Set query ID in parallel workers for vacuum, BRIN and btree

All these code paths use their own entry point when starting parallel
workers, but failed to set a query ID, even if they set a text query.
Hence, this data would be missed in pg_stat_activity for the worker
processes.  The main entry point for parallel query processing,
ParallelQueryMain(), is already doing that by saving its query ID in a
dummy PlannedStmt, but not the others.  The code is changed so as the
query ID of these queries is set in their shared state, and reported
back once the parallel workers start.

Some tests are added to show how the failures can happen for btree and
BRIN with a parallel build enforced, which are able to trigger a failure
in an assertion added by 24f520594809 in the recovery TAP test
027_stream_regress.pl where pg_stat_statements is always loaded.  In
this case, the executor path was taken because the index expression
needs to be flattened when building its IndexInfo.

Alexander Lakhin has noticed the problem in btree, and I have noticed
that the issue was more spread.  This is arguably a bug, but nobody has
complained about that until now, so no backpatch is done out of caution.
If folks would like to see a backpatch, well, let me know.

Reported-by: Alexander Lakhin
Reviewed-by: Sami Imseih
Discussion: https://postgr.es/m/cf3547c1-498a-6a61-7b01-819f902a251f@gmail.com

4 files changed, 42 insertions, 0 deletions

diff --git a/src/test/regress/expected/brin.out b/src/test/regress/expected/brin.out
index d6779d8c7d2..e1db2280cf9 100644
--- a/src/test/regress/expected/brin.out
+++ b/src/test/regress/expected/brin.out
@@ -567,6 +567,16 @@ SELECT * FROM brintest_3 WHERE b < '0';
 
 DROP TABLE brintest_3;
 RESET enable_seqscan;
+-- test parallel build with immutable function.
+CREATE TABLE brintest_expr (n int);
+CREATE FUNCTION brintest_func() RETURNS int LANGUAGE sql IMMUTABLE RETURN 0;
+BEGIN;
+SET LOCAL min_parallel_table_scan_size = 0;
+SET LOCAL max_parallel_maintenance_workers = 4;
+CREATE INDEX brintest_expr_idx ON brintest_expr USING brin (brintest_func());
+COMMIT;
+DROP TABLE brintest_expr;
+DROP FUNCTION brintest_func();
 -- test an unlogged table, mostly to get coverage of brinbuildempty
 CREATE UNLOGGED TABLE brintest_unlogged (n numrange);
 CREATE INDEX brinidx_unlogged ON brintest_unlogged USING brin (n);
diff --git a/src/test/regress/expected/btree_index.out b/src/test/regress/expected/btree_index.out
index b350efe128c..d3f4c7e08c3 100644
--- a/src/test/regress/expected/btree_index.out
+++ b/src/test/regress/expected/btree_index.out
@@ -476,6 +476,16 @@ INSERT INTO delete_test_table SELECT i, 1, 2, 3 FROM generate_series(1,1000) i;
 -- Test unsupported btree opclass parameters
 create index on btree_tall_tbl (id int4_ops(foo=1));
 ERROR:  operator class int4_ops has no options
+-- test parallel build with immutable function.
+CREATE TABLE btree_test_expr (n int);
+CREATE FUNCTION btree_test_func() RETURNS int LANGUAGE sql IMMUTABLE RETURN 0;
+BEGIN;
+SET LOCAL min_parallel_table_scan_size = 0;
+SET LOCAL max_parallel_maintenance_workers = 4;
+CREATE INDEX btree_test_expr_idx ON btree_test_expr USING btree (btree_test_func());
+COMMIT;
+DROP TABLE btree_test_expr;
+DROP FUNCTION btree_test_func();
 -- Test case of ALTER INDEX with abuse of column names for indexes.
 -- This grammar is not officially supported, but the parser allows it.
 CREATE INDEX btree_tall_idx2 ON btree_tall_tbl (id);
diff --git a/src/test/regress/sql/brin.sql b/src/test/regress/sql/brin.sql
index 695cfad4bea..7ea97f47c8d 100644
--- a/src/test/regress/sql/brin.sql
+++ b/src/test/regress/sql/brin.sql
@@ -510,6 +510,17 @@ SELECT * FROM brintest_3 WHERE b < '0';
 DROP TABLE brintest_3;
 RESET enable_seqscan;
 
+-- test parallel build with immutable function.
+CREATE TABLE brintest_expr (n int);
+CREATE FUNCTION brintest_func() RETURNS int LANGUAGE sql IMMUTABLE RETURN 0;
+BEGIN;
+SET LOCAL min_parallel_table_scan_size = 0;
+SET LOCAL max_parallel_maintenance_workers = 4;
+CREATE INDEX brintest_expr_idx ON brintest_expr USING brin (brintest_func());
+COMMIT;
+DROP TABLE brintest_expr;
+DROP FUNCTION brintest_func();
+
 -- test an unlogged table, mostly to get coverage of brinbuildempty
 CREATE UNLOGGED TABLE brintest_unlogged (n numrange);
 CREATE INDEX brinidx_unlogged ON brintest_unlogged USING brin (n);
diff --git a/src/test/regress/sql/btree_index.sql b/src/test/regress/sql/btree_index.sql
index 0d2a33f3705..2c3b1352926 100644
--- a/src/test/regress/sql/btree_index.sql
+++ b/src/test/regress/sql/btree_index.sql
@@ -272,6 +272,17 @@ INSERT INTO delete_test_table SELECT i, 1, 2, 3 FROM generate_series(1,1000) i;
 -- Test unsupported btree opclass parameters
 create index on btree_tall_tbl (id int4_ops(foo=1));
 
+-- test parallel build with immutable function.
+CREATE TABLE btree_test_expr (n int);
+CREATE FUNCTION btree_test_func() RETURNS int LANGUAGE sql IMMUTABLE RETURN 0;
+BEGIN;
+SET LOCAL min_parallel_table_scan_size = 0;
+SET LOCAL max_parallel_maintenance_workers = 4;
+CREATE INDEX btree_test_expr_idx ON btree_test_expr USING btree (btree_test_func());
+COMMIT;
+DROP TABLE btree_test_expr;
+DROP FUNCTION btree_test_func();
+
 -- Test case of ALTER INDEX with abuse of column names for indexes.
 -- This grammar is not officially supported, but the parser allows it.
 CREATE INDEX btree_tall_idx2 ON btree_tall_tbl (id);