refactor(postgres): replace sqlx with tokio-postgres + deadpool-postgres

- Use client.transaction() for safer transaction handling
- Add prepare_cached for all system queries to enable statement caching
- Use query_raw streaming to avoid buffering large result sets
- Add batch_execute support for bulk DDL scripts
- Add COPY protocol support (copy_in / copy_out) for fast data transfer
- Add pg_quote_ident to prevent SQL injection in SET search_path
- Increase connection pool max_size from 5 to 10
- Fix list_indexes bounds check for expression indexes

crates/dbx-core/Cargo.toml

@@ -16,10 +16,13 @@ log = "0.4"
 tokio = { version = "1", features = ["full"] }
 tokio-util = { version = "0.7", features = ["compat"] }
 chrono = { version = "0.4", features = ["serde"] }
-rust_decimal = { version = "1", features = ["serde"] }
+rust_decimal = { version = "1", features = ["serde", "db-postgres"] }
 anyhow = "1"
 uuid = { version = "1", features = ["v4", "serde"] }
-sqlx = { version = "0.8", features = ["runtime-tokio", "tls-rustls", "postgres", "json", "chrono", "uuid", "rust_decimal"] }
+tokio-postgres = { version = "0.7", features = ["with-chrono-0_4", "with-uuid-1", "with-serde_json-1"] }
+deadpool-postgres = { version = "0.14", features = ["rt_tokio_1"] }
+tokio-postgres-rustls = "0.13"
+webpki-roots = "0.26"
 rusqlite = { version = "0.32", features = ["bundled"] }
 mysql_async = { version = "0.36", default-features = false, features = ["default-rustls", "client_ed25519", "chrono", "rust_decimal"] }
 sqlparser = "0.62.0"
@@ -37,4 +40,5 @@ csv = "1"
 calamine = "0.30.1"
 base64 = "0.22"
 async-trait = "0.1"
+bytes = "1"
 zip = { version = "2", default-features = false, features = ["deflate"] }

crates/dbx-core/src/connection.rs

@@ -41,7 +41,7 @@ pub enum MysqlMode {
 
 pub enum PoolKind {
     Mysql(db::mysql::MySqlPool, MysqlMode),
-    Postgres(sqlx::postgres::PgPool),
+    Postgres(deadpool_postgres::Pool),
     Sqlite(db::sqlite::SqliteHandle),
     Redis(tokio::sync::Mutex<redis::aio::MultiplexedConnection>),
     DuckDb(Arc<std::sync::Mutex<duckdb::Connection>>),

crates/dbx-core/src/query.rs

@@ -916,7 +916,7 @@ pub async fn execute_statements_in_transaction(
 
 /// Owned pool variants for safe dispatch across async boundaries.
 enum TxPath {
-    Pg(sqlx::postgres::PgPool),
+    Pg(deadpool_postgres::Pool),
     Mysql(mysql_async::Pool, bool),
     Sqlite(db::sqlite::SqliteHandle),
     Explicit,
@@ -925,32 +925,32 @@ enum TxPath {
 
 // Each of these acquires a dedicated connection and runs all statements within
 // BEGIN ... COMMIT/ROLLBACK, guaranteeing a single physical connection.
-// This avoids sqlx::Transaction<T> which has Send/lifetime incompatibility with Tauri macro.
 
 async fn exec_tx_pg_inner(
-    pool: sqlx::postgres::PgPool,
+    pool: deadpool_postgres::Pool,
     statements: &[String],
     schema: Option<&str>,
     start: std::time::Instant,
 ) -> Result<db::QueryResult, String> {
-    let mut conn = pool.acquire().await.map_err(|e| format!("Failed to acquire connection: {}", e))?;
-    // Set schema first
+    let mut client = pool.get().await.map_err(|e| format!("Failed to acquire connection: {}", e))?;
     if let Some(s) = schema {
-        let sp = format!("SET search_path TO \"{}\", public", s);
-        sqlx::query(&sp).execute(&mut *conn).await.map_err(|e| format!("SET search_path failed: {}", e))?;
+        client
+            .execute(&format!("SET search_path TO {}, public", db::postgres::pg_quote_ident(s)), &[])
+            .await
+            .map_err(|e| format!("SET search_path failed: {}", e))?;
     }
-    sqlx::query("BEGIN").execute(&mut *conn).await.map_err(|e| format!("Failed to begin transaction: {}", e))?;
+    let tx = client.transaction().await.map_err(|e| format!("Failed to begin transaction: {}", e))?;
     let mut total_affected: u64 = 0;
     for (i, sql) in statements.iter().enumerate() {
-        match sqlx::query(sql).execute(&mut *conn).await {
-            Ok(r) => total_affected += r.rows_affected(),
+        match tx.execute(sql, &[]).await {
+            Ok(affected) => total_affected += affected,
             Err(e) => {
-                let _ = sqlx::query("ROLLBACK").execute(&mut *conn).await;
+                // Transaction auto-rollbacks on drop
                 return Err(format!("Statement {} failed: {}", i + 1, e));
             }
         }
     }
-    sqlx::query("COMMIT").execute(&mut *conn).await.map_err(|e| format!("COMMIT failed: {}", e))?;
+    tx.commit().await.map_err(|e| format!("COMMIT failed: {}", e))?;
     Ok(db::QueryResult {
         columns: vec![],
         rows: vec![],

crates/dbx-core/src/schema.rs

@@ -1118,7 +1118,7 @@ pub async fn sqlite_ddl(pool: &db::sqlite::SqliteHandle, table: &str) -> Result<
     .map_err(|e| e.to_string())?
 }
 
-pub async fn pg_ddl(pool: &sqlx::postgres::PgPool, schema: &str, table: &str) -> Result<String, String> {
+pub async fn pg_ddl(pool: &deadpool_postgres::Pool, schema: &str, table: &str) -> Result<String, String> {
     let (columns, indexes, fkeys) = tokio::try_join!(
         db::postgres::get_columns(pool, schema, table),
         db::postgres::list_indexes(pool, schema, table),