From 54e61a5c44333f26f8cc822ac47e50f6130044bc Mon Sep 17 00:00:00 2001
From: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
Date: Wed, 20 Apr 2022 07:39:27 +0300
Subject: [PATCH] OnlineDDL: skip GetSchema where possible (#10107)

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
---
 go/vt/schemamanager/tablet_executor.go | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/go/vt/schemamanager/tablet_executor.go b/go/vt/schemamanager/tablet_executor.go
index 995b3f8cafe..4857f592fb1 100644
--- a/go/vt/schemamanager/tablet_executor.go
+++ b/go/vt/schemamanager/tablet_executor.go
@@ -217,6 +217,17 @@ func (exec *TabletExecutor) isOnlineSchemaDDL(stmt sqlparser.Statement) (isOnlin
 //   1. Alter more than 100,000 rows.
 //   2. Change a table with more than 2,000,000 rows (Drops are fine).
 func (exec *TabletExecutor) detectBigSchemaChanges(ctx context.Context, parsedDDLs []sqlparser.DDLStatement) (bool, error) {
+	// We want to avoid any overhead if possible. If all DDLs are online schema changes, then we want to
+	// skip GetSchema altogether.
+	foundAnyNonOnlineDDL := false
+	for _, ddl := range parsedDDLs {
+		if !exec.isOnlineSchemaDDL(ddl) {
+			foundAnyNonOnlineDDL = true
+		}
+	}
+	if !foundAnyNonOnlineDDL {
+		return false, nil
+	}
 	// exec.tablets is guaranteed to have at least one element;
 	// Otherwise, Open should fail and executor should fail.
 	primaryTabletInfo := exec.tablets[0]