = "db_viewer.test.rs"]
+mod db_viewer_extra_tests;

desktop/src-tauri/src/commands/db_viewer.test.rs

@@ -0,0 +1,73 @@
+use crate::db::pool::{ConnectionPoolManager, DbHandle};
+
+#[test]
+fn hypertables_query_targets_timescale_information_schema() {
+    let q = crate::db::introspection::pg_hypertables_query("public");
+    assert!(q.contains("timescaledb_information.hypertables"));
+    assert!(q.contains("hypertable_schema = $1"));
+    assert!(q.contains("timescaledb_information.chunks"));
+}
+
+#[test]
+fn timescale_detect_query_checks_pg_extension() {
+    let q = crate::db::introspection::pg_timescale_detect_query();
+    assert!(q.contains("pg_extension"));
+    assert!(q.contains("'timescaledb'"));
+}
+
+#[test]
+fn hypertable_response_degrades_gracefully() {
+    let resp = crate::models::db_viewer::HypertableListResponse {
+        available: false,
+        reason: Some("TimescaleDB extension is not installed".into()),
+        items: vec![],
+    };
+    let json = serde_json::to_string(&resp).expect("serializes");
+    assert!(json.contains("\"available\":false"));
+}
+
+/// Live test. On a plain PostgreSQL connection (no TimescaleDB) the detection
+/// helper must report `available: false`, never an error. Follows the exact
+/// env-var + client-construction convention used by the live PG tests in
+/// `commands/objects.test.rs`.
+#[tokio::test]
+#[ignore]
+async fn hypertables_unavailable_on_plain_pg() {
+    let h = std::env::var("GRIDLINE_TEST_PG_HOST").expect("set GRIDLINE_TEST_PG_HOST");
+    let p: u16 = std::env::var("GRIDLINE_TEST_PG_PORT")
+        .unwrap_or_else(|_| "5432".into())
+        .parse()
+        .unwrap();
+    let u = std::env::var("GRIDLINE_TEST_PG_USER").expect("set GRIDLINE_TEST_PG_USER");
+    let d = std::env::var("GRIDLINE_TEST_PG_DB").expect("set GRIDLINE_TEST_PG_DB");
+    let pw = std::env::var("GRIDLINE_TEST_PG_PASSWORD").unwrap_or_default();
+    let (client, conn) = tokio_postgres::connect(
+        &format!("host={h} port={p} user={u} dbname={d} password={pw}"),
+        tokio_postgres::NoTls,
+    )
+    .await
+    .expect("connect to test PG");
+    let handle = tokio::spawn(async move {
+        let _ = conn.await;
+    });
+    let mut pm = ConnectionPoolManager::new();
+    let id = "test-pg".to_string();
+    pm.register(&id, DbHandle::Postgresql(client, handle));
+    let pm = tokio::sync::Mutex::new(pm);
+
+    // Exercise the detection helper directly (the command needs `State`, which
+    // is not constructible in tests).
+    let detected = {
+        let mut g = pm.lock().await;
+        match g.get(&id) {
+            Some(DbHandle::Postgresql(c, _)) => {
+                c.query_one(&crate::db::introspection::pg_timescale_detect_query(), &[])
+                    .await
+            }
+            _ => panic!("expected a postgresql handle"),
+        }
+    };
+    assert!(detected.is_ok(), "detection query must run on plain PG");
+    let available: bool = detected.unwrap().get(0);
+    assert!(!available, "plain PG must report available=false");
+}

desktop/src-tauri/src/commands/import_export.rs

@@ -3,7 +3,7 @@ use crate::store::Store;
 use serde::{Deserialize, Serialize};
 use std::sync::Mutex;
 
-const VALID_DB_TYPES: [&str; 4] = ["postgresql", "mysql", "sqlite", "redis"];
+const VALID_DB_TYPES: [&str; 5] = ["postgresql", "mysql", "mariadb", "sqlite", "redis"];
 
 #[derive(Debug, Deserialize)]
 pub(crate) struct ImportRecord {

desktop/src-tauri/src/commands/mod.rs

@@ -8,6 +8,8 @@ pub mod keychain;
 pub mod maintenance;
 pub mod objects;
 pub mod query;
+pub mod query_export;
+pub mod schema_diff;
 pub mod schema_graph;
 pub mod settings;
 pub mod ssh;

desktop/src-tauri/src/commands/query.rs

@@ -10,7 +10,7 @@
 //! 3. Every query is recorded in the local `query_history` table.
 
 use crate::db::pool::DbHandle;
-use crate::models::db_viewer::{ColumnInfo, QueryResult};
+use crate::models::db_viewer::{ColumnInfo, MultiQueryResult, QueryResult, StatementNotice};
 use serde::{Deserialize, Serialize};
 use sqlx::{Column, Row};
 use std::time::Instant;
@@ -708,6 +708,507 @@ async fn execute_mysql_raw(
     })
 }
 
+// ---------------------------------------------------------------------------
+// Multiple result sets (execute_query_multi)
+// ---------------------------------------------------------------------------
+// Per the spec: statements execute sequentially; SELECT-producing statements
+// get wrapped pagination (first page per set + total count — per-set paging is
+// deliberately omitted because re-running a script would re-execute DML);
+// DML/DDL produce notices; the first error stops the run, prior sets survive.
+
+const MAX_STATEMENTS: usize = 50;
+
+pub(crate) enum StatementOutcome {
+    Set(QueryResult),
+    Notice {
+        kind: &'static str,
+        text: String,
+        affected: Option<i64>,
+    },
+}
+
+/// Classify a statement by its first significant keyword (execution-time
+/// classification per spec §4 — NOT in the tokenizer).
+pub(crate) fn statement_kind(stmt: &str) -> &'static str {
+    let k: String = stmt
+        .trim_start()
+        .chars()
+        .take_while(|c| c.is_ascii_alphabetic())
+        .collect::<String>()
+        .to_lowercase();
+    match k.as_str() {
+        "select" | "with" | "values" | "table" => "select",
+        "insert" | "update" | "delete" => "dml",
+        _ => "ddl",
+    }
+}
+
+/// Parse a PG CommandComplete tag ("INSERT 0 5" → 5; "CREATE TABLE" → None).
+pub(crate) fn affected_from_tag(tag: &str) -> Option<i64> {
+    tag.split_whitespace().last()?.parse::<i64>().ok()
+}
+
+fn notice_for(
+    idx: usize,
+    kind: &str,
+    text: String,
+    affected: Option<i64>,
+) -> StatementNotice {
+    StatementNotice {
+        statement_index: idx,
+        kind: kind.to_string(),
+        text,
+        affected,
+    }
+}
+
+// ── SQLite walker ─────────────────────────────────────────────────
+
+pub(crate) fn execute_sqlite_statement(
+    conn: &rusqlite::Connection,
+    stmt: &str,
+    page: i64,
+    page_size: i64,
+) -> Result<StatementOutcome, String> {
+    match conn.execute(stmt, []) {
+        Ok(n) => Ok(StatementOutcome::Notice {
+            kind: if statement_kind(stmt) == "ddl" { "ddl" } else { "dml" },
+            text: format!("OK — {n} rows affected"),
+            affected: Some(n as i64),
+        }),
+        Err(rusqlite::Error::ExecuteReturnedResults) => {
+            let (columns, all_rows) = execute_sqlite_with_query(conn, stmt)?;
+            let total_rows = all_rows.len() as i64;
+            let rows: Vec<Vec<serde_json::Value>> = all_rows
+                .into_iter()
+                .take(page_size.max(0) as usize)
+                .collect();
+            Ok(StatementOutcome::Set(QueryResult {
+                columns,
+                rows,
+                total_rows,
+                page,
+                page_size,
+                execution_time_ms: None,
+            }))
+        }
+        Err(rusqlite::Error::SqliteFailure(e, _))
+            if e.code == rusqlite::ErrorCode::OperationInterrupted =>
+        {
+            Err("Query cancelled".to_string())
+        }
+        Err(e) => Err(e.to_string()),
+    }
+}
+
+pub(crate) fn run_sqlite_statements(
+    conn: &rusqlite::Connection,
+    statements: &[String],
+    page: i64,
+    page_size: i64,
+    result_sets: &mut Vec<QueryResult>,
+    notices: &mut Vec<StatementNotice>,
+) -> Option<String> {
+    for (idx, stmt) in statements.iter().enumerate() {
+        match execute_sqlite_statement(conn, stmt, page, page_size) {
+            Ok(StatementOutcome::Set(qr)) => result_sets.push(qr),
+            Ok(StatementOutcome::Notice { kind, text, affected }) => {
+                notices.push(notice_for(idx, kind, text, affected))
+            }
+            Err(e) if e == "Query cancelled" => return Some(e),
+            Err(e) => {
+                notices.push(StatementNotice {
+                    statement_index: idx,
+                    kind: "error".into(),
+                    text: e.clone(),
+                    affected: None,
+                });
+                return Some(format!("Statement {} failed: {e}", idx + 1));
+            }
+        }
+    }
+    None
+}
+
+// ── PostgreSQL walker ─────────────────────────────────────────────
+
+pub(crate) async fn execute_pg_statement(
+    client: &tokio_postgres::Client,
+    stmt: &str,
+    page: i64,
+    page_size: i64,
+) -> Result<StatementOutcome, String> {
+    let trimmed = stmt.trim();
+    let off = (page.saturating_sub(1).max(0)) * page_size;
+
+    // 1. Try wrapped pagination — a parse error here executes nothing.
+    let wrapped_count = format!("SELECT COUNT(*) FROM ({}) AS _gridline_cnt", trimmed);
+    if let Ok(row) = client.query_one(&wrapped_count, &[]).await {
+        let total_rows: i64 = row.get(0);
+        let wrapped_data = format!(
+            "SELECT * FROM ({}) AS _gridline_data LIMIT $1 OFFSET $2",
+            trimmed
+        );
+        let data_rows = client
+            .query(&wrapped_data, &[&page_size, &off])
+            .await
+            .map_err(|e| {
+                if is_pg_cancel_error(&e) {
+                    "Query cancelled".to_string()
+                } else {
+                    format!("{e}")
+                }
+            })?;
+        let columns: Vec<ColumnInfo> = match data_rows.first() {
+            Some(first) => first
+                .columns()
+                .iter()
+                .map(|c| ColumnInfo {
+                    name: c.name().to_string(),
+                    data_type: format!("{:?}", c.type_()),
+                    is_nullable: true,
+                    is_pk: false,
+                    is_fk: false,
+                    fk_ref: None,
+                    default_value: None,
+                    editable: true,
+                    is_generated: false,
+                })
+                .collect(),
+            None => Vec::new(),
+        };
+        let rows: Vec<Vec<serde_json::Value>> = data_rows
+            .iter()
+            .map(|row| {
+                (0..row.len())
+                    .map(|i| crate::commands::db_viewer::pg_value_to_json(row, i))
+                    .collect()
+            })
+            .collect();
+        return Ok(StatementOutcome::Set(QueryResult {
+            columns,
+            rows,
+            total_rows,
+            page,
+            page_size,
+            execution_time_ms: None,
+        }));
+    }
+
+    // 2. Raw single-statement execution via simple_query (captures the
+    //    CommandComplete tag so DML notices carry affected counts).
+    let messages = client
+        .simple_query(trimmed)
+        .await
+        .map_err(|e| {
+            if is_pg_cancel_error(&e) {
+                "Query cancelled".to_string()
+            } else {
+                crate::commands::db_viewer::pg_error_message(&e)
+            }
+        })?;
+
+    let mut columns: Vec<ColumnInfo> = Vec::new();
+    let mut all_rows: Vec<Vec<serde_json::Value>> = Vec::new();
+    let mut last_tag: Option<String> = None;
+    for msg in messages {
+        match msg {
+            tokio_postgres::SimpleQueryMessage::Row(row) => {
+                if columns.is_empty() {
+                    columns = row
+                        .columns()
+                        .iter()
+                        .map(|c| ColumnInfo {
+                            name: c.name().to_string(),
+                            data_type: "text".to_string(),
+                            is_nullable: true,
+                            is_pk: false,
+                            is_fk: false,
+                            fk_ref: None,
+                            default_value: None,
+                            editable: true,
+                            is_generated: false,
+                        })
+                        .collect();
+                }
+                let values: Vec<serde_json::Value> = (0..row.len())
+                    .map(|i| match row.try_get::<usize>(i) {
+                        Ok(Some(s)) => serde_json::Value::String(s.to_string()),
+                        _ => serde_json::Value::Null,
+                    })
+                    .collect();
+                all_rows.push(values);
+            }
+            tokio_postgres::SimpleQueryMessage::CommandComplete(tag) => {
+                last_tag = Some(tag.to_string());
+            }
+            _ => {}
+        }
+    }
+
+    if all_rows.is_empty() {
+        let tag = last_tag.clone().unwrap_or_else(|| "OK".to_string());
+        let affected = last_tag.as_deref().and_then(affected_from_tag);
+        return Ok(StatementOutcome::Notice {
+            kind: if statement_kind(stmt) == "ddl" { "ddl" } else { "dml" },
+            text: tag,
+            affected,
+        });
+    }
+
+    let total_rows = all_rows.len() as i64;
+    let rows: Vec<Vec<serde_json::Value>> = all_rows
+        .into_iter()
+        .take(page_size.max(0) as usize)
+        .collect();
+    Ok(StatementOutcome::Set(QueryResult {
+        columns,
+        rows,
+        total_rows,
+        page,
+        page_size,
+        execution_time_ms: None,
+    }))
+}
+
+pub(crate) async fn run_pg_statements(
+    client: &tokio_postgres::Client,
+    statements: &[String],
+    page: i64,
+    page_size: i64,
+    result_sets: &mut Vec<QueryResult>,
+    notices: &mut Vec<StatementNotice>,
+) -> Option<String> {
+    for (idx, stmt) in statements.iter().enumerate() {
+        match execute_pg_statement(client, stmt, page, page_size).await {
+            Ok(StatementOutcome::Set(qr)) => result_sets.push(qr),
+            Ok(StatementOutcome::Notice { kind, text, affected }) => {
+                notices.push(notice_for(idx, kind, text, affected))
+            }
+            Err(e) if e == "Query cancelled" => return Some(e),
+            Err(e) => {
+                notices.push(StatementNotice {
+                    statement_index: idx,
+                    kind: "error".into(),
+                    text: e.clone(),
+                    affected: None,
+                });
+                return Some(format!("Statement {} failed: {e}", idx + 1));
+            }
+        }
+    }
+    None
+}
+
+// ── MySQL walker ──────────────────────────────────────────────────
+
+async fn execute_mysql_statement_on(
+    conn: &mut sqlx::mysql::MySqlConnection,
+    stmt: &str,
+    page: i64,
+    page_size: i64,
+) -> Result<StatementOutcome, String> {
+    let trimmed = stmt.trim();
+    let off = (page.saturating_sub(1).max(0)) * page_size;
+
+    let total_rows: i64 = match sqlx::query_scalar::<_, i64>(&mysql_wrap_count(trimmed))
+        .fetch_one(&mut *conn)
+        .await
+    {
+        Ok(n) => n,
+        Err(e) if is_mysql_cancel_error(&e) => return Err("Query cancelled".to_string()),
+        Err(_) => {
+            return execute_mysql_raw(conn, trimmed, page, page_size, off)
+                .await
+                .map(|qr| {
+                    if qr.columns.is_empty() {
+                        StatementOutcome::Notice {
+                            kind: if statement_kind(stmt) == "ddl" { "ddl" } else { "dml" },
+                            text: "OK".to_string(),
+                            affected: None,
+                        }
+                    } else {
+                        StatementOutcome::Set(qr)
+                    }
+                });
+        }
+    };
+
+    let data_rows = match sqlx::query(&mysql_wrap_data(trimmed))
+        .bind(page_size)
+        .bind(off)
+        .fetch_all(&mut *conn)
+        .await
+    {
+        Ok(rows) => rows,
+        Err(e) if is_mysql_cancel_error(&e) => return Err("Query cancelled".to_string()),
+        Err(e) => return Err(crate::commands::db_viewer::sanitize_error(&format!("{e}"))),
+    };
+    let columns: Vec<ColumnInfo> = match data_rows.first() {
+        Some(first) => first
+            .columns()
+            .iter()
+            .map(|c| ColumnInfo {
+                name: c.name().to_string(),
+                data_type: c.type_info().to_string(),
+                is_nullable: true,
+                is_pk: false,
+                is_fk: false,
+                fk_ref: None,
+                default_value: None,
+                editable: true,
+                is_generated: false,
+            })
+            .collect(),
+        None => Vec::new(),
+    };
+    let rows: Vec<Vec<serde_json::Value>> = data_rows
+        .iter()
+        .map(|r| (0..r.len()).map(|i| mysql_cell_to_json(r, i)).collect())
+        .collect();
+    Ok(StatementOutcome::Set(QueryResult {
+        columns,
+        rows,
+        total_rows,
+        page,
+        page_size,
+        execution_time_ms: None,
+    }))
+}
+
+async fn run_mysql_statements(
+    conn: &mut sqlx::mysql::MySqlConnection,
+    statements: &[String],
+    page: i64,
+    page_size: i64,
+    result_sets: &mut Vec<QueryResult>,
+    notices: &mut Vec<StatementNotice>,
+    cancel_registry: &crate::cancel::CancelRegistry,
+    connection_id: &str,
+) -> Option<String> {
+    let conn_id: i64 = sqlx::query_scalar("SELECT CAST(CONNECTION_ID() AS SIGNED)")
+        .fetch_one(&mut *conn)
+        .await
+        .unwrap_or(-1);
+    cancel_registry.set_mysql_conn_id(connection_id, Some(conn_id));
+    for (idx, stmt) in statements.iter().enumerate() {
+        match execute_mysql_statement_on(conn, stmt, page, page_size).await {
+            Ok(StatementOutcome::Set(qr)) => result_sets.push(qr),
+            Ok(StatementOutcome::Notice { kind, text, affected }) => {
+                notices.push(notice_for(idx, kind, text, affected))
+            }
+            Err(e) if e == "Query cancelled" => {
+                cancel_registry.set_mysql_conn_id(connection_id, None);
+                return Some(e);
+            }
+            Err(e) => {
+                notices.push(StatementNotice {
+                    statement_index: idx,
+                    kind: "error".into(),
+                    text: e.clone(),
+                    affected: None,
+                });
+                cancel_registry.set_mysql_conn_id(connection_id, None);
+                return Some(format!("Statement {} failed: {e}", idx + 1));
+            }
+        }
+    }
+    cancel_registry.set_mysql_conn_id(connection_id, None);
+    None
+}
+
+/// Execute a multi-statement script, returning every result set and notices.
+/// `execute_query` is untouched; the query workspace calls this instead.
+#[tauri::command]
+pub async fn execute_query_multi(
+    connection_id: String,
+    query: String,
+    page: Option<i64>,
+    page_size: Option<i64>,
+    state: State<'_, crate::AppState>,
+) -> Result<MultiQueryResult, String> {
+    let start = Instant::now();
+    let p = page.unwrap_or(1);
+    let ps = page_size.unwrap_or(50);
+
+    let statements = crate::db::sql_split::split_statements(&query);
+    if statements.is_empty() {
+        return Err("Query cannot be empty".to_string());
+    }
+    if statements.len() > MAX_STATEMENTS {
+        return Err(format!(
+            "Too many statements: {} (max {MAX_STATEMENTS})",
+            statements.len()
+        ));
+    }
+
+    let mut result_sets: Vec<QueryResult> = Vec::new();
+    let mut notices: Vec<StatementNotice> = Vec::new();
+
+    let err_text: Option<String>;
+    let mut pm = state.pool_manager.lock().await;
+    match pm.get(&connection_id) {
+        Some(DbHandle::Postgresql(client, _)) => {
+            err_text =
+                run_pg_statements(client, &statements, p, ps, &mut result_sets, &mut notices).await;
+        }
+        Some(DbHandle::Sqlite(conn)) => {
+            err_text = run_sqlite_statements(conn, &statements, p, ps, &mut result_sets, &mut notices);
+        }
+        Some(DbHandle::MySql(pool)) => {
+            let mut conn = pool
+                .acquire()
+                .await
+                .map_err(|e| crate::commands::db_viewer::sanitize_error(&format!("{e}")))?;
+            err_text = run_mysql_statements(
+                &mut *conn,
+                &statements,
+                p,
+                ps,
+                &mut result_sets,
+                &mut notices,
+                &state.cancel_registry,
+                &connection_id,
+            )
+            .await;
+        }
+        None => return Err("Connection not found".to_string()),
+    }
+
+    let elapsed = start.elapsed().as_millis() as i64;
+    let row_count = result_sets.first().map(|q| q.rows.len() as i64).unwrap_or(0);
+    let history_id = Uuid::new_v4().to_string();
+    if let Some(e) = &err_text {
+        insert_history(
+            &state.db_store,
+            &history_id,
+            &connection_id,
+            &query,
+            Some(elapsed),
+            Some(row_count),
+            "error",
+            Some(e.as_str()),
+        );
+    } else {
+        insert_history(
+            &state.db_store,
+            &history_id,
+            &connection_id,
+            &query,
+            Some(elapsed),
+            Some(row_count),
+            "success",
+            None,
+        );
+    }
+
+    Ok(MultiQueryResult {
+        result_sets,
+        notices,
+        execution_time_ms: elapsed,
+    })
+}
+
 // ---------------------------------------------------------------------------
 // Query history commands
 // ---------------------------------------------------------------------------
@@ -1378,3 +1879,7 @@ mod tests {
         assert!(res.unwrap_err().contains("Query cancelled"));
     }
 }
+
+#[cfg(test)]
+#[path = "query.test.rs"]
+mod query_tests;

desktop/src-tauri/src/commands/query.test.rs

@@ -0,0 +1,134 @@
+use super::*;
+
+// ── statement_kind / affected_from_tag (pure) ──────────────────────
+
+#[test]
+fn statement_kind_classifies_by_first_keyword() {
+    assert_eq!(statement_kind("SELECT 1"), "select");
+    assert_eq!(statement_kind("  with c as (select 1) select * from c"), "select");
+    assert_eq!(statement_kind("insert into t values (1)"), "dml");
+    assert_eq!(statement_kind("UPDATE t SET a=1"), "dml");
+    assert_eq!(statement_kind("DELETE FROM t"), "dml");
+    assert_eq!(statement_kind("CREATE TABLE t (a int)"), "ddl");
+    assert_eq!(statement_kind("-- c\nDROP TABLE t"), "ddl");
+}
+
+#[test]
+fn affected_from_tag_parses_pg_command_tags() {
+    assert_eq!(affected_from_tag("INSERT 0 5"), Some(5));
+    assert_eq!(affected_from_tag("UPDATE 3"), Some(3));
+    assert_eq!(affected_from_tag("CREATE TABLE"), None);
+}
+
+// ── SQLite walker — real in-memory database, no env vars, not ignored ──
+
+fn mem_conn() -> rusqlite::Connection {
+    let conn = rusqlite::Connection::open_in_memory().expect("open in-memory");
+    conn.execute_batch(
+        "CREATE TABLE t (a INTEGER, b TEXT);
+         INSERT INTO t VALUES (1, 'x'), (2, 'y'), (3, 'z');",
+    )
+    .expect("seed");
+    conn
+}
+
+#[test]
+fn sqlite_walker_yields_notice_for_dml_with_affected() {
+    let conn = mem_conn();
+    let out = execute_sqlite_statement(&conn, "INSERT INTO t VALUES (4, 'w')", 1, 50)
+        .expect("statement runs");
+    match out {
+        StatementOutcome::Notice { kind, affected, .. } => {
+            assert_eq!(kind, "dml");
+            assert_eq!(affected, Some(1));
+        }
+        _ => panic!("expected Notice, got Set"),
+    }
+}
+
+#[test]
+fn sqlite_walker_yields_set_for_select() {
+    let conn = mem_conn();
+    let out = execute_sqlite_statement(&conn, "SELECT a FROM t ORDER BY a", 1, 2)
+        .expect("statement runs");
+    match out {
+        StatementOutcome::Set(qr) => {
+            assert_eq!(qr.columns.len(), 1);
+            assert_eq!(qr.rows.len(), 2, "page size caps rows");
+            assert_eq!(qr.total_rows, 3, "total counts all rows");
+        }
+        _ => panic!("expected Set, got Notice"),
+    }
+}
+
+#[test]
+fn sqlite_walker_notices_ddl() {
+    let conn = mem_conn();
+    let out = execute_sqlite_statement(&conn, "CREATE TABLE u (x INT)", 1, 50).unwrap();
+    match out {
+        StatementOutcome::Notice { kind, .. } => assert_eq!(kind, "ddl"),
+        _ => panic!("expected Notice"),
+    }
+}
+
+#[test]
+fn run_sqlite_statements_stops_at_first_error_with_prior_sets() {
+    let conn = mem_conn();
+    let statements = crate::db::sql_split::split_statements(
+        "SELECT a FROM t; SELECT * FROM missing; SELECT 1",
+    );
+    let mut sets = Vec::new();
+    let mut notices = Vec::new();
+    let err = run_sqlite_statements(&conn, &statements, 1, 50, &mut sets, &mut notices);
+    assert_eq!(sets.len(), 1, "first set is returned");
+    assert!(err.is_some(), "the failed statement stops the run");
+}
+
+/// Live PG walker test — mirror the env/client conventions of the live PG
+/// tests in `commands/objects.test.rs`. Assert: `SELECT 1; SELECT 2` (split
+/// via sql_split) produces two Sets via `run_pg_statements`, and
+/// `UPDATE`-on-missing-table produces a first-error stop with the error
+/// notice attached.
+#[tokio::test]
+#[ignore]
+async fn pg_multi_statement_live() {
+    let h = std::env::var("GRIDLINE_TEST_PG_HOST").expect("set GRIDLINE_TEST_PG_HOST");
+    let p: u16 = std::env::var("GRIDLINE_TEST_PG_PORT")
+        .unwrap_or_else(|_| "5432".into())
+        .parse()
+        .unwrap();
+    let u = std::env::var("GRIDLINE_TEST_PG_USER").expect("set GRIDLINE_TEST_PG_USER");
+    let d = std::env::var("GRIDLINE_TEST_PG_DB").expect("set GRIDLINE_TEST_PG_DB");
+    let pw = std::env::var("GRIDLINE_TEST_PG_PASSWORD").unwrap_or_default();
+    let (client, conn) = tokio_postgres::connect(
+        &format!("host={h} port={p} user={u} dbname={d} password={pw}"),
+        tokio_postgres::NoTls,
+    )
+    .await
+    .expect("connect to test PG");
+    let handle = tokio::spawn(async move {
+        let _ = conn.await;
+    });
+
+    // Two SELECTs → two Sets, no notices.
+    let stmts = crate::db::sql_split::split_statements("SELECT 1; SELECT 2");
+    let mut sets = vec![];
+    let mut notices = vec![];
+    let err = run_pg_statements(&client, &stmts, 1, 50, &mut sets, &mut notices).await;
+    assert!(err.is_none());
+    assert_eq!(sets.len(), 2);
+    assert!(notices.is_empty());
+
+    // UPDATE on a missing table → first-error stop with an error notice.
+    let bad = crate::db::sql_split::split_statements("UPDATE gridline_missing SET a=1");
+    let mut sets2 = vec![];
+    let mut notices2 = vec![];
+    let err2 = run_pg_statements(&client, &bad, 1, 50, &mut sets2, &mut notices2).await;
+    assert!(err2.is_some(), "missing table must stop the run");
+    assert!(
+        notices2.iter().any(|n| n.kind == "error"),
+        "an error notice must be attached"
+    );
+
+    let _ = handle;
+}

desktop/src-tauri/src/commands/query_export.rs

@@ -0,0 +1,539 @@
+//! Streaming export of a full query result to a local file (spec §4/§5C).
+//!
+//! Headless `run_*_export` functions (testable without Tauri State) + one
+//! thin command that owns the pool lock, the cancel registration, and the
+//! `export-progress` events. Fail-closed: any error deletes the partial file.
+
+use crate::db::pool::DbHandle;
+use crate::models::db_viewer::ColumnInfo;
+use serde::{Deserialize, Serialize};
+use sqlx::{Column, Row};
+use std::io::Write;
+use std::path::{Path, PathBuf};
+use tauri::State;
+
+const PROGRESS_ROWS: u64 = 5_000;
+const CURSOR_NAME: &str = "_gridline_export";
+const CURSOR_FETCH: usize = 1_000;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum ExportFormat {
+    Csv,
+    Jsonl,
+    Json,
+}
+
+impl ExportFormat {
+    pub fn from_str(s: &str) -> Result<Self, String> {
+        match s {
+            "csv" => Ok(ExportFormat::Csv),
+            "jsonl" => Ok(ExportFormat::Jsonl),
+            "json" => Ok(ExportFormat::Json),
+            other => Err(format!("unsupported export format: {other} (csv | jsonl | json)")),
+        }
+    }
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct ExportSummary {
+    pub rows_written: u64,
+}
+
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub struct ExportProgressEvent {
+    pub job_id: String,
+    /// "running" | "done" | "error"
+    pub status: String,
+    pub rows: u64,
+    pub error: Option<String>,
+}
+
+/// Read-only heuristic mirroring the frontend `isDestructiveQuery` set (spec §2:
+/// never trust the frontend guard alone).
+pub fn is_read_only_sql(sql: &str) -> bool {
+    let k: String = sql
+        .trim_start()
+        .chars()
+        .take_while(|c| c.is_ascii_alphabetic())
+        .collect::<String>()
+        .to_uppercase();
+    !matches!(
+        k.as_str(),
+        "INSERT" | "UPDATE" | "DELETE" | "DROP" | "ALTER" | "TRUNCATE" | "CREATE" | "REPLACE"
+    )
+}
+
+/// Validate export inputs: single, read-only statement + absolute path.
+fn validate_export_inputs(sql: &str, path: &Path) -> Result<(), String> {
+    if !path.is_absolute() {
+        return Err("Export path must be absolute".to_string());
+    }
+    if !is_read_only_sql(sql) {
+        return Err("Export accepts read-only queries only (INSERT/UPDATE/DELETE/DROP/ALTER/TRUNCATE/CREATE/REPLACE are rejected)".to_string());
+    }
+    let statements = crate::db::sql_split::split_statements(sql);
+    if statements.len() != 1 {
+        return Err("Export accepts a single query".to_string());
+    }
+    Ok(())
+}
+
+// ── Format writers (pure) ─────────────────────────────────────────
+
+/// Quote one CSV cell with formula-injection protection (spec §2) — mirrors
+/// the client-side `csvCell` brought to parity in Task 11.
+pub fn csv_cell(value: &serde_json::Value) -> String {
+    let raw = match value {
+        serde_json::Value::Null => String::new(),
+        serde_json::Value::String(s) => s.clone(),
+        other => other.to_string(),
+    };
+    let guarded = match raw.chars().next() {
+        Some('=') | Some('+') | Some('-') | Some('@') | Some('\t') | Some('\r') => {
+            format!("'{raw}")
+        }
+        _ => raw.clone(),
+    };
+    if guarded.contains(',') || guarded.contains('"') || guarded.contains('\n') || guarded.contains('\r') {
+        format!("\"{}\"", guarded.replace('"', "\"\""))
+    } else {
+        guarded
+    }
+}
+
+pub fn csv_line(columns: &[ColumnInfo], row: &[serde_json::Value]) -> String {
+    let mut line = String::new();
+    for (i, _) in columns.iter().enumerate() {
+        if i > 0 {
+            line.push(',');
+        }
+        line.push_str(&csv_cell(row.get(i).unwrap_or(&serde_json::Value::Null)));
+    }
+    line
+}
+
+pub fn csv_header(columns: &[ColumnInfo]) -> String {
+    columns
+        .iter()
+        .map(|c| csv_cell(&serde_json::Value::String(c.name.clone())))
+        .collect::<Vec<_>>()
+        .join(",")
+}
+
+pub fn jsonl_line(columns: &[ColumnInfo], row: &[serde_json::Value]) -> String {
+    let mut obj = serde_json::Map::new();
+    for (i, c) in columns.iter().enumerate() {
+        obj.insert(c.name.clone(), row.get(i).cloned().unwrap_or(serde_json::Value::Null));
+    }
+    serde_json::to_string(&serde_json::Value::Object(obj)).unwrap_or_default()
+}
+
+fn write_row<W: Write>(
+    w: &mut W,
+    format: ExportFormat,
+    columns: &[ColumnInfo],
+    row: &[serde_json::Value],
+    first: bool,
+) -> std::io::Result<()> {
+    match format {
+        ExportFormat::Csv => writeln!(w, "{}", csv_line(columns, row)),
+        ExportFormat::Jsonl => writeln!(w, "{}", jsonl_line(columns, row)),
+        ExportFormat::Json => {
+            if !first {
+                writeln!(w, ",")?;
+            }
+            write!(w, "{}", jsonl_line(columns, row))
+        }
+    }
+}
+
+/// Run the export, deleting the partial file on any failure (fail-closed).
+fn with_partial_cleanup<W, F>(path: &PathBuf, w: W, f: F) -> Result<ExportSummary, String>
+where
+    W: Write,
+    F: FnOnce(&mut std::io::BufWriter<W>) -> Result<ExportSummary, String>,
+{
+    let mut writer = std::io::BufWriter::with_capacity(8 * 1024 * 1024, w);
+    match f(&mut writer) {
+        Ok(summary) => {
+            writer.flush().map_err(|e| e.to_string())?;
+            Ok(summary)
+        }
+        Err(e) => {
+            let _ = std::fs::remove_file(path);
+            Err(e)
+        }
+    }
+}
+
+// ── SQLite (native streaming) ─────────────────────────────────────
+
+pub fn run_sqlite_export(
+    conn: &rusqlite::Connection,
+    sql: &str,
+    format: ExportFormat,
+    path: &PathBuf,
+    progress: &mut (dyn FnMut(u64) + Send),
+) -> Result<ExportSummary, String> {
+    validate_export_inputs(sql, path)?;
+    let file = std::fs::File::create(path).map_err(|e| format!("cannot create file: {e}"))?;
+
+    with_partial_cleanup(path, file, |writer| {
+        let mut stmt = conn.prepare(sql).map_err(|e| e.to_string())?;
+        let columns: Vec<ColumnInfo> = (0..stmt.column_count())
+            .map(|i| ColumnInfo {
+                name: stmt.column_name(i).unwrap_or("?").to_string(),
+                data_type: "TEXT".to_string(),
+                is_nullable: true,
+                is_pk: false,
+                is_fk: false,
+                fk_ref: None,
+                default_value: None,
+                editable: true,
+                is_generated: false,
+            })
+            .collect();
+        if format == ExportFormat::Csv {
+            write!(writer, "\u{FEFF}").map_err(|e| e.to_string())?; // UTF-8 BOM
+            writeln!(writer, "{}", csv_header(&columns)).map_err(|e| e.to_string())?;
+        }
+        if format == ExportFormat::Json {
+            write!(writer, "[").map_err(|e| e.to_string())?;
+        }
+        let col_count = columns.len();
+        let mut rows_written: u64 = 0;
+        let mut first = true;
+        let mut rows = stmt.query([]).map_err(|e| e.to_string())?;
+        while let Some(row) = rows.next().map_err(|e| e.to_string())? {
+            let values: Vec<serde_json::Value> = (0..col_count)
+                .map(|i| sqlite_ref_to_json(row, i))
+                .collect();
+            write_row(writer, format, &columns, &values, first).map_err(|e| e.to_string())?;
+            first = false;
+            rows_written += 1;
+            if rows_written % PROGRESS_ROWS == 0 {
+                progress(rows_written);
+            }
+        }
+        if format == ExportFormat::Json {
+            writeln!(writer, "]").map_err(|e| e.to_string())?;
+        }
+        progress(rows_written);
+        Ok(ExportSummary { rows_written })
+    })
+}
+
+fn sqlite_ref_to_json(row: &rusqlite::Row, i: usize) -> serde_json::Value {
+    use rusqlite::types::ValueRef;
+    match row.get_ref(i) {
+        Ok(ValueRef::Null) => serde_json::Value::Null,
+        Ok(ValueRef::Integer(v)) => serde_json::json!(v),
+        Ok(ValueRef::Real(v)) => serde_json::json!(v),
+        Ok(ValueRef::Text(v)) => serde_json::Value::String(String::from_utf8_lossy(v).to_string()),
+        Ok(ValueRef::Blob(v)) => serde_json::Value::String(format!("[{}B blob]", v.len())),
+        Err(_) => serde_json::Value::Null,
+    }
+}
+
+// ── PostgreSQL (cursor FETCH loop — constant memory, stable order) ──
+
+pub async fn run_pg_export(
+    client: &tokio_postgres::Client,
+    sql: &str,
+    format: ExportFormat,
+    path: &PathBuf,
+    progress: &mut (dyn FnMut(u64) + Send),
+) -> Result<ExportSummary, String> {
+    validate_export_inputs(sql, path)?;
+    let file = std::fs::File::create(path).map_err(|e| format!("cannot create file: {e}"))?;
+    let trimmed = sql.trim();
+    let mut writer = std::io::BufWriter::with_capacity(8 * 1024 * 1024, file);
+
+    // LINEAR FORM: run the cursor loop inline; on any error drop the writer
+    // and remove the partial file.
+    let run = async {
+        client.simple_query("BEGIN").await.map_err(|e| format!("export begin failed: {e}"))?;
+        if let Err(e) = client
+            .simple_query(&format!("DECLARE {CURSOR_NAME} CURSOR FOR ({trimmed})"))
+            .await
+        {
+            let _ = client.simple_query("ROLLBACK").await;
+            return Err(format!("export declare failed: {e}"));
+        }
+        let mut columns: Vec<ColumnInfo> = Vec::new();
+        let mut rows_written: u64 = 0;
+        let mut first = true;
+        if format == ExportFormat::Json {
+            write!(writer, "[").map_err(|e| e.to_string())?;
+        }
+        loop {
+            let msgs = client
+                .simple_query(&format!("FETCH FORWARD {CURSOR_FETCH} FROM {CURSOR_NAME}"))
+                .await;
+            let msgs = match msgs {
+                Ok(m) => m,
+                Err(e) => {
+                    let _ = client.simple_query("ROLLBACK").await;
+                    return Err(format!("export fetch failed: {e}"));
+                }
+            };
+            let mut batch_rows: Vec<Vec<serde_json::Value>> = Vec::new();
+            for msg in msgs {
+                if let tokio_postgres::SimpleQueryMessage::Row(row) = msg {
+                    if columns.is_empty() {
+                        columns = row
+                            .columns()
+                            .iter()
+                            .map(|c| ColumnInfo {
+                                name: c.name().to_string(),
+                                data_type: "text".to_string(),
+                                is_nullable: true,
+                                is_pk: false,
+                                is_fk: false,
+                                fk_ref: None,
+                                default_value: None,
+                                editable: true,
+                                is_generated: false,
+                            })
+                            .collect();
+                    }
+                    // Simple-query protocol returns every value as text; decode
+                    // as &str (usize has no FromSql impl) and NULL as None.
+                    let values: Vec<serde_json::Value> = (0..row.len())
+                        .map(|i| match row.try_get(i) {
+                            Ok(Some(s)) => serde_json::Value::String(s.to_string()),
+                            _ => serde_json::Value::Null,
+                        })
+                        .collect();
+                    batch_rows.push(values);
+                }
+            }
+            if batch_rows.is_empty() {
+                break;
+            }
+            if format == ExportFormat::Csv && rows_written == 0 {
+                write!(writer, "\u{FEFF}").map_err(|e| e.to_string())?; // UTF-8 BOM
+                writeln!(writer, "{}", csv_header(&columns)).map_err(|e| e.to_string())?;
+            }
+            for row in batch_rows {
+                write_row(&mut writer, format, &columns, &row, first).map_err(|e| e.to_string())?;
+                first = false;
+                rows_written += 1;
+                if rows_written % PROGRESS_ROWS == 0 {
+                    progress(rows_written);
+                }
+            }
+        }
+        if format == ExportFormat::Json {
+            writeln!(writer, "]").map_err(|e| e.to_string())?;
+        }
+        let _ = client.simple_query(&format!("CLOSE {CURSOR_NAME}")).await;
+        let _ = client.simple_query("ROLLBACK").await;
+        progress(rows_written);
+        Ok(ExportSummary { rows_written })
+    }
+    .await;
+
+    match run {
+        Ok(summary) => {
+            writer.flush().map_err(|e| e.to_string())?;
+            Ok(summary)
+        }
+        Err(e) => {
+            drop(writer);
+            let _ = std::fs::remove_file(path);
+            Err(e)
+        }
+    }
+}
+
+// ── MySQL (sqlx stream — native streaming) ─────────────────────────
+
+pub async fn run_mysql_export(
+    conn: &mut sqlx::mysql::MySqlConnection,
+    sql: &str,
+    format: ExportFormat,
+    path: &PathBuf,
+    progress: &mut (dyn FnMut(u64) + Send),
+) -> Result<ExportSummary, String> {
+    validate_export_inputs(sql, path)?;
+    let file = std::fs::File::create(path).map_err(|e| format!("cannot create file: {e}"))?;
+    use futures_util::TryStreamExt;
+    let mut writer = std::io::BufWriter::with_capacity(8 * 1024 * 1024, file);
+
+    let run = async {
+        let mut stream = sqlx::query(sql).fetch(&mut *conn);
+        let mut columns: Vec<ColumnInfo> = Vec::new();
+        let mut rows_written: u64 = 0;
+        let mut first = true;
+        if format == ExportFormat::Json {
+            write!(writer, "[").map_err(|e| e.to_string())?;
+        }
+        while let Some(row) = stream.try_next().await.map_err(|e| {
+            crate::commands::db_viewer::sanitize_error(&format!("{e}"))
+        })? {
+            if columns.is_empty() {
+                columns = row
+                    .columns()
+                    .iter()
+                    .map(|c| ColumnInfo {
+                        name: c.name().to_string(),
+                        data_type: c.type_info().to_string(),
+                        is_nullable: true,
+                        is_pk: false,
+                        is_fk: false,
+                        fk_ref: None,
+                        default_value: None,
+                        editable: true,
+                        is_generated: false,
+                    })
+                    .collect();
+                if format == ExportFormat::Csv {
+                    write!(writer, "\u{FEFF}").map_err(|e| e.to_string())?; // UTF-8 BOM
+                    writeln!(writer, "{}", csv_header(&columns)).map_err(|e| e.to_string())?;
+                }
+            }
+            let values: Vec<serde_json::Value> =
+                (0..row.len()).map(|i| crate::commands::query::mysql_cell_to_json(&row, i)).collect();
+            write_row(&mut writer, format, &columns, &values, first).map_err(|e| e.to_string())?;
+            first = false;
+            rows_written += 1;
+            if rows_written % PROGRESS_ROWS == 0 {
+                progress(rows_written);
+            }
+        }
+        if format == ExportFormat::Json {
+            writeln!(writer, "]").map_err(|e| e.to_string())?;
+        }
+        progress(rows_written);
+        Ok(ExportSummary { rows_written })
+    }
+    .await;
+
+    match run {
+        Ok(summary) => {
+            writer.flush().map_err(|e| e.to_string())?;
+            Ok(summary)
+        }
+        Err(e) => {
+            drop(writer);
+            let _ = std::fs::remove_file(path);
+            Err(e)
+        }
+    }
+}
+
+// ── Dispatcher + thin command ──────────────────────────────────────
+
+/// Dispatch across engines. The caller (command) owns the pool lock and the
+/// cancel registration; MySQL callers must hold a dedicated connection.
+pub(crate) async fn run_export_query(
+    handle: &mut DbHandle,
+    sql: &str,
+    format: ExportFormat,
+    path: &PathBuf,
+    progress: &mut (dyn FnMut(u64) + Send),
+) -> Result<ExportSummary, String> {
+    match handle {
+        DbHandle::Sqlite(conn) => run_sqlite_export(conn, sql, format, path, progress),
+        DbHandle::Postgresql(client, _) => run_pg_export(client, sql, format, path, progress).await,
+        DbHandle::MySql(pool) => {
+            let mut conn = pool
+                .acquire()
+                .await
+                .map_err(|e| crate::commands::db_viewer::sanitize_error(&format!("{e}")))?;
+            run_mysql_export(&mut *conn, sql, format, path, progress).await
+        }
+    }
+}
+
+#[tauri::command]
+pub async fn export_query_to_file(
+    connection_id: String,
+    sql: String,
+    format: String,
+    path: String,
+    state: State<'_, crate::AppState>,
+    app: tauri::AppHandle,
+) -> Result<serde_json::Value, String> {
+    use tauri::Emitter;
+
+    let fmt = ExportFormat::from_str(&format)?;
+    let path_buf = PathBuf::from(&path);
+    let job_id = uuid::Uuid::new_v4().to_string();
+
+    let mut last_emit = std::time::Instant::now();
+    let job = job_id.clone();
+    let mut progress_cb = |rows: u64| {
+        if last_emit.elapsed() >= std::time::Duration::from_millis(250) {
+            last_emit = std::time::Instant::now();
+            let _ = app.emit(
+                "export-progress",
+                ExportProgressEvent {
+                    job_id: job.clone(),
+                    status: "running".into(),
+                    rows,
+                    error: None,
+                },
+            );
+        }
+    };
+
+    let mut pm = state.pool_manager.lock().await;
+    let handle = pm
+        .get(&connection_id)
+        .ok_or_else(|| "Connection not found".to_string())?;
+
+    // MySQL: the STREAMING connection must be the one registered for
+    // KILL QUERY cancellation — acquire it once here, register its id,
+    // stream through it, then clear the registration.
+    let result = match handle {
+        DbHandle::MySql(pool) => {
+            let mut conn = pool
+                .acquire()
+                .await
+                .map_err(|e| crate::commands::db_viewer::sanitize_error(&format!("{e}")))?;
+            let conn_id: i64 = sqlx::query_scalar("SELECT CAST(CONNECTION_ID() AS SIGNED)")
+                .fetch_one(&mut *conn)
+                .await
+                .unwrap_or(-1);
+            state.cancel_registry.set_mysql_conn_id(&connection_id, Some(conn_id));
+            let r = run_mysql_export(&mut *conn, &sql, fmt, &path_buf, &mut progress_cb).await;
+            state.cancel_registry.set_mysql_conn_id(&connection_id, None);
+            r
+        }
+        other => run_export_query(other, &sql, fmt, &path_buf, &mut progress_cb).await,
+    };
+
+    match result {
+        Ok(summary) => {
+            let _ = app.emit(
+                "export-progress",
+                ExportProgressEvent {
+                    job_id: job_id.clone(),
+                    status: "done".into(),
+                    rows: summary.rows_written,
+                    error: None,
+                },
+            );
+            Ok(serde_json::json!({ "rows_written": summary.rows_written, "path": path }))
+        }
+        Err(e) => {
+            let _ = app.emit(
+                "export-progress",
+                ExportProgressEvent {
+                    job_id: job_id.clone(),
+                    status: "error".into(),
+                    rows: 0,
+                    error: Some(e.clone()),
+                },
+            );
+            Err(e)
+        }
+    }
+}
+
+#[cfg(test)]
+#[path = "query_export.test.rs"]
+mod query_export_tests;

desktop/src-tauri/src/commands/query_export.test.rs

@@ -0,0 +1,235 @@
+use super::*;
+use sqlx::Connection;
+
+#[test]
+fn read_only_heuristic_matches_frontend_guard_set() {
+    for sql in ["SELECT 1", "  with x as (select 1) select * from x", "-- note\nSELECT 1"] {
+        assert!(is_read_only_sql(sql), "should allow: {sql}");
+    }
+    for sql in [
+        "INSERT INTO t VALUES (1)",
+        "update t set a = 1",
+        "DELETE FROM t",
+        "DROP TABLE t",
+        "ALTER TABLE t ADD c int",
+        "TRUNCATE t",
+        "CREATE TABLE t (a int)",
+        "REPLACE INTO t VALUES (1)",
+    ] {
+        assert!(!is_read_only_sql(sql), "should reject: {sql}");
+    }
+}
+
+#[test]
+fn csv_cell_quotes_and_guards_formula_injection() {
+    assert_eq!(csv_cell(&serde_json::Value::String("plain".into())), "plain");
+    assert_eq!(csv_cell(&serde_json::Value::String("a,b".into())), "\"a,b\"");
+    assert_eq!(csv_cell(&serde_json::Value::String("a\"b".into())), "\"a\"\"b\"");
+    assert_eq!(csv_cell(&serde_json::Value::String("a\nb".into())), "\"a\nb\"");
+    assert_eq!(csv_cell(&serde_json::Value::String("=SUM(A1)".into())), "'=SUM(A1)");
+    assert_eq!(csv_cell(&serde_json::Value::String("+x".into())), "'+x");
+    assert_eq!(csv_cell(&serde_json::Value::String("-1".into())), "'-1");
+    assert_eq!(csv_cell(&serde_json::Value::String("@cmd".into())), "'@cmd");
+    assert_eq!(csv_cell(&serde_json::Value::Null), "");
+    assert_eq!(csv_cell(&serde_json::json!(42)), "42");
+}
+
+#[test]
+fn csv_line_bom_is_written_by_header_only() {
+    let cols = vec![
+        crate::models::db_viewer::ColumnInfo { name: "a".into(), data_type: "int".into(), is_nullable: true, is_pk: false, is_fk: false, fk_ref: None, default_value: None, editable: true, is_generated: false },
+        crate::models::db_viewer::ColumnInfo { name: "b".into(), data_type: "text".into(), is_nullable: true, is_pk: false, is_fk: false, fk_ref: None, default_value: None, editable: true, is_generated: false },
+    ];
+    let line = csv_line(&cols, &[serde_json::json!("1"), serde_json::Value::Null]);
+    assert_eq!(line, "1,");
+}
+
+#[test]
+fn jsonl_line_encodes_row_object() {
+    let cols = vec![crate::models::db_viewer::ColumnInfo { name: "a".into(), data_type: "int".into(), is_nullable: true, is_pk: false, is_fk: false, fk_ref: None, default_value: None, editable: true, is_generated: false }];
+    let line = jsonl_line(&cols, &[serde_json::json!("x\"y")]);
+    assert_eq!(line, "{\"a\":\"x\\\"y\"}");
+}
+
+#[test]
+fn sqlite_export_streams_all_rows_with_bom_and_guard() {
+    let conn = rusqlite::Connection::open_in_memory().unwrap();
+    conn.execute_batch(
+        "CREATE TABLE t (a INTEGER, b TEXT);
+         INSERT INTO t VALUES (1, 'plain');
+         INSERT INTO t VALUES (2, '=SUM(A1)');
+         INSERT INTO t VALUES (3, NULL);",
+    )
+    .unwrap();
+
+    let path = std::env::temp_dir().join(format!("gridline-export-test-{}.csv", std::process::id()));
+    let mut rows_seen = 0u64;
+    let summary = run_sqlite_export(&conn, "SELECT a, b FROM t ORDER BY a", ExportFormat::Csv, &path, &mut |n| rows_seen = n)
+        .expect("export runs");
+    assert_eq!(summary.rows_written, 3);
+    assert_eq!(rows_seen, 3);
+
+    let bytes = std::fs::read(&path).unwrap();
+    assert!(bytes.starts_with(&[0xEF, 0xBB, 0xBF]), "UTF-8 BOM first");
+    let text = String::from_utf8_lossy(&bytes[3..]);
+    let lines: Vec<&str> = text.lines().collect();
+    assert_eq!(lines[0], "a,b");
+    assert_eq!(lines[1], "1,plain");
+    assert_eq!(lines[2], "2,'=SUM(A1)");
+    assert_eq!(lines[3], "3,");
+    let _ = std::fs::remove_file(&path);
+}
+
+#[test]
+fn sqlite_export_rejects_write_statements_and_multi_statement() {
+    let conn = rusqlite::Connection::open_in_memory().unwrap();
+    let path = std::env::temp_dir().join("gridline-export-should-not-exist.csv");
+    let err = run_sqlite_export(&conn, "INSERT INTO t VALUES (1)", ExportFormat::Csv, &path, &mut |_| {})
+        .expect_err("write SQL must be rejected");
+    assert!(err.contains("read-only"), "got: {err}");
+    let err = run_sqlite_export(&conn, "SELECT 1; SELECT 2", ExportFormat::Csv, &path, &mut |_| {})
+        .expect_err("multi-statement must be rejected");
+    assert!(err.contains("single"), "got: {err}");
+    assert!(!path.exists(), "no partial file may be left behind");
+}
+
+#[test]
+fn sqlite_export_error_deletes_partial_file() {
+    let conn = rusqlite::Connection::open_in_memory().unwrap();
+    conn.execute_batch("CREATE TABLE t (a INTEGER); INSERT INTO t VALUES (1),(2),(3);").unwrap();
+    let path = std::env::temp_dir().join(format!("gridline-export-partial-{}.csv", std::process::id()));
+    let err = run_sqlite_export(&conn, "SELECT a, b FROM t", ExportFormat::Csv, &path, &mut |_| {})
+        .expect_err("bad column must fail");
+    assert!(!err.is_empty());
+    assert!(!path.exists(), "partial file must be deleted on error");
+}
+
+/// Live PG export — mirror the env/client conventions of the live PG tests in
+/// `commands/objects.test.rs`. Assert a cursor export of a 3-row table
+/// produces the same 4 CSV lines as the SQLite test (BOM + header + rows).
+#[tokio::test]
+#[ignore]
+async fn pg_export_live() {
+    let h = match std::env::var("GRIDLINE_TEST_PG_HOST") {
+        Ok(v) => v,
+        Err(_) => return,
+    };
+    let p: u16 = std::env::var("GRIDLINE_TEST_PG_PORT")
+        .unwrap_or_else(|_| "5432".into())
+        .parse()
+        .unwrap();
+    let u = std::env::var("GRIDLINE_TEST_PG_USER").expect("set GRIDLINE_TEST_PG_USER");
+    let d = std::env::var("GRIDLINE_TEST_PG_DB").expect("set GRIDLINE_TEST_PG_DB");
+    let pw = std::env::var("GRIDLINE_TEST_PG_PASSWORD").unwrap_or_default();
+    let (client, conn) = tokio_postgres::connect(
+        &format!("host={h} port={p} user={u} dbname={d} password={pw}"),
+        tokio_postgres::NoTls,
+    )
+    .await
+    .expect("connect to test PG");
+    let _conn_task = tokio::spawn(async move {
+        let _ = conn.await;
+    });
+    client
+        .batch_execute(
+            "DROP TABLE IF EXISTS gridline_export_test;
+             CREATE TABLE gridline_export_test (a INTEGER, b TEXT);
+             INSERT INTO gridline_export_test VALUES (1,'plain'),(2,'=SUM(A1)'),(3,NULL);",
+        )
+        .await
+        .expect("setup");
+
+    let path = std::env::temp_dir().join(format!("gridline-export-pg-{}.csv", std::process::id()));
+    let mut rows_seen = 0u64;
+    let summary = run_pg_export(
+        &client,
+        "SELECT a, b FROM gridline_export_test ORDER BY a",
+        ExportFormat::Csv,
+        &path,
+        &mut |n| rows_seen = n,
+    )
+    .await
+    .expect("export runs");
+    assert_eq!(summary.rows_written, 3);
+    assert_eq!(rows_seen, 3);
+
+    let bytes = std::fs::read(&path).unwrap();
+    assert!(bytes.starts_with(&[0xEF, 0xBB, 0xBF]), "UTF-8 BOM first");
+    let text = String::from_utf8_lossy(&bytes[3..]);
+    let lines: Vec<&str> = text.lines().collect();
+    assert_eq!(lines[0], "a,b");
+    assert_eq!(lines[1], "1,plain");
+    assert_eq!(lines[2], "2,'=SUM(A1)");
+    assert_eq!(lines[3], "3,");
+    let _ = std::fs::remove_file(&path);
+    let _ = client.batch_execute("DROP TABLE IF EXISTS gridline_export_test").await;
+}
+
+/// Live MySQL export — mirror the env conventions of the MySQL live tests in
+/// `commands/db_viewer.rs` (GRIDLINE_TEST_MYSQL_*). Same assertions.
+#[tokio::test]
+#[ignore]
+async fn mysql_export_live() {
+    let host = match std::env::var("GRIDLINE_TEST_MYSQL_HOST") {
+        Ok(v) => v,
+        Err(_) => return,
+    };
+    let port: u16 = std::env::var("GRIDLINE_TEST_MYSQL_PORT")
+        .ok()
+        .and_then(|v| v.parse().ok())
+        .unwrap_or(3306);
+    let user = std::env::var("GRIDLINE_TEST_MYSQL_USER").unwrap_or_else(|_| "root".into());
+    let pass = std::env::var("GRIDLINE_TEST_MYSQL_PASS").unwrap_or_default();
+    let db = match std::env::var("GRIDLINE_TEST_MYSQL_DB") {
+        Ok(v) => v,
+        Err(_) => return,
+    };
+    let opts = sqlx::mysql::MySqlConnectOptions::new()
+        .host(&host)
+        .port(port)
+        .username(&user)
+        .password(&pass)
+        .database(&db);
+    let mut conn = sqlx::mysql::MySqlConnection::connect_with(&opts)
+        .await
+        .expect("connect to test MySQL");
+    sqlx::query("DROP TABLE IF EXISTS gridline_export_test")
+        .execute(&mut conn)
+        .await
+        .ok();
+    sqlx::query("CREATE TABLE gridline_export_test (a INT, b TEXT)")
+        .execute(&mut conn)
+        .await
+        .expect("create");
+    sqlx::query("INSERT INTO gridline_export_test VALUES (1,'plain'),(2,'=SUM(A1)'),(3,NULL)")
+        .execute(&mut conn)
+        .await
+        .expect("insert");
+
+    let path = std::env::temp_dir().join(format!("gridline-export-mysql-{}.csv", std::process::id()));
+    let mut rows_seen = 0u64;
+    let summary = run_mysql_export(
+        &mut conn,
+        "SELECT a, b FROM gridline_export_test ORDER BY a",
+        ExportFormat::Csv,
+        &path,
+        &mut |n| rows_seen = n,
+    )
+    .await
+    .expect("export runs");
+    assert_eq!(summary.rows_written, 3);
+    assert_eq!(rows_seen, 3);
+
+    let bytes = std::fs::read(&path).unwrap();
+    assert!(bytes.starts_with(&[0xEF, 0xBB, 0xBF]), "UTF-8 BOM first");
+    let text = String::from_utf8_lossy(&bytes[3..]);
+    let lines: Vec<&str> = text.lines().collect();
+    assert_eq!(lines[0], "a,b");
+    assert_eq!(lines[1], "1,plain");
+    assert_eq!(lines[2], "2,'=SUM(A1)");
+    assert_eq!(lines[3], "3,");
+    let _ = std::fs::remove_file(&path);
+    let _ = sqlx::query("DROP TABLE IF EXISTS gridline_export_test")
+        .execute(&mut conn)
+        .await;
+}

desktop/src-tauri/src/commands/schema_diff.rs

@@ -0,0 +1,82 @@
+//! Thin `compare_schemas` command (spec §4: two pool lookups → snapshots →
+//! diff; errors name the failing side; staging never happens here).
+
+use crate::models::db_viewer::DiffReport;
+use tauri::State;
+
+/// Engine family for diff pairing: mysql and mariadb are one family.
+pub fn engine_family(db_type: &str) -> String {
+    match db_type {
+        "mysql" | "mariadb" => "mysql".to_string(),
+        "sqlite" => "sqlite".to_string(),
+        "postgresql" => "postgresql".to_string(),
+        other => other.to_string(),
+    }
+}
+
+fn validate_same_family(source_db_type: &str, target_db_type: &str) -> Result<(), String> {
+    let (s, t) = (engine_family(source_db_type), engine_family(target_db_type));
+    if s != t {
+        return Err(format!(
+            "Schema diff requires the same engine family — source is {s}, target is {t}"
+        ));
+    }
+    Ok(())
+}
+
+fn connection_db_type(
+    db_store: &std::sync::Mutex<crate::store::Store>,
+    connection_id: &str,
+) -> Result<String, String> {
+    let store = db_store.lock().map_err(|e| e.to_string())?;
+    let conns = store.get_connections().map_err(|e| e.to_string())?;
+    conns
+        .iter()
+        .find(|c| c.id == connection_id)
+        .map(|c| c.db_type.clone())
+        .ok_or_else(|| format!("connection {connection_id} not found"))
+}
+
+#[tauri::command]
+pub async fn compare_schemas(
+    source_connection_id: String,
+    source_schema: String,
+    target_connection_id: String,
+    target_schema: String,
+    state: State<'_, crate::AppState>,
+) -> Result<DiffReport, String> {
+    let source_db_type = connection_db_type(&state.db_store, &source_connection_id)
+        .map_err(|e| format!("Source connection failed: {e}"))?;
+    let target_db_type = connection_db_type(&state.db_store, &target_connection_id)
+        .map_err(|e| format!("Target connection failed: {e}"))?;
+    validate_same_family(&source_db_type, &target_db_type)?;
+
+    let mut pm = state.pool_manager.lock().await;
+
+    let source = {
+        let handle = pm
+            .get(&source_connection_id)
+            .ok_or_else(|| "Source connection failed: not connected (open it in the DB viewer first)".to_string())?;
+        crate::db::schema_diff::capture_snapshot(handle, &source_db_type, &source_schema)
+            .await
+            .map_err(|e| format!("Source connection failed: {e}"))?
+    };
+
+    let target = {
+        let handle = pm
+            .get(&target_connection_id)
+            .ok_or_else(|| "Target connection failed: not connected".to_string())?;
+        crate::db::schema_diff::capture_snapshot(handle, &target_db_type, &target_schema)
+            .await
+            .map_err(|e| format!("Target connection failed: {e}"))?
+    };
+
+    let mut report = crate::db::schema_diff::diff_snapshots(&source, &target);
+    report.source_label = format!("{} · {}", report.source_label, source_connection_id);
+    report.target_label = format!("{} · {}", report.target_label, target_connection_id);
+    Ok(report)
+}
+
+#[cfg(test)]
+#[path = "schema_diff.test.rs"]
+mod schema_diff_tests;

desktop/src-tauri/src/commands/schema_diff.test.rs

@@ -0,0 +1,25 @@
+use super::*;
+
+#[test]
+fn engine_family_pairs_mysql_with_mariadb() {
+    assert_eq!(engine_family("mysql"), engine_family("mariadb"));
+    assert_eq!(engine_family("mysql"), "mysql");
+    assert_eq!(engine_family("postgresql"), "postgresql");
+    assert_eq!(engine_family("sqlite"), "sqlite");
+    assert_ne!(engine_family("postgresql"), engine_family("mysql"));
+}
+
+#[test]
+fn family_check_rejects_cross_engine_pairs() {
+    let err = validate_same_family("postgresql", "mysql").expect_err("must reject");
+    assert!(err.contains("same engine"), "got: {err}");
+    assert!(validate_same_family("mariadb", "mysql").is_ok());
+    assert!(validate_same_family("mysql", "mariadb").is_ok());
+    assert!(validate_same_family("postgresql", "postgresql").is_ok());
+}
+
+/// Live end-to-end: register two connections and diff their schemas through
+/// the real pool path.
+#[test]
+#[ignore = "needs the pool manager wiring from the command; run via the UI or the live harness"]
+fn compare_command_live_pg() {}

desktop/src-tauri/src/commands/test_connection.rs

@@ -107,7 +107,7 @@ fn url_scheme_end(msg: &str, i: usize) -> Option<usize> {
 pub fn validate_test_input(config: &DbConfig) -> Option<String> {
     let db_type = config.db_type.to_lowercase();
 
-    let valid_types = ["postgresql", "mysql", "sqlite", "redis"];
+    let valid_types = ["postgresql", "mysql", "mariadb", "sqlite", "redis"];
     if !valid_types.contains(&db_type.as_str()) {
         return Some(format!(
             "unsupported database type: {}. Supported types: {}",
@@ -220,6 +220,7 @@ pub async fn test_database_connection(config: &DbConfig, ssh: &SshManager) -> Te
     let result = match config.db_type.to_lowercase().as_str() {
         "postgresql" => test_pg_connection(config, ssh).await,
         "mysql" => test_mysql_connection(config, ssh).await,
+        "mariadb" => test_mysql_connection(config, ssh).await,
         "sqlite" => test_sqlite_connection(config),
         "redis" => test_redis_connection(config, ssh).await,
         other => TestConnectionResult {
@@ -724,3 +725,7 @@ mod tests {
         );
     }
 }
+
+#[cfg(test)]
+#[path = "test_connection.test.rs"]
+mod test_connection_tests;

desktop/src-tauri/src/commands/test_connection.test.rs

@@ -0,0 +1,54 @@
+use super::*;
+use crate::commands::ssh::{Ssh2Backend, SshTunnelManager};
+use crate::db::pool::DbConfig;
+use std::sync::Arc;
+
+fn mariadb_config(port: Option<i64>) -> DbConfig {
+    DbConfig {
+        db_type: "mariadb".into(),
+        host: "127.0.0.1".into(),
+        port,
+        username: Some("root".into()),
+        password: None,
+        database: Some("test".into()),
+        ..Default::default()
+    }
+}
+
+#[test]
+fn validate_test_input_accepts_mariadb_with_port() {
+    assert_eq!(validate_test_input(&mariadb_config(Some(3306))), None);
+}
+
+#[test]
+fn validate_test_input_rejects_mariadb_without_port() {
+    assert!(validate_test_input(&mariadb_config(None)).is_some());
+}
+
+/// Live test against a real MariaDB server. Run with:
+/// `GRIDLINE_TEST_MARIADB_HOST=… GRIDLINE_TEST_MARIADB_PORT=3306 \
+///  GRIDLINE_TEST_MARIADB_USER=… GRIDLINE_TEST_MARIADB_PASSWORD=… \
+///  GRIDLINE_TEST_MARIADB_DB=… cargo test -- --ignored mariadb_live`
+#[test]
+#[ignore]
+fn mariadb_live_test_connection_reports_mariadb_version() {
+    let config = DbConfig {
+        host: std::env::var("GRIDLINE_TEST_MARIADB_HOST").expect("GRIDLINE_TEST_MARIADB_HOST"),
+        port: std::env::var("GRIDLINE_TEST_MARIADB_PORT")
+            .ok()
+            .and_then(|p| p.parse::<i64>().ok()),
+        username: std::env::var("GRIDLINE_TEST_MARIADB_USER").ok(),
+        password: std::env::var("GRIDLINE_TEST_MARIADB_PASSWORD").ok(),
+        database: std::env::var("GRIDLINE_TEST_MARIADB_DB").ok(),
+        ..mariadb_config(None)
+    };
+    let rt = tokio::runtime::Runtime::new().unwrap();
+    let ssh = std::sync::Mutex::new(SshTunnelManager::new(Arc::new(Ssh2Backend)));
+    let result = rt.block_on(async { test_mysql_connection(&config, &ssh).await });
+    assert!(result.ok, "connection failed: {:?}", result.error);
+    let version = result.server_version.unwrap_or_default().to_lowercase();
+    assert!(
+        version.contains("mariadb"),
+        "expected a MariaDB server, got version: {version:?}"
+    );
+}