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Commit9c58101

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Fix mishandling of system columns in FDW queries.
postgres_fdw would send query conditions involving system columns to theremote server, even though it makes no effort to ensure that systemcolumns other than CTID match what the remote side thinks. tableoid,in particular, probably won't match and might have some use in queries.Hence, prevent sending conditions that include non-CTID system columns.Also, create_foreignscan_plan neglected to check local restrictionconditions while determining whether to set fsSystemCol for a foreignscan plan node. This again would bollix the results for queries thattest a foreign table's tableoid.Back-patch the first fix to 9.3 where postgres_fdw was introduced.Back-patch the second to 9.2. The code is probably broken in 9.1 aswell, but the patch doesn't apply cleanly there; given the weak stateof support for FDWs in 9.1, it doesn't seem worth fixing.Etsuro Fujita, reviewed by Ashutosh Bapat, and somewhat modified by me
1 parenteca2b9b commit9c58101

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4 files changed

+116
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lines changed

4 files changed

+116
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lines changed

‎contrib/postgres_fdw/deparse.c

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -254,6 +254,18 @@ foreign_expr_walker(Node *node,
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var->varlevelsup==0)
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{
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/* Var belongs to foreign table */
257+
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/*
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* System columns other than ctid should not be sent to
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* the remote, since we don't make any effort to ensure
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* that local and remote values match (tableoid, in
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* particular, almost certainly doesn't match).
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*/
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if (var->varattno<0&&
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var->varattno!=SelfItemPointerAttributeNumber)
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return false;
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/* Else check the collation */
257269
collation=var->varcollid;
258270
state=OidIsValid(collation) ?FDW_COLLATE_SAFE :FDW_COLLATE_NONE;
259271
}

‎contrib/postgres_fdw/expected/postgres_fdw.out

Lines changed: 68 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -832,6 +832,74 @@ DEALLOCATE st2;
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DEALLOCATE st3;
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DEALLOCATE st4;
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DEALLOCATE st5;
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-- System columns, except ctid, should not be sent to remote
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EXPLAIN (VERBOSE, COSTS false)
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SELECT * FROM ft1 t1 WHERE t1.tableoid = 'pg_class'::regclass LIMIT 1;
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QUERY PLAN
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-------------------------------------------------------------------------------
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Limit
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Output: c1, c2, c3, c4, c5, c6, c7, c8
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-> Foreign Scan on public.ft1 t1
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Output: c1, c2, c3, c4, c5, c6, c7, c8
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Filter: (t1.tableoid = 1259::oid)
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Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
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(6 rows)
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SELECT * FROM ft1 t1 WHERE t1.tableoid = 'ft1'::regclass LIMIT 1;
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c1 | c2 | c3 | c4 | c5 | c6 | c7 | c8
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----+----+-------+------------------------------+--------------------------+----+------------+-----
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1 | 1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1 | 1 | foo
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(1 row)
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EXPLAIN (VERBOSE, COSTS false)
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SELECT tableoid::regclass, * FROM ft1 t1 LIMIT 1;
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QUERY PLAN
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-------------------------------------------------------------------------------
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Limit
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Output: ((tableoid)::regclass), c1, c2, c3, c4, c5, c6, c7, c8
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-> Foreign Scan on public.ft1 t1
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Output: (tableoid)::regclass, c1, c2, c3, c4, c5, c6, c7, c8
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Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
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(5 rows)
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865+
SELECT tableoid::regclass, * FROM ft1 t1 LIMIT 1;
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tableoid | c1 | c2 | c3 | c4 | c5 | c6 | c7 | c8
867+
----------+----+----+-------+------------------------------+--------------------------+----+------------+-----
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ft1 | 1 | 1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1 | 1 | foo
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(1 row)
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EXPLAIN (VERBOSE, COSTS false)
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SELECT * FROM ft1 t1 WHERE t1.ctid = '(0,2)';
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QUERY PLAN
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-------------------------------------------------------------------------------------------------------
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Foreign Scan on public.ft1 t1
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Output: c1, c2, c3, c4, c5, c6, c7, c8
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Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE ((ctid = '(0,2)'::tid))
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(3 rows)
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SELECT * FROM ft1 t1 WHERE t1.ctid = '(0,2)';
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c1 | c2 | c3 | c4 | c5 | c6 | c7 | c8
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----+----+-------+------------------------------+--------------------------+----+------------+-----
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2 | 2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2 | 2 | foo
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(1 row)
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EXPLAIN (VERBOSE, COSTS false)
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SELECT ctid, * FROM ft1 t1 LIMIT 1;
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QUERY PLAN
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-------------------------------------------------------------------------------------
890+
Limit
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Output: ctid, c1, c2, c3, c4, c5, c6, c7, c8
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-> Foreign Scan on public.ft1 t1
893+
Output: ctid, c1, c2, c3, c4, c5, c6, c7, c8
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Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8, ctid FROM "S 1"."T 1"
895+
(5 rows)
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SELECT ctid, * FROM ft1 t1 LIMIT 1;
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ctid | c1 | c2 | c3 | c4 | c5 | c6 | c7 | c8
899+
-------+----+----+-------+------------------------------+--------------------------+----+------------+-----
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(0,1) | 1 | 1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1 | 1 | foo
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(1 row)
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835903
-- ===================================================================
836904
-- used in pl/pgsql function
837905
-- ===================================================================

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -254,6 +254,20 @@ DEALLOCATE st3;
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DEALLOCATE st4;
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DEALLOCATE st5;
256256

257+
-- System columns, except ctid, should not be sent to remote
258+
EXPLAIN (VERBOSE, COSTS false)
259+
SELECT*FROM ft1 t1WHEREt1.tableoid='pg_class'::regclassLIMIT1;
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SELECT*FROM ft1 t1WHEREt1.tableoid='ft1'::regclassLIMIT1;
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EXPLAIN (VERBOSE, COSTS false)
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SELECT tableoid::regclass,*FROM ft1 t1LIMIT1;
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SELECT tableoid::regclass,*FROM ft1 t1LIMIT1;
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EXPLAIN (VERBOSE, COSTS false)
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SELECT*FROM ft1 t1WHEREt1.ctid='(0,2)';
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SELECT*FROM ft1 t1WHEREt1.ctid='(0,2)';
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EXPLAIN (VERBOSE, COSTS false)
268+
SELECT ctid,*FROM ft1 t1LIMIT1;
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SELECT ctid,*FROM ft1 t1LIMIT1;
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257271
-- ===================================================================
258272
-- used in pl/pgsql function
259273
-- ===================================================================

‎src/backend/optimizer/plan/createplan.c

Lines changed: 22 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -20,6 +20,7 @@
2020
#include<math.h>
2121

2222
#include"access/skey.h"
23+
#include"access/sysattr.h"
2324
#include"catalog/pg_class.h"
2425
#include"foreign/fdwapi.h"
2526
#include"miscadmin.h"
@@ -1957,6 +1958,8 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
19571958
RelOptInfo*rel=best_path->path.parent;
19581959
Indexscan_relid=rel->relid;
19591960
RangeTblEntry*rte;
1961+
Bitmapset*attrs_used=NULL;
1962+
ListCell*lc;
19601963
inti;
19611964

19621965
/* it should be a base rel... */
@@ -2004,17 +2007,34 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
20042007
* Detect whether any system columns are requested from rel. This is a
20052008
* bit of a kluge and might go away someday, so we intentionally leave it
20062009
* out of the API presented to FDWs.
2010+
*
2011+
* First, examine all the attributes needed for joins or final output.
2012+
* Note: we must look at reltargetlist, not the attr_needed data, because
2013+
* attr_needed isn't computed for inheritance child rels.
20072014
*/
2015+
pull_varattnos((Node*)rel->reltargetlist,rel->relid,&attrs_used);
2016+
2017+
/* Add all the attributes used by restriction clauses. */
2018+
foreach(lc,rel->baserestrictinfo)
2019+
{
2020+
RestrictInfo*rinfo= (RestrictInfo*)lfirst(lc);
2021+
2022+
pull_varattnos((Node*)rinfo->clause,rel->relid,&attrs_used);
2023+
}
2024+
2025+
/* Now, are any system columns requested from rel? */
20082026
scan_plan->fsSystemCol= false;
2009-
for (i=rel->min_attr;i<0;i++)
2027+
for (i=FirstLowInvalidHeapAttributeNumber+1;i<0;i++)
20102028
{
2011-
if (!bms_is_empty(rel->attr_needed[i-rel->min_attr]))
2029+
if (bms_is_member(i-FirstLowInvalidHeapAttributeNumber,attrs_used))
20122030
{
20132031
scan_plan->fsSystemCol= true;
20142032
break;
20152033
}
20162034
}
20172035

2036+
bms_free(attrs_used);
2037+
20182038
returnscan_plan;
20192039
}
20202040

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