Fix failure with initplans used conditionally during EvalPlanQual rechecks.

The EvalPlanQual machinery assumes that any initplans (that is,
uncorrelated sub-selects) used during an EPQ recheck would have already
been evaluated during the main query; this is implicit in the fact that
execPlan pointers are not copied into the EPQ estate's es_param_exec_vals.
But it's possible for that assumption to fail, if the initplan is only
reached conditionally.  For example, a sub-select inside a CASE expression
could be reached during a recheck when it had not been previously, if the
CASE test depends on a column that was just updated.

This bug is old, appearing to date back to my rewrite of EvalPlanQual in
commit 9f2ee8f28, but was not detected until Kyle Samson reported a case.

To fix, force all not-yet-evaluated initplans used within the EPQ plan
subtree to be evaluated at the start of the recheck, before entering the
EPQ environment.  This could be inefficient, if such an initplan is
expensive and goes unused again during the recheck --- but that's piling
one layer of improbability atop another.  It doesn't seem worth adding
more complexity to prevent that, at least not in the back branches.

It was convenient to use the new-in-v11 ExecEvalParamExecParams function
to implement this, but I didn't like either its name or the specifics of
its API, so revise that.

Back-patch all the way.  Rather than rewrite the patch to avoid depending
on bms_next_member() in the oldest branches, I chose to back-patch that
function into 9.4 and 9.3.  (This isn't the first time back-patches have
needed that, and it exhausted my patience.)  I also chose to back-patch
some test cases added by commits 71404af2a and 342a1ffa2 into 9.4 and 9.3,
so that the 9.x versions of eval-plan-qual.spec are all the same.

Andrew Gierth diagnosed the problem and contributed the added test cases,
though the actual code changes are by me.

Discussion: https://postgr.es/m/A033A40A-B234-4324-BE37-272279F7B627@tripadvisor.com

2 files changed, 48 insertions, 0 deletions

diff --git a/src/test/isolation/expected/eval-plan-qual.out b/src/test/isolation/expected/eval-plan-qual.out
index 9bbfdc1b5d6..49b3fb34469 100644
--- a/src/test/isolation/expected/eval-plan-qual.out
+++ b/src/test/isolation/expected/eval-plan-qual.out
@@ -184,6 +184,37 @@ ta_id          ta_value       tb_row
 1              newTableAValue (1,tableBValue)
 step c2: COMMIT;
 
+starting permutation: updateforcip updateforcip2 c1 c2 read_a
+step updateforcip: 
+	UPDATE table_a SET value = NULL WHERE id = 1;
+
+step updateforcip2: 
+	UPDATE table_a SET value = COALESCE(value, (SELECT text 'newValue')) WHERE id = 1;
+ <waiting ...>
+step c1: COMMIT;
+step updateforcip2: <... completed>
+step c2: COMMIT;
+step read_a: SELECT * FROM table_a ORDER BY id;
+id             value          
+
+1              newValue       
+
+starting permutation: updateforcip updateforcip3 c1 c2 read_a
+step updateforcip: 
+	UPDATE table_a SET value = NULL WHERE id = 1;
+
+step updateforcip3: 
+	WITH d(val) AS (SELECT text 'newValue' FROM generate_series(1,1))
+	UPDATE table_a SET value = COALESCE(value, (SELECT val FROM d)) WHERE id = 1;
+ <waiting ...>
+step c1: COMMIT;
+step updateforcip3: <... completed>
+step c2: COMMIT;
+step read_a: SELECT * FROM table_a ORDER BY id;
+id             value          
+
+1              newValue       
+
 starting permutation: wrtwcte readwcte c1 c2
 step wrtwcte: UPDATE table_a SET value = 'tableAValue2' WHERE id = 1;
 step readwcte: 
diff --git a/src/test/isolation/specs/eval-plan-qual.spec b/src/test/isolation/specs/eval-plan-qual.spec
index 0b70ad55ba1..367922de751 100644
--- a/src/test/isolation/specs/eval-plan-qual.spec
+++ b/src/test/isolation/specs/eval-plan-qual.spec
@@ -92,6 +92,13 @@ step "updateforss"	{
 	UPDATE table_b SET value = 'newTableBValue' WHERE id = 1;
 }
 
+# these tests exercise EvalPlanQual with conditional InitPlans which
+# have not been executed prior to the EPQ
+
+step "updateforcip"	{
+	UPDATE table_a SET value = NULL WHERE id = 1;
+}
+
 # these tests exercise mark/restore during EPQ recheck, cf bug #15032
 
 step "selectjoinforupdate"	{
@@ -129,6 +136,13 @@ step "readforss"	{
 	FROM table_a ta
 	WHERE ta.id = 1 FOR UPDATE OF ta;
 }
+step "updateforcip2"	{
+	UPDATE table_a SET value = COALESCE(value, (SELECT text 'newValue')) WHERE id = 1;
+}
+step "updateforcip3"	{
+	WITH d(val) AS (SELECT text 'newValue' FROM generate_series(1,1))
+	UPDATE table_a SET value = COALESCE(value, (SELECT val FROM d)) WHERE id = 1;
+}
 step "wrtwcte"	{ UPDATE table_a SET value = 'tableAValue2' WHERE id = 1; }
 step "wrjt"	{ UPDATE jointest SET data = 42 WHERE id = 7; }
 step "c2"	{ COMMIT; }
@@ -137,6 +151,7 @@ session "s3"
 setup		{ BEGIN ISOLATION LEVEL READ COMMITTED; }
 step "read"	{ SELECT * FROM accounts ORDER BY accountid; }
 step "read_ext"	{ SELECT * FROM accounts_ext ORDER BY accountid; }
+step "read_a"	{ SELECT * FROM table_a ORDER BY id; }
 
 # this test exercises EvalPlanQual with a CTE, cf bug #14328
 step "readwcte"	{
@@ -171,6 +186,8 @@ permutation "wx2" "partiallock" "c2" "c1" "read"
 permutation "wx2" "lockwithvalues" "c2" "c1" "read"
 permutation "wx2_ext" "partiallock_ext" "c2" "c1" "read_ext"
 permutation "updateforss" "readforss" "c1" "c2"
+permutation "updateforcip" "updateforcip2" "c1" "c2" "read_a"
+permutation "updateforcip" "updateforcip3" "c1" "c2" "read_a"
 permutation "wrtwcte" "readwcte" "c1" "c2"
 permutation "wrjt" "selectjoinforupdate" "c2" "c1"
 permutation "wrtwcte" "multireadwcte" "c1" "c2"