From 4e07f731579500251dd0d201d3fe8103bb8e22a9 Mon Sep 17 00:00:00 2001
From: hb <34821912+chenhbb@users.noreply.github.com>
Date: Mon, 22 Jun 2026 00:37:41 +0800
Subject: [PATCH] fix(mysql): preserve temporary tables in client session pools

Disable COM_RESET_CONNECTION for single-connection session pools
(max_connections == 1) so that MySQL session state such as TEMPORARY
TABLEs is not cleared when a connection is returned to the pool.

Closes #1509
---
 crates/dbx-core/src/db/mysql.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/crates/dbx-core/src/db/mysql.rs b/crates/dbx-core/src/db/mysql.rs
index 8ce4b5ddc..c5ffc2d7f 100644
--- a/crates/dbx-core/src/db/mysql.rs
+++ b/crates/dbx-core/src/db/mysql.rs
@@ -417,9 +417,13 @@ fn create_pool(url: &str, ca_cert_path: Option<&str>, max_connections: usize) ->
         mysql_async::Opts::from_url(&mysql_async_url(&tls_url.url)).map_err(|e| format!("Invalid MySQL URL: {e}"))?;
     let base_ssl_opts = opts.ssl_opts().cloned();
     let max_connections = max_connections.max(1);
+    // Single-connection pools (max_connections == 1) are client session pools that
+    // must preserve session state (e.g. TEMPORARY TABLEs) across queries.
+    // Disable COM_RESET_CONNECTION for these pools to avoid clearing that state.
     let pool_opts = mysql_async::PoolOpts::new()
         .with_constraints(mysql_async::PoolConstraints::new(1, max_connections).unwrap())
-        .with_inactive_connection_ttl(Duration::from_secs(300));
+        .with_inactive_connection_ttl(Duration::from_secs(300))
+        .with_reset_connection(max_connections > 1);
     let mut builder = mysql_async::OptsBuilder::from_opts(opts)
         .stmt_cache_size(0)
         .prefer_socket(false)