Fix mishandling of system columns in FDW queries.

postgres_fdw would send query conditions involving system columns to the
remote server, even though it makes no effort to ensure that system
columns 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 restriction
conditions while determining whether to set fsSystemCol for a foreign
scan plan node.  This again would bollix the results for queries that
test 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 as
well, but the patch doesn't apply cleanly there; given the weak state
of support for FDWs in 9.1, it doesn't seem worth fixing.

Etsuro Fujita, reviewed by Ashutosh Bapat, and somewhat modified by me

diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index 47cf99e1e009de8679ee8265f47297ea8173756e..a748b7afea19ef0eb1eb01c94de08a8ee0542559 100644 (file)
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -253,6 +253,18 @@ foreign_expr_walker(Node *node,
                    var->varlevelsup == 0)
                {
                    /* Var belongs to foreign table */
+
+                   /*
+                    * System columns other than ctid should not be sent to
+                    * the remote, since we don't make any effort to ensure
+                    * that local and remote values match (tableoid, in
+                    * particular, almost certainly doesn't match).
+                    */
+                   if (var->varattno < 0 &&
+                       var->varattno != SelfItemPointerAttributeNumber)
+                       return false;
+
+                   /* Else check the collation */
                    collation = var->varcollid;
                    state = OidIsValid(collation) ? FDW_COLLATE_SAFE : FDW_COLLATE_NONE;
                }

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index b6b05579e5faea0364b8423b4a7102bf8aefeb26..b17050677a3a8099ff1bff12df60ebf447571f5f 100644 (file)
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -826,6 +826,74 @@ DEALLOCATE st2;
 DEALLOCATE st3;
 DEALLOCATE st4;
 DEALLOCATE st5;
+-- System columns, except ctid, should not be sent to remote
+EXPLAIN (VERBOSE, COSTS false)
+SELECT * FROM ft1 t1 WHERE t1.tableoid = 'pg_class'::regclass LIMIT 1;
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Limit
+   Output: c1, c2, c3, c4, c5, c6, c7, c8
+   ->  Foreign Scan on public.ft1 t1
+         Output: c1, c2, c3, c4, c5, c6, c7, c8
+         Filter: (t1.tableoid = 1259::oid)
+         Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
+(6 rows)
+
+SELECT * FROM ft1 t1 WHERE t1.tableoid = 'ft1'::regclass LIMIT 1;
+ c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     | c8  
+----+----+-------+------------------------------+--------------------------+----+------------+-----
+  1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1          | foo
+(1 row)
+
+EXPLAIN (VERBOSE, COSTS false)
+SELECT tableoid::regclass, * FROM ft1 t1 LIMIT 1;
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Limit
+   Output: ((tableoid)::regclass), c1, c2, c3, c4, c5, c6, c7, c8
+   ->  Foreign Scan on public.ft1 t1
+         Output: (tableoid)::regclass, c1, c2, c3, c4, c5, c6, c7, c8
+         Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
+(5 rows)
+
+SELECT tableoid::regclass, * FROM ft1 t1 LIMIT 1;
+ tableoid | c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     | c8  
+----------+----+----+-------+------------------------------+--------------------------+----+------------+-----
+ ft1      |  1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1          | foo
+(1 row)
+
+EXPLAIN (VERBOSE, COSTS false)
+SELECT * FROM ft1 t1 WHERE t1.ctid = '(0,2)';
+                                              QUERY PLAN                                               
+-------------------------------------------------------------------------------------------------------
+ Foreign Scan on public.ft1 t1
+   Output: c1, c2, c3, c4, c5, c6, c7, c8
+   Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" WHERE ((ctid = '(0,2)'::tid))
+(3 rows)
+
+SELECT * FROM ft1 t1 WHERE t1.ctid = '(0,2)';
+ c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     | c8  
+----+----+-------+------------------------------+--------------------------+----+------------+-----
+  2 |  2 | 00002 | Sat Jan 03 00:00:00 1970 PST | Sat Jan 03 00:00:00 1970 | 2  | 2          | foo
+(1 row)
+
+EXPLAIN (VERBOSE, COSTS false)
+SELECT ctid, * FROM ft1 t1 LIMIT 1;
+                                     QUERY PLAN                                      
+-------------------------------------------------------------------------------------
+ Limit
+   Output: ctid, c1, c2, c3, c4, c5, c6, c7, c8
+   ->  Foreign Scan on public.ft1 t1
+         Output: ctid, c1, c2, c3, c4, c5, c6, c7, c8
+         Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8, ctid FROM "S 1"."T 1"
+(5 rows)
+
+SELECT ctid, * FROM ft1 t1 LIMIT 1;
+ ctid  | c1 | c2 |  c3   |              c4              |            c5            | c6 |     c7     | c8  
+-------+----+----+-------+------------------------------+--------------------------+----+------------+-----
+ (0,1) |  1 |  1 | 00001 | Fri Jan 02 00:00:00 1970 PST | Fri Jan 02 00:00:00 1970 | 1  | 1          | foo
+(1 row)
+
 -- ===================================================================
 -- used in pl/pgsql function
 -- ===================================================================

diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 7ab3f74f3372ae3cf9509768ea627af5c2be079a..d3fda68ff948c208feb009edcda8b15c4aaf28ad 100644 (file)
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -248,6 +248,20 @@ DEALLOCATE st3;
 DEALLOCATE st4;
 DEALLOCATE st5;
 
+-- System columns, except ctid, should not be sent to remote
+EXPLAIN (VERBOSE, COSTS false)
+SELECT * FROM ft1 t1 WHERE t1.tableoid = 'pg_class'::regclass LIMIT 1;
+SELECT * FROM ft1 t1 WHERE t1.tableoid = 'ft1'::regclass LIMIT 1;
+EXPLAIN (VERBOSE, COSTS false)
+SELECT tableoid::regclass, * FROM ft1 t1 LIMIT 1;
+SELECT tableoid::regclass, * FROM ft1 t1 LIMIT 1;
+EXPLAIN (VERBOSE, COSTS false)
+SELECT * FROM ft1 t1 WHERE t1.ctid = '(0,2)';
+SELECT * FROM ft1 t1 WHERE t1.ctid = '(0,2)';
+EXPLAIN (VERBOSE, COSTS false)
+SELECT ctid, * FROM ft1 t1 LIMIT 1;
+SELECT ctid, * FROM ft1 t1 LIMIT 1;
+
 -- ===================================================================
 -- used in pl/pgsql function
 -- ===================================================================

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 3a54cb14652806400e2c304acbd75087ffca69dd..48b87a0f112e0b72961f453e3a76bf36e08fbf3b 100644 (file)
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -20,6 +20,7 @@
 #include 
 
 #include "access/skey.h"
+#include "access/sysattr.h"
 #include "catalog/pg_class.h"
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
@@ -1954,6 +1955,8 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
    RelOptInfo *rel = best_path->path.parent;
    Index       scan_relid = rel->relid;
    RangeTblEntry *rte;
+   Bitmapset  *attrs_used = NULL;
+   ListCell   *lc;
    int         i;
 
    /* it should be a base rel... */
@@ -2001,17 +2004,34 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
     * Detect whether any system columns are requested from rel.  This is a
     * bit of a kluge and might go away someday, so we intentionally leave it
     * out of the API presented to FDWs.
+    *
+    * First, examine all the attributes needed for joins or final output.
+    * Note: we must look at reltargetlist, not the attr_needed data, because
+    * attr_needed isn't computed for inheritance child rels.
     */
+   pull_varattnos((Node *) rel->reltargetlist, rel->relid, &attrs_used);
+
+   /* Add all the attributes used by restriction clauses. */
+   foreach(lc, rel->baserestrictinfo)
+   {
+       RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
+
+       pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
+   }
+
+   /* Now, are any system columns requested from rel? */
    scan_plan->fsSystemCol = false;
-   for (i = rel->min_attr; i < 0; i++)
+   for (i = FirstLowInvalidHeapAttributeNumber + 1; i < 0; i++)
    {
-       if (!bms_is_empty(rel->attr_needed[i - rel->min_attr]))
+       if (bms_is_member(i - FirstLowInvalidHeapAttributeNumber, attrs_used))
        {
            scan_plan->fsSystemCol = true;
            break;
        }
    }
 
+   bms_free(attrs_used);
+
    return scan_plan;
 }