From c399248b3b44bd6cece1ada47eee346b67a88a0a Mon Sep 17 00:00:00 2001 From: David Rowley Date: Mon, 11 Mar 2024 12:27:11 +1300 Subject: [PATCH] Fix deparsing of Consts in postgres_fdw ORDER BY MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit For UNION ALL queries where a union child query contained a foreign table, if the targetlist of that query contained a constant, and the top-level query performed an ORDER BY which contained the column for the constant value, then postgres_fdw would find the EquivalenceMember with the Const and then try to produce an ORDER BY containing that Const. This caused problems with INT typed Consts as these could appear to be requests to order by an ordinal column position rather than the constant value. This could lead to either an error such as: ERROR: ORDER BY position is not in select list or worse, if the constant value is a valid column, then we could just sort by the wrong column altogether. Here we fix this issue by just not including these Consts in the ORDER BY clause. In passing, add a new section for testing ORDER BY in the postgres_fdw tests and move two existing tests which were misplaced in the WHERE clause testing section into it. Reported-by: Michał Kłeczek Reviewed-by: Ashutosh Bapat, Richard Guo Bug: #18381 Discussion: https://postgr.es/m/0714C8B8-8D82-4ABB-9F8D-A0C3657E7B6E%40kleczek.org Discussion: https://postgr.es/m/18381-137456acd168bf93%40postgresql.org Backpatch-through: 12, oldest supported version --- contrib/postgres_fdw/deparse.c | 25 ++++- .../postgres_fdw/expected/postgres_fdw.out | 93 +++++++++++++------ contrib/postgres_fdw/sql/postgres_fdw.sql | 32 +++++-- 3 files changed, 114 insertions(+), 36 deletions(-) diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c index 8fc66fa11c..8787c00d3e 100644 --- a/contrib/postgres_fdw/deparse.c +++ b/contrib/postgres_fdw/deparse.c @@ -3912,13 +3912,12 @@ appendOrderByClause(List *pathkeys, bool has_final_sort, { ListCell *lcell; int nestlevel; - const char *delim = " "; StringInfo buf = context->buf; + bool gotone = false; /* Make sure any constants in the exprs are printed portably */ nestlevel = set_transmission_modes(); - appendStringInfoString(buf, " ORDER BY"); foreach(lcell, pathkeys) { PathKey *pathkey = lfirst(lcell); @@ -3951,6 +3950,26 @@ appendOrderByClause(List *pathkeys, bool has_final_sort, em_expr = em->em_expr; + /* + * If the member is a Const expression then we needn't add it to the + * ORDER BY clause. This can happen in UNION ALL queries where the + * union child targetlist has a Const. Adding these would be + * wasteful, but also, for INT columns, an integer literal would be + * seen as an ordinal column position rather than a value to sort by. + * deparseConst() does have code to handle this, but it seems less + * effort on all accounts just to skip these for ORDER BY clauses. + */ + if (IsA(em_expr, Const)) + continue; + + if (!gotone) + { + appendStringInfoString(buf, " ORDER BY "); + gotone = true; + } + else + appendStringInfoString(buf, ", "); + /* * Lookup the operator corresponding to the strategy in the opclass. * The datatype used by the opfamily is not necessarily the same as @@ -3965,7 +3984,6 @@ appendOrderByClause(List *pathkeys, bool has_final_sort, pathkey->pk_strategy, em->em_datatype, em->em_datatype, pathkey->pk_opfamily); - appendStringInfoString(buf, delim); deparseExpr(em_expr, context); /* @@ -3975,7 +3993,6 @@ appendOrderByClause(List *pathkeys, bool has_final_sort, appendOrderBySuffix(oprid, exprType((Node *) em_expr), pathkey->pk_nulls_first, context); - delim = ", "; } reset_transmission_modes(nestlevel); } diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index c355e8f3f7..58a603ac56 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -893,32 +893,6 @@ SELECT * FROM ft2 WHERE c1 = ANY (ARRAY(SELECT c1 FROM ft1 WHERE c1 < 5)); 4 | 4 | 00004 | Mon Jan 05 00:00:00 1970 PST | Mon Jan 05 00:00:00 1970 | 4 | 4 | foo (4 rows) --- we should not push order by clause with volatile expressions or unsafe --- collations -EXPLAIN (VERBOSE, COSTS OFF) - SELECT * FROM ft2 ORDER BY ft2.c1, random(); - QUERY PLAN -------------------------------------------------------------------------------- - Sort - Output: c1, c2, c3, c4, c5, c6, c7, c8, (random()) - Sort Key: ft2.c1, (random()) - -> Foreign Scan on public.ft2 - Output: c1, c2, c3, c4, c5, c6, c7, c8, random() - Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" -(6 rows) - -EXPLAIN (VERBOSE, COSTS OFF) - SELECT * FROM ft2 ORDER BY ft2.c1, ft2.c3 collate "C"; - QUERY PLAN -------------------------------------------------------------------------------- - Sort - Output: c1, c2, c3, c4, c5, c6, c7, c8, ((c3)::text) - Sort Key: ft2.c1, ft2.c3 COLLATE "C" - -> Foreign Scan on public.ft2 - Output: c1, c2, c3, c4, c5, c6, c7, c8, c3 - Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" -(6 rows) - -- user-defined operator/function CREATE FUNCTION postgres_fdw_abs(int) RETURNS int AS $$ BEGIN @@ -1206,6 +1180,73 @@ WHERE c1 = 642 AND length(to_tsvector('custom_search'::regconfig, c3)) > 0; 642 | '00642':1 (1 row) +-- =================================================================== +-- ORDER BY queries +-- =================================================================== +-- we should not push order by clause with volatile expressions or unsafe +-- collations +EXPLAIN (VERBOSE, COSTS OFF) + SELECT * FROM ft2 ORDER BY ft2.c1, random(); + QUERY PLAN +------------------------------------------------------------------------------- + Sort + Output: c1, c2, c3, c4, c5, c6, c7, c8, (random()) + Sort Key: ft2.c1, (random()) + -> Foreign Scan on public.ft2 + Output: c1, c2, c3, c4, c5, c6, c7, c8, random() + Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" +(6 rows) + +EXPLAIN (VERBOSE, COSTS OFF) + SELECT * FROM ft2 ORDER BY ft2.c1, ft2.c3 collate "C"; + QUERY PLAN +------------------------------------------------------------------------------- + Sort + Output: c1, c2, c3, c4, c5, c6, c7, c8, ((c3)::text) + Sort Key: ft2.c1, ft2.c3 COLLATE "C" + -> Foreign Scan on public.ft2 + Output: c1, c2, c3, c4, c5, c6, c7, c8, c3 + Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" +(6 rows) + +-- Ensure we don't push ORDER BY expressions which are Consts at the UNION +-- child level to the foreign server. +EXPLAIN (VERBOSE, COSTS OFF) +SELECT * FROM ( + SELECT 1 AS type,c1 FROM ft1 + UNION ALL + SELECT 2 AS type,c1 FROM ft2 +) a ORDER BY type,c1; + QUERY PLAN +--------------------------------------------------------------------------------- + Merge Append + Sort Key: (1), ft1.c1 + -> Foreign Scan on public.ft1 + Output: 1, ft1.c1 + Remote SQL: SELECT "C 1" FROM "S 1"."T 1" ORDER BY "C 1" ASC NULLS LAST + -> Foreign Scan on public.ft2 + Output: 2, ft2.c1 + Remote SQL: SELECT "C 1" FROM "S 1"."T 1" ORDER BY "C 1" ASC NULLS LAST +(8 rows) + +EXPLAIN (VERBOSE, COSTS OFF) +SELECT * FROM ( + SELECT 1 AS type,c1 FROM ft1 + UNION ALL + SELECT 2 AS type,c1 FROM ft2 +) a ORDER BY type; + QUERY PLAN +--------------------------------------------------- + Merge Append + Sort Key: (1) + -> Foreign Scan on public.ft1 + Output: 1, ft1.c1 + Remote SQL: SELECT "C 1" FROM "S 1"."T 1" + -> Foreign Scan on public.ft2 + Output: 2, ft2.c1 + Remote SQL: SELECT "C 1" FROM "S 1"."T 1" +(8 rows) + -- =================================================================== -- JOIN queries -- =================================================================== diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 812e7646e1..e3d147de6d 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -355,12 +355,6 @@ WHERE a.c2 = 6 AND b.c1 = a.c1 AND a.c8 = 'foo' AND b.c7 = upper(a.c7); -- bug before 9.3.5 due to sloppy handling of remote-estimate parameters SELECT * FROM ft1 WHERE c1 = ANY (ARRAY(SELECT c1 FROM ft2 WHERE c1 < 5)); SELECT * FROM ft2 WHERE c1 = ANY (ARRAY(SELECT c1 FROM ft1 WHERE c1 < 5)); --- we should not push order by clause with volatile expressions or unsafe --- collations -EXPLAIN (VERBOSE, COSTS OFF) - SELECT * FROM ft2 ORDER BY ft2.c1, random(); -EXPLAIN (VERBOSE, COSTS OFF) - SELECT * FROM ft2 ORDER BY ft2.c1, ft2.c3 collate "C"; -- user-defined operator/function CREATE FUNCTION postgres_fdw_abs(int) RETURNS int AS $$ @@ -462,6 +456,32 @@ WHERE c1 = 642 AND length(to_tsvector('custom_search'::regconfig, c3)) > 0; SELECT c1, to_tsvector('custom_search'::regconfig, c3) FROM ft1 WHERE c1 = 642 AND length(to_tsvector('custom_search'::regconfig, c3)) > 0; +-- =================================================================== +-- ORDER BY queries +-- =================================================================== +-- we should not push order by clause with volatile expressions or unsafe +-- collations +EXPLAIN (VERBOSE, COSTS OFF) + SELECT * FROM ft2 ORDER BY ft2.c1, random(); +EXPLAIN (VERBOSE, COSTS OFF) + SELECT * FROM ft2 ORDER BY ft2.c1, ft2.c3 collate "C"; + +-- Ensure we don't push ORDER BY expressions which are Consts at the UNION +-- child level to the foreign server. +EXPLAIN (VERBOSE, COSTS OFF) +SELECT * FROM ( + SELECT 1 AS type,c1 FROM ft1 + UNION ALL + SELECT 2 AS type,c1 FROM ft2 +) a ORDER BY type,c1; + +EXPLAIN (VERBOSE, COSTS OFF) +SELECT * FROM ( + SELECT 1 AS type,c1 FROM ft1 + UNION ALL + SELECT 2 AS type,c1 FROM ft2 +) a ORDER BY type; + -- =================================================================== -- JOIN queries -- ===================================================================