feat: add TableExists method for mysql dialect (#895)

CHANGELOG.md

@@ -7,6 +7,8 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+- Add `TableExists` table existence check for the mysql dialect (#895)
+
 ## [v3.24.1]
 
 - Fix regression (`v3.23.1` and `v3.24.0`) in postgres migration table existence check for

internal/dialect/dialectquery/dialectquery.go

@@ -1,5 +1,7 @@
 package dialectquery
 
+import "strings"
+
 // Querier is the interface that wraps the basic methods to create a dialect specific query.
 type Querier interface {
 	// CreateTable returns the SQL query string to create the db version table.
@@ -47,3 +49,11 @@ func (c *QueryController) TableExists(tableName string) string {
 	}
 	return ""
 }
+
+func parseTableIdentifier(name string) (schema, table string) {
+	schema, table, found := strings.Cut(name, ".")
+	if !found {
+		return "", name
+	}
+	return schema, table
+}

internal/dialect/dialectquery/mysql.go

@@ -41,3 +41,13 @@ func (m *Mysql) GetLatestVersion(tableName string) string {
 	q := `SELECT MAX(version_id) FROM %s`
 	return fmt.Sprintf(q, tableName)
 }
+
+func (m *Mysql) TableExists(tableName string) string {
+	schemaName, tableName := parseTableIdentifier(tableName)
+	if schemaName != "" {
+		q := `SELECT EXISTS ( SELECT 1 FROM information_schema.tables WHERE table_schema = '%s' AND table_name = '%s' )`
+		return fmt.Sprintf(q, schemaName, tableName)
+	}
+	q := `SELECT EXISTS ( SELECT 1 FROM information_schema.tables WHERE (database() IS NULL OR table_schema = database()) AND table_name = '%s' )`
+	return fmt.Sprintf(q, tableName)
+}

internal/dialect/dialectquery/postgres.go

@@ -2,7 +2,6 @@ package dialectquery
 
 import (
 	"fmt"
-	"strings"
 )
 
 type Postgres struct{}
@@ -53,11 +52,3 @@ func (p *Postgres) TableExists(tableName string) string {
 	q := `SELECT EXISTS ( SELECT 1 FROM pg_tables WHERE (current_schema() IS NULL OR schemaname = current_schema()) AND tablename = '%s' )`
 	return fmt.Sprintf(q, tableName)
 }
-
-func parseTableIdentifier(name string) (schema, table string) {
-	schema, table, found := strings.Cut(name, ".")
-	if !found {
-		return "", name
-	}
-	return schema, table
-}