Improve ruleutils' printout of LATERAL references within subplans.

Commit 1cc29fe7c, which taught EXPLAIN to print PARAM_EXEC Params as
the referenced expressions, included some checks to prevent matching
Params found in SubPlans or InitPlans to NestLoopParams of upper query
levels.  At the time, this seemed possibly necessary to avoid false
matches because of the planner's habit of re-using the same PARAM_EXEC
slot in multiple places in a plan.  Furthermore, in the absence of
LATERAL no such reference could be valid anyway.  But it's possible
now that we have LATERAL, and in the wake of 46c508fbc and 1db5667ba
I believe the false-match hazard is gone.  Hence, remove the
in_same_plan_level checks.  As shown in the regression test changes,
this provides a useful improvement in readability for EXPLAIN of
LATERAL-using subplans.

Richard Guo, reviewed by Greg Stark and myself

Discussion: https://postgr.es/m/CAMbWs4-YSOcQXAagJetP95cAeZPqzOy5kM5yijG0PVW5ztRb4w@mail.gmail.com

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index c5a49d0be34258fac09213941b762cd1b5bbd816..b4c040758874190eb6ea5419ce81716a4199aec2 100644 (file)
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7896,12 +7896,10 @@ find_param_referent(Param *param, deparse_context *context,
    {
        deparse_namespace *dpns;
        Plan       *child_plan;
-       bool        in_same_plan_level;
        ListCell   *lc;
 
        dpns = (deparse_namespace *) linitial(context->namespaces);
        child_plan = dpns->plan;
-       in_same_plan_level = true;
 
        foreach(lc, dpns->ancestors)
        {
@@ -7909,13 +7907,10 @@ find_param_referent(Param *param, deparse_context *context,
            ListCell   *lc2;
 
            /*
-            * NestLoops transmit params to their inner child only; also, once
-            * we've crawled up out of a subplan, this couldn't possibly be
-            * the right match.
+            * NestLoops transmit params to their inner child only.
             */
            if (IsA(ancestor, NestLoop) &&
-               child_plan == innerPlan(ancestor) &&
-               in_same_plan_level)
+               child_plan == innerPlan(ancestor))
            {
                NestLoop   *nl = (NestLoop *) ancestor;
 
@@ -7973,34 +7968,14 @@ find_param_referent(Param *param, deparse_context *context,
                    }
                }
 
-               /* We have emerged from a subplan. */
-               in_same_plan_level = false;
-
                /* SubPlan isn't a kind of Plan, so skip the rest */
                continue;
            }
 
            /*
-            * Check to see if we're emerging from an initplan of the current
-            * ancestor plan.  Initplans never have any parParams, so no need
-            * to search that list, but we need to know if we should reset
-            * in_same_plan_level.
+            * We need not consider the ancestor's initPlan list, since
+            * initplans never have any parParams.
             */
-           foreach(lc2, ((Plan *) ancestor)->initPlan)
-           {
-               SubPlan    *subplan = lfirst_node(SubPlan, lc2);
-
-               if (child_plan != (Plan *) list_nth(dpns->subplans,
-                                                   subplan->plan_id - 1))
-                   continue;
-
-               /* No parameters to be had here. */
-               Assert(subplan->parParam == NIL);
-
-               /* We have emerged from an initplan. */
-               in_same_plan_level = false;
-               break;
-           }
 
            /* No luck, crawl up to next ancestor */
            child_plan = (Plan *) ancestor;

diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 93583710725b0a075edbcf782eb5ef395e7c5d10..80638d84a043593826f3892e12e963f41d29aa16 100644 (file)
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -6074,8 +6074,8 @@ lateral (select * from int8_tbl t1,
                                      where q2 = (select greatest(t1.q1,t2.q2))
                                        and (select v.id=0)) offset 0) ss2) ss
          where t1.q1 = ss.q2) ss0;
-                           QUERY PLAN                            
------------------------------------------------------------------
+                              QUERY PLAN                              
+----------------------------------------------------------------------
  Nested Loop
    Output: "*VALUES*".column1, t1.q1, t1.q2, ss2.q1, ss2.q2
    ->  Seq Scan on public.int8_tbl t1
@@ -6096,10 +6096,10 @@ lateral (select * from int8_tbl t1,
                              One-Time Filter: $4
                              InitPlan 1 (returns $2)
                                ->  Result
-                                     Output: GREATEST($0, t2.q2)
+                                     Output: GREATEST(t1.q1, t2.q2)
                              InitPlan 2 (returns $4)
                                ->  Result
-                                     Output: ($3 = 0)
+                                     Output: ("*VALUES*".column1 = 0)
                              ->  Seq Scan on public.int8_tbl t3
                                    Output: t3.q1, t3.q2
                                    Filter: (t3.q2 = $2)

diff --git a/src/test/regress/expected/subselect.out b/src/test/regress/expected/subselect.out
index 63d26d44fc3b3017445fc3acf5bf1e70516a51bf..22af8fafa173b868273138dd6b63c1d2462b01ff 100644 (file)
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -1155,7 +1155,7 @@ where o.ten = 0;
                SubPlan 1
                  ->  Seq Scan on public.int4_tbl
                        Output: int4_tbl.f1
-                       Filter: (int4_tbl.f1 <= $0)
+                       Filter: (int4_tbl.f1 <= o.hundred)
 (14 rows)
 
 select sum(ss.tst::int) from