feat: turn off the cost check before using hash joins. we'll just rel…

…y on the hint for now Signed-off-by: Andres Taylor <[email protected]>
vitessio · Nov 22, 2021 · 51b97da · 51b97da
1 parent cba1975
commit 51b97da
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Showing 2 changed files with 2 additions and 3 deletions.
diff --git a/go/vt/vtgate/planbuilder/gen4_planner.go b/go/vt/vtgate/planbuilder/gen4_planner.go
@@ -27,8 +27,6 @@ import (
 
 var _ selectPlanner = gen4Planner
 
-const MinHashJoinCost = 5
-
 func gen4Planner(query string) func(sqlparser.Statement, *sqlparser.ReservedVars, ContextVSchema) (engine.Primitive, error) {
 	return func(stmt sqlparser.Statement, reservedVars *sqlparser.ReservedVars, vschema ContextVSchema) (engine.Primitive, error) {
 		selStatement, ok := stmt.(sqlparser.SelectStatement)

diff --git a/go/vt/vtgate/planbuilder/querytree_transformers.go b/go/vt/vtgate/planbuilder/querytree_transformers.go
@@ -539,7 +539,8 @@ func transformJoinPlan(ctx *planningContext, n *joinTree) (logicalPlan, error) {
 // Hash joins are only supporting equality join predicates, which is why the join predicate
 // has to be an EqualOp.
 func canHashJoin(ctx *planningContext, n *joinTree) (canHash bool, lhs, rhs joinColumnInfo, err error) {
-	if len(n.predicatesToRemoveFromHashJoin) != 1 || n.rhs.cost() <= MinHashJoinCost || n.leftJoin ||
+	if len(n.predicatesToRemoveFromHashJoin) != 1 ||
+		n.leftJoin ||
 		!sqlparser.ExtractCommentDirectives(ctx.semTable.Comments).IsSet(sqlparser.DirectiveAllowHashJoin) {
 		return
 	}