planner fix: only expose columns being returned from the RHS

Signed-off-by: Andres Taylor <andres@planetscale.com>

Author: systay

go/vt/vtgate/planbuilder/operators/projection_pushing.go

@@ -324,11 +324,18 @@ func exposeColumnsThroughDerivedTable(ctx *plancontext.PlanningContext, p *Proje
 
 	lhsIDs := TableID(src.LHS)
 	rhsIDs := TableID(src.RHS)
-	rewriteColumnsForJoin(ctx, src.JoinPredicates.columns, lhsIDs, rhsIDs, lhs, rhs)
-	rewriteColumnsForJoin(ctx, src.JoinColumns.columns, lhsIDs, rhsIDs, lhs, rhs)
+	rewriteColumnsForJoin(ctx, src.JoinPredicates.columns, lhsIDs, rhsIDs, lhs, rhs, false)
+	rewriteColumnsForJoin(ctx, src.JoinColumns.columns, lhsIDs, rhsIDs, lhs, rhs, true)
 }
 
-func rewriteColumnsForJoin(ctx *plancontext.PlanningContext, columns []applyJoinColumn, lhsIDs, rhsIDs semantics.TableSet, lhs, rhs *projector) {
+func rewriteColumnsForJoin(
+	ctx *plancontext.PlanningContext,
+	columns []applyJoinColumn,
+	lhsIDs, rhsIDs semantics.TableSet,
+	lhs, rhs *projector,
+	exposeRHS bool, // we only want to expose the returned columns from the RHS.
+	// For predicates, we don't need to expose the RHS columns
+) {
 	for colIdx, predicate := range columns {
 		for lhsIdx, bve := range predicate.LHSExprs {
 			// since this is on the LHSExprs, we know that dependencies are from that side of the join
@@ -353,7 +360,9 @@ func rewriteColumnsForJoin(ctx *plancontext.PlanningContext, columns []applyJoin
 				rewriteTo = lhs.get(ctx, expr)
 				return false
 			case deps.IsSolvedBy(rhsIDs):
-				rewriteTo = rhs.get(ctx, expr)
+				if exposeRHS {
+					rewriteTo = rhs.get(ctx, expr)
+				}
 				return false
 			default:
 				return true

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

@@ -1133,8 +1133,8 @@
               "Name": "user",
               "Sharded": true
             },
-            "FieldQuery": "select 1 from (select user_extra.col as `user_extra.col` from user_extra where 1 != 1) as t where 1 != 1",
-            "Query": "select 1 from (select user_extra.col as `user_extra.col` from user_extra where user_extra.col = :user_col) as t",
+            "FieldQuery": "select 1 from user_extra where 1 != 1",
+            "Query": "select 1 from user_extra where user_extra.col = :user_col",
             "Table": "user_extra"
           }
         ]

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

@@ -1901,8 +1901,8 @@
               "Name": "user",
               "Sharded": true
             },
-            "FieldQuery": "select 1 from (select user_extra.col as `user_extra.col` from user_extra where 1 != 1) as t where 1 != 1",
-            "Query": "select 1 from (select user_extra.col as `user_extra.col` from user_extra where user_extra.col = :user_col) as t",
+            "FieldQuery": "select 1 from user_extra where 1 != 1",
+            "Query": "select 1 from user_extra where user_extra.col = :user_col",
             "Table": "user_extra"
           }
         ]
@@ -4296,7 +4296,7 @@
                   {
                     "OperatorType": "Join",
                     "Variant": "Join",
-                    "JoinColumnIndexes": "R:0,L:1,R:2",
+                    "JoinColumnIndexes": "R:0,L:1,R:1",
                     "JoinVars": {
                       "m_id": 0
                     },
@@ -4320,8 +4320,8 @@
                           "Name": "user",
                           "Sharded": true
                         },
-                        "FieldQuery": "select subquery_for_count.user_id, subquery_for_count.`u.id`, weight_string(subquery_for_count.user_id) from (select u.user_id, u.id as `u.id` from `user` as u, user_extra as ue where 1 != 1) as subquery_for_count where 1 != 1",
-                        "Query": "select distinct subquery_for_count.user_id, subquery_for_count.`u.id`, weight_string(subquery_for_count.user_id) from (select u.user_id, u.id as `u.id` from `user` as u, user_extra as ue where u.id = :m_id and u.id = ue.user_id) as subquery_for_count",
+                        "FieldQuery": "select subquery_for_count.user_id, weight_string(subquery_for_count.user_id) from (select u.user_id from `user` as u, user_extra as ue where 1 != 1) as subquery_for_count where 1 != 1",
+                        "Query": "select distinct subquery_for_count.user_id, weight_string(subquery_for_count.user_id) from (select u.user_id from `user` as u, user_extra as ue where u.id = :m_id and u.id = ue.user_id) as subquery_for_count",
                         "Table": "`user`, user_extra",
                         "Values": [
                           ":m_id"

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

@@ -643,8 +643,8 @@
                                       "Name": "main",
                                       "Sharded": true
                                     },
-                                    "FieldQuery": "select count(*), shipping.o_custkey from (select o_custkey as o_custkey, o_orderkey as o_orderkey from orders where 1 != 1) as shipping where 1 != 1 group by shipping.o_custkey",
-                                    "Query": "select count(*), shipping.o_custkey from (select o_custkey as o_custkey, o_orderkey as o_orderkey from orders where o_orderkey = :l_orderkey) as shipping group by shipping.o_custkey",
+                                    "FieldQuery": "select count(*), shipping.o_custkey from (select o_custkey as o_custkey from orders where 1 != 1) as shipping where 1 != 1 group by shipping.o_custkey",
+                                    "Query": "select count(*), shipping.o_custkey from (select o_custkey as o_custkey from orders where o_orderkey = :l_orderkey) as shipping group by shipping.o_custkey",
                                     "Table": "orders",
                                     "Values": [
                                       ":l_orderkey"
@@ -679,8 +679,8 @@
                                       "Name": "main",
                                       "Sharded": true
                                     },
-                                    "FieldQuery": "select count(*), shipping.s_nationkey from (select s_suppkey as s_suppkey, s_nationkey as s_nationkey from supplier where 1 != 1) as shipping where 1 != 1 group by shipping.s_nationkey",
-                                    "Query": "select count(*), shipping.s_nationkey from (select s_suppkey as s_suppkey, s_nationkey as s_nationkey from supplier where s_suppkey = :l_suppkey) as shipping group by shipping.s_nationkey",
+                                    "FieldQuery": "select count(*), shipping.s_nationkey from (select s_nationkey as s_nationkey from supplier where 1 != 1) as shipping where 1 != 1 group by shipping.s_nationkey",
+                                    "Query": "select count(*), shipping.s_nationkey from (select s_nationkey as s_nationkey from supplier where s_suppkey = :l_suppkey) as shipping group by shipping.s_nationkey",
                                     "Table": "supplier",
                                     "Values": [
                                       ":l_suppkey"
@@ -694,8 +694,8 @@
                                       "Name": "main",
                                       "Sharded": true
                                     },
-                                    "FieldQuery": "select count(*), supp_nation, weight_string(supp_nation), n1.n_nationkey as `n1.n_nationkey` from (select n1.n_name as supp_nation, n1.n_name = 'FRANCE' as `n1.n_name = 'FRANCE'`, n1.n_name = 'GERMANY' as `n1.n_name = 'GERMANY'`, n1.n_nationkey as `n1.n_nationkey` from nation as n1 where 1 != 1) as shipping where 1 != 1 group by supp_nation, weight_string(supp_nation)",
-                                    "Query": "select count(*), supp_nation, weight_string(supp_nation), n1.n_nationkey as `n1.n_nationkey` from (select n1.n_name as supp_nation, n1.n_name = 'FRANCE' as `n1.n_name = 'FRANCE'`, n1.n_name = 'GERMANY' as `n1.n_name = 'GERMANY'`, n1.n_nationkey as `n1.n_nationkey` from nation as n1 where n1.n_nationkey = :s_nationkey) as shipping group by supp_nation, weight_string(supp_nation)",
+                                    "FieldQuery": "select count(*), supp_nation, weight_string(supp_nation) from (select n1.n_name as supp_nation, n1.n_name = 'FRANCE' as `n1.n_name = 'FRANCE'`, n1.n_name = 'GERMANY' as `n1.n_name = 'GERMANY'` from nation as n1 where 1 != 1) as shipping where 1 != 1 group by supp_nation, weight_string(supp_nation)",
+                                    "Query": "select count(*), supp_nation, weight_string(supp_nation) from (select n1.n_name as supp_nation, n1.n_name = 'FRANCE' as `n1.n_name = 'FRANCE'`, n1.n_name = 'GERMANY' as `n1.n_name = 'GERMANY'` from nation as n1 where n1.n_nationkey = :s_nationkey) as shipping group by supp_nation, weight_string(supp_nation)",
                                     "Table": "nation",
                                     "Values": [
                                       ":s_nationkey"
@@ -734,8 +734,8 @@
                               "Name": "main",
                               "Sharded": true
                             },
-                            "FieldQuery": "select count(*), shipping.c_nationkey from (select c_custkey as c_custkey, c_nationkey as c_nationkey from customer where 1 != 1) as shipping where 1 != 1 group by shipping.c_nationkey",
-                            "Query": "select count(*), shipping.c_nationkey from (select c_custkey as c_custkey, c_nationkey as c_nationkey from customer where c_custkey = :o_custkey) as shipping group by shipping.c_nationkey",
+                            "FieldQuery": "select count(*), shipping.c_nationkey from (select c_nationkey as c_nationkey from customer where 1 != 1) as shipping where 1 != 1 group by shipping.c_nationkey",
+                            "Query": "select count(*), shipping.c_nationkey from (select c_nationkey as c_nationkey from customer where c_custkey = :o_custkey) as shipping group by shipping.c_nationkey",
                             "Table": "customer",
                             "Values": [
                               ":o_custkey"
@@ -749,8 +749,8 @@
                               "Name": "main",
                               "Sharded": true
                             },
-                            "FieldQuery": "select count(*), cust_nation, weight_string(cust_nation), n2.n_nationkey as `n2.n_nationkey` from (select n2.n_name as cust_nation, n2.n_name = 'GERMANY' as `n2.n_name = 'GERMANY'`, n2.n_name = 'FRANCE' as `n2.n_name = 'FRANCE'`, n2.n_nationkey as `n2.n_nationkey` from nation as n2 where 1 != 1) as shipping where 1 != 1 group by cust_nation, weight_string(cust_nation)",
-                            "Query": "select count(*), cust_nation, weight_string(cust_nation), n2.n_nationkey as `n2.n_nationkey` from (select n2.n_name as cust_nation, n2.n_name = 'GERMANY' as `n2.n_name = 'GERMANY'`, n2.n_name = 'FRANCE' as `n2.n_name = 'FRANCE'`, n2.n_nationkey as `n2.n_nationkey` from nation as n2 where (:n1_n_name = 'FRANCE' and n2.n_name = 'GERMANY' or :n1_n_name = 'GERMANY' and n2.n_name = 'FRANCE') and n2.n_nationkey = :c_nationkey) as shipping group by cust_nation, weight_string(cust_nation)",
+                            "FieldQuery": "select count(*), cust_nation, weight_string(cust_nation) from (select n2.n_name as cust_nation from nation as n2 where 1 != 1) as shipping where 1 != 1 group by cust_nation, weight_string(cust_nation)",
+                            "Query": "select count(*), cust_nation, weight_string(cust_nation) from (select n2.n_name as cust_nation from nation as n2 where (:n1_n_name = 'FRANCE' and n2.n_name = 'GERMANY' or :n1_n_name = 'GERMANY' and n2.n_name = 'FRANCE') and n2.n_nationkey = :c_nationkey) as shipping group by cust_nation, weight_string(cust_nation)",
                             "Table": "nation",
                             "Values": [
                               ":c_nationkey"