Faster MySQL GetTableColumnsMetaData query

generator/mysql/query_set.go

@@ -39,27 +39,36 @@ ORDER BY table_name;
 
 func (m mySqlQuerySet) GetTableColumnsMetaData(db *sql.DB, schemaName string, tableName string) ([]metadata.Column, error) {
 	query := `
-SELECT COLUMN_NAME AS "column.Name", 
+SELECT
-	IS_NULLABLE = "YES" AS "column.IsNullable",
+		col.COLUMN_NAME AS "column.Name",
-	columns.COLUMN_COMMENT as "column.Comment",
+		col.IS_NULLABLE = "YES" AS "column.IsNullable",
-	(EXISTS(
+		col.COLUMN_COMMENT AS "column.Comment",
-		SELECT 1
+		pk.IsPrimaryKey AS "column.IsPrimaryKey",
+		IF (col.COLUMN_TYPE = 'tinyint(1)',
+				'boolean',
+				IF (col.DATA_TYPE = 'enum',
+						CONCAT(col.TABLE_NAME, '_', col.COLUMN_NAME),
+						col.DATA_TYPE)
+		) AS "dataType.Name",
+		IF (col.DATA_TYPE = 'enum', 'enum', 'base') AS "dataType.Kind",
+		col.COLUMN_TYPE LIKE '%unsigned%' AS "dataType.IsUnsigned"
+FROM
+		information_schema.columns AS col
+LEFT JOIN (
+		SELECT k.column_name, 1 AS IsPrimaryKey
 		FROM information_schema.table_constraints t
 		JOIN information_schema.key_column_usage k USING(constraint_name, table_schema, table_name)
-		WHERE table_schema = ? AND table_name = ? AND t.constraint_type='PRIMARY KEY' AND k.column_name = columns.column_name
+		WHERE t.table_schema =  ?
-	)) AS "column.IsPrimaryKey",
+			AND t.table_name = ?
-	IF (COLUMN_TYPE = 'tinyint(1)', 
+			AND t.constraint_type = 'PRIMARY KEY'
-			'boolean', 
+) AS pk ON col.COLUMN_NAME = pk.column_name
-			IF (DATA_TYPE='enum', 
+WHERE
-					CONCAT(TABLE_NAME, '_', COLUMN_NAME), 
+		col.table_schema = ?
-					DATA_TYPE)
+		AND col.table_name = ?
-	) AS "dataType.Name", 
+ORDER BY
-	IF (DATA_TYPE = 'enum', 'enum', 'base') AS "dataType.Kind", 
+		col.ordinal_position;
-	COLUMN_TYPE LIKE '%unsigned%' AS "dataType.IsUnsigned"
-FROM information_schema.columns
-WHERE table_schema = ? AND table_name = ?
-ORDER BY ordinal_position;
 	`
+
 	var columns []metadata.Column
 	_, err := qrm.Query(context.Background(), db, query, []interface{}{schemaName, tableName, schemaName, tableName}, &columns)
 	if err != nil {