[release-20.0] Fix subquery planning having an aggregation that is us…

…ed in order by as long as we can merge it all into a single route (#16402) (#16408)

Signed-off-by: Manan Gupta <manan@planetscale.com>
Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>

go/vt/vtgate/planbuilder/operators/horizon_expanding.go

@@ -141,13 +141,18 @@ func expandOrderBy(ctx *plancontext.PlanningContext, op Operator, qp *QueryProje
  continue
  }
 
- // If the operator is not a projection, we cannot handle subqueries with aggregation
+ // If the operator is not a projection, we cannot handle subqueries with aggregation if we are unable to push everything into a single route.
  if !ok {
- panic(vterrors.VT12001("subquery with aggregation in order by"))
+ ctx.SemTable.NotSingleRouteErr = vterrors.VT12001("subquery with aggregation in order by")
+ return &Ordering{
+ Source: op,
+ Order: qp.OrderExprs,
+ }
+ } else {
+ // Add the new subquery expression to the projection
+ proj.addSubqueryExpr(ctx, aeWrap(newExpr), newExpr, subqs...)
  }
 
- // Add the new subquery expression to the projection
- proj.addSubqueryExpr(ctx, aeWrap(newExpr), newExpr, subqs...)
  // Replace the original order expression with the new expression containing subqueries
  newOrder = append(newOrder, OrderBy{
  Inner: &sqlparser.Order{

go/vt/vtgate/planbuilder/testdata/select_cases.json

@@ -736,6 +736,33 @@
  ]
  }
  },
+ {
+ "comment": "subquery with an aggregation in order by that can be merged into a single route",
+ "query": "select col, trim((select user_name from user where id = 3)) val from user_extra where user_id = 3 group by col order by val",
+ "plan": {
+ "QueryType": "SELECT",
+ "Original": "select col, trim((select user_name from user where id = 3)) val from user_extra where user_id = 3 group by col order by val",
+ "Instructions": {
+ "OperatorType": "Route",
+ "Variant": "EqualUnique",
+ "Keyspace": {
+ "Name": "user",
+ "Sharded": true
+ },
+ "FieldQuery": "select col, trim((select user_name from `user` where 1 != 1)) as val from user_extra where 1 != 1 group by col",
+ "Query": "select col, trim((select user_name from `user` where id = 3)) as val from user_extra where user_id = 3 group by col order by trim((select `user`.user_name from `user` where `user`.id = 3)) asc",
+ "Table": "user_extra",
+ "Values": [
+ "3"
+ ],
+ "Vindex": "user_index"
+ },
+ "TablesUsed": [
+ "user.user",
+ "user.user_extra"
+ ]
+ }
+ },
  {
  "comment": "Jumbled references",
  "query": "select user.col, user_extra.id, user.col2 from user join user_extra",

go/vt/vtgate/planbuilder/testdata/unsupported_cases.json

@@ -24,6 +24,11 @@
  "query": "update user set id = 1 where id = 1",
  "plan": "VT12001: unsupported: you cannot UPDATE primary vindex columns; invalid update on vindex: user_index"
  },
+ {
+ "comment": "subquery with an aggregation in order by that cannot be merged into a single route",
+ "query": "select col, trim((select user_name from user where col = 'a')) val from user_extra where user_id = 3 group by col order by val",
+ "plan": "VT12001: unsupported: subquery with aggregation in order by"
+ },
  {
  "comment": "update change in multicol vindex column",
  "query": "update multicol_tbl set colc = 5, colb = 4 where cola = 1 and colb = 2",