On Tue, Sep 14, 2021 at 10:44 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com> writes: > I am getting "ERROR: subplan "SubPlan 1" was not initialized" error with > below test case.
> CREATE TABLE tbl ( c1 int, c2 int, c3 int ) PARTITION BY LIST (c1); > create table tbl_null PARTITION OF tbl FOR VALUES IN (null); > create table tbl_def PARTITION OF tbl DEFAULT; > insert into tbl values (8800,0,0); > insert into tbl values (1891,1,1); > insert into tbl values (3420,2,0); > insert into tbl values (9850,3,0); > insert into tbl values (7164,4,4); > analyze tbl; > explain (costs off) select count(*) from tbl t1 where (exists(select 1 from > tbl t2 where t2.c1 = t1.c2) or c3 < 0);
> postgres=# explain (costs off) select count(*) from tbl t1 where > (exists(select 1 from tbl t2 where t2.c1 = t1.c2) or c3 < 0); > ERROR: subplan "SubPlan 1" was not initialized
Nice example. This is failing since 41efb8340. It happens because we copy the AlternativeSubPlan for the EXISTS into the scan clauses for each of t1's partitions. At setrefs.c time, when fix_alternative_subplan() looks at the first of these AlternativeSubPlans, it decides it likes the first subplan better, so it deletes SubPlan 2 from the root->glob->subplans list. But when it comes to the next copy (which is attached to a partition with a different number of rows), it likes the second subplan better, so it deletes SubPlan 1 from the root->glob->subplans list. Now we have SubPlan nodes in the tree with no referents in the global list of subplans, so kaboom.
The easiest fix would just be to not try to delete unreferenced subplans. The error goes away if I remove the "lfirst(lc2) = NULL" statements from fix_alternative_subplan(). However, this is a bit annoying since then we will still pay the cost of initializing subplans that (in most cases) will never be used. I'm going to look into how painful it is to have setrefs.c remove unused subplans only at the end, after it's seen all the AlternativeSubPlans.
regards, tom lane
Hi,
In the fix, isUsedSubplan is used to tell whether any given subplan is used.
Since only one subplan is used, I wonder if the array can be replaced by specifying the subplan is used.
