add support for table hint in multi-table MySQL DELETE queries

doug-martin · Mar 5, 2021 · b65f65c · b65f65c
1 parent ee815b3
commit b65f65c
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Showing 3 changed files with 11 additions and 2 deletions.
diff --git a/dialect/mysql/mysql.go b/dialect/mysql/mysql.go
@@ -20,6 +20,7 @@ func DialectOptions() *goqu.SQLDialectOptions {
 	opts.SupportsWithCTERecursive = false
 	opts.SupportsDistinctOn = false
 	opts.SupportsWindowFunction = false
+	opts.SupportsDeleteTableHint = true
 
 	opts.UseFromClauseForMultipleUpdateTables = false
 

diff --git a/sqlgen/delete_sql_generator.go b/sqlgen/delete_sql_generator.go
@@ -46,7 +46,9 @@ func (dsg *deleteSQLGenerator) Generate(b sb.SQLBuilder, clauses exp.DeleteClaus
 		case CommonTableSQLFragment:
 			dsg.esg.Generate(b, clauses.CommonTables())
 		case DeleteBeginSQLFragment:
-			dsg.DeleteBeginSQL(b)
+			dsg.DeleteBeginSQL(
+				b, exp.NewColumnListExpression(clauses.From()), !(clauses.HasLimit() || clauses.HasOrder()),
+			)
 		case FromSQLFragment:
 			dsg.FromSQL(b, exp.NewColumnListExpression(clauses.From()))
 		case WhereSQLFragment:
@@ -68,6 +70,9 @@ func (dsg *deleteSQLGenerator) Generate(b sb.SQLBuilder, clauses exp.DeleteClaus
 }
 
 // Adds the correct fragment to being an DELETE statement
-func (dsg *deleteSQLGenerator) DeleteBeginSQL(b sb.SQLBuilder) {
+func (dsg *deleteSQLGenerator) DeleteBeginSQL(b sb.SQLBuilder, from exp.ColumnListExpression, multiTable bool) {
 	b.Write(dsg.dialectOptions.DeleteClause)
+	if multiTable && dsg.dialectOptions.SupportsDeleteTableHint {
+		dsg.SourcesSQL(b, from)
+	}
 }
diff --git a/sqlgen/sql_dialect_options.go b/sqlgen/sql_dialect_options.go
@@ -12,6 +12,8 @@ type (
 	SQLDialectOptions struct {
 		// Set to true if the dialect supports ORDER BY expressions in DELETE statements (DEFAULT=false)
 		SupportsOrderByOnDelete bool
+		// Set to true if the dialect supports table hint for DELETE statements (DELETE t FROM t ...), DEFAULT=false
+		SupportsDeleteTableHint bool
 		// Set to true if the dialect supports ORDER BY expressions in UPDATE statements (DEFAULT=false)
 		SupportsOrderByOnUpdate bool
 		// Set to true if the dialect supports LIMIT expressions in DELETE statements (DEFAULT=false)
@@ -395,6 +397,7 @@ func (sf SQLFragmentType) String() string {
 func DefaultDialectOptions() *SQLDialectOptions {
 	return &SQLDialectOptions{
 		SupportsOrderByOnDelete:     false,
+		SupportsDeleteTableHint:     false,
 		SupportsOrderByOnUpdate:     false,
 		SupportsLimitOnDelete:       false,
 		SupportsLimitOnUpdate:       false,