[#21266] YSQL: Make BNL hashtable have its own Expression Context

Summary:
Before this change, the BNL hashtable used the per-tuple expression context in the execution state to compute its equality expressions. This would yield issues like in queries like the one in the added test case. In such queries where the hashtable's equality expression is a subplan that might also use the same execution state's expression context, the expression execution would overwrite any data that the hashtable code had written into its expression context. This problem would most obviously happen in cases where the underlying subplan expression also ended up using a BNL hashtable that used the same inherited expression context.
This diff makes the hashtable BNL have its own expression context that's created using `CreateExprContext` just like `nodeHash.c` or `nodeMergejoin.c` might.

Needs backports to 2024.1, 2.20, 2.18
Jira: DB-10184

Test Plan: ./yb_build.sh --java-test 'org.yb.pgsql.TestPgRegressJoin'

Reviewers: mtakahara

Reviewed By: mtakahara

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D34889

src/postgres/src/backend/executor/nodeYbBatchedNestloop.c

@@ -453,7 +453,7 @@ InitHash(YbBatchedNestLoopState *bnlstate)
 {
 	EState *estate = bnlstate->js.ps.state;
 	YbBatchedNestLoop *plan = (YbBatchedNestLoop*) bnlstate->js.ps.plan;
-	ExprContext *econtext = GetPerTupleExprContext(estate);
+	ExprContext *econtext = CreateExprContext(estate);
 	TupleDesc outer_tdesc = outerPlanState(bnlstate)->ps_ResultTupleDesc;
 
 	Assert(UseHash(plan, bnlstate));

src/postgres/src/test/regress/expected/yb_join_batching.out

@@ -2266,6 +2266,67 @@ WHERE ss1.a = ss3.a and ss3.c <= (SELECT a FROM ss3 where a < ss2.a + ss1.a limi
 DROP TABLE ss1;
 DROP TABLE ss2;
 DROP TABLE ss3;
+CREATE TABLE other(a int);
+CREATE INDEX ON other(a asc);
+CREATE TABLE ss1(a int);
+CREATE TABLE ss2(a int, b int);
+CREATE INDEX ON ss2(a asc, b asc);
+INSERT INTO ss1 VALUES (0), (0);
+INSERT INTO ss2 VALUES (0, 0), (0, 0);
+INSERT INTO other VALUES (1), (1);
+/*+Set(enable_hashjoin OFF) Set(enable_mergejoin OFF) Set(enable_material OFF) */EXPLAIN (COSTS OFF)
+SELECT *
+FROM (
+    SELECT ss1.a as a, other.a as othera
+    FROM ss1
+    CROSS JOIN other
+) AS cross_join
+LEFT OUTER JOIN ss2 ON ss2.a = (
+    SELECT other.a
+    FROM other, ss1
+    WHERE other.a = ss1.a + cross_join.a limit 1
+);
+                                                   QUERY PLAN
+----------------------------------------------------------------------------------------------------------------
+ Nested Loop
+   ->  YB Batched Nested Loop Left Join
+         Join Filter: (ss2.a = (SubPlan 1))
+         ->  Seq Scan on ss1
+         ->  Index Only Scan using ss2_a_b_idx on ss2
+               Index Cond: (a = ANY (ARRAY[(SubPlan 1), (SubPlan 1), (SubPlan 1)]))
+               SubPlan 1
+                 ->  Limit
+                       ->  YB Batched Nested Loop Join
+                             Join Filter: (other_1.a = (ss1_1.a + ss1.a))
+                             ->  Seq Scan on ss1 ss1_1
+                             ->  Index Only Scan using other_a_idx on other other_1
+                                   Index Cond: (a = ANY (ARRAY[(ss1_1.a + ss1.a), ($2 + ss1.a), ($3 + ss1.a)]))
+   ->  Index Only Scan using other_a_idx on other
+(14 rows)
+
+/*+Set(enable_hashjoin OFF) Set(enable_mergejoin OFF) Set(enable_material OFF) */
+SELECT *
+FROM (
+    SELECT ss1.a as a, other.a as othera
+    FROM ss1
+    CROSS JOIN other
+) AS cross_join
+LEFT OUTER JOIN ss2 ON ss2.a = (
+    SELECT other.a
+    FROM other, ss1
+    WHERE other.a = ss1.a + cross_join.a limit 1
+);
+ a | othera | a | b
+---+--------+---+---
+ 0 |      1 |   |
+ 0 |      1 |   |
+ 0 |      1 |   |
+ 0 |      1 |   |
+(4 rows)
+
+DROP TABLE other;
+DROP TABLE ss1;
+DROP TABLE ss2;
 --
 --
 -- Inner joins (equi-joins)

src/postgres/src/test/regress/sql/yb_join_batching.sql

@@ -670,6 +670,46 @@ DROP TABLE ss1;
 DROP TABLE ss2;
 DROP TABLE ss3;
 
+CREATE TABLE other(a int);
+CREATE INDEX ON other(a asc);
+CREATE TABLE ss1(a int);
+CREATE TABLE ss2(a int, b int);
+CREATE INDEX ON ss2(a asc, b asc);
+
+INSERT INTO ss1 VALUES (0), (0);
+INSERT INTO ss2 VALUES (0, 0), (0, 0);
+INSERT INTO other VALUES (1), (1);
+
+/*+Set(enable_hashjoin OFF) Set(enable_mergejoin OFF) Set(enable_material OFF) */EXPLAIN (COSTS OFF)
+SELECT *
+FROM (
+    SELECT ss1.a as a, other.a as othera
+    FROM ss1
+    CROSS JOIN other
+) AS cross_join
+LEFT OUTER JOIN ss2 ON ss2.a = (
+    SELECT other.a
+    FROM other, ss1
+    WHERE other.a = ss1.a + cross_join.a limit 1
+);
+
+/*+Set(enable_hashjoin OFF) Set(enable_mergejoin OFF) Set(enable_material OFF) */
+SELECT *
+FROM (
+    SELECT ss1.a as a, other.a as othera
+    FROM ss1
+    CROSS JOIN other
+) AS cross_join
+LEFT OUTER JOIN ss2 ON ss2.a = (
+    SELECT other.a
+    FROM other, ss1
+    WHERE other.a = ss1.a + cross_join.a limit 1
+);
+
+DROP TABLE other;
+DROP TABLE ss1;
+DROP TABLE ss2;
+
 --
 --
 -- Inner joins (equi-joins)