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Fix whole-row references in postgres_fdw.
The optimization to not retrieve unnecessary columns wasn't smart enough. Noted by Thom Brown.
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3 files changed

+39
-1
lines changed

3 files changed

+39
-1
lines changed

‎contrib/postgres_fdw/deparse.c

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -364,6 +364,7 @@ deparseSimpleSql(StringInfo buf,
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{
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RangeTblEntry *rte = root->simple_rte_array[baserel->relid];
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Bitmapset *attrs_used = NULL;
367+
bool have_wholerow;
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bool first;
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AttrNumber attr;
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ListCell *lc;
@@ -381,6 +382,10 @@ deparseSimpleSql(StringInfo buf,
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&attrs_used);
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}
383384

385+
/* If there's a whole-row reference, we'll need all the columns. */
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have_wholerow = bms_is_member(0 - FirstLowInvalidHeapAttributeNumber,
387+
attrs_used);
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/*
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* Construct SELECT list
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*
@@ -401,7 +406,8 @@ deparseSimpleSql(StringInfo buf,
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appendStringInfo(buf, ", ");
402407
first = false;
403408

404-
if (bms_is_member(attr - FirstLowInvalidHeapAttributeNumber,
409+
if (have_wholerow ||
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bms_is_member(attr - FirstLowInvalidHeapAttributeNumber,
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attrs_used))
406412
deparseColumnRef(buf, baserel->relid, attr, root);
407413
else

‎contrib/postgres_fdw/expected/postgres_fdw.out

Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -180,6 +180,35 @@ SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
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110 | 0 | 00110 | Sun Jan 11 00:00:00 1970 PST | Sun Jan 11 00:00:00 1970 | 0 | 0 | foo
181181
(10 rows)
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-- whole-row reference
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EXPLAIN (VERBOSE, COSTS false) SELECT t1 FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
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QUERY PLAN
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-------------------------------------------------------------------------------------
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Limit
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Output: t1.*, c3, c1
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-> Sort
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Output: t1.*, c3, c1
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Sort Key: t1.c3, t1.c1
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-> Foreign Scan on public.ft1 t1
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Output: t1.*, c3, c1
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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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(8 rows)
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SELECT t1 FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
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t1
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--------------------------------------------------------------------------------------------
200+
(101,1,00101,"Fri Jan 02 00:00:00 1970 PST","Fri Jan 02 00:00:00 1970",1,"1 ",foo)
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(102,2,00102,"Sat Jan 03 00:00:00 1970 PST","Sat Jan 03 00:00:00 1970",2,"2 ",foo)
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(103,3,00103,"Sun Jan 04 00:00:00 1970 PST","Sun Jan 04 00:00:00 1970",3,"3 ",foo)
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(104,4,00104,"Mon Jan 05 00:00:00 1970 PST","Mon Jan 05 00:00:00 1970",4,"4 ",foo)
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(105,5,00105,"Tue Jan 06 00:00:00 1970 PST","Tue Jan 06 00:00:00 1970",5,"5 ",foo)
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(106,6,00106,"Wed Jan 07 00:00:00 1970 PST","Wed Jan 07 00:00:00 1970",6,"6 ",foo)
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(107,7,00107,"Thu Jan 08 00:00:00 1970 PST","Thu Jan 08 00:00:00 1970",7,"7 ",foo)
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(108,8,00108,"Fri Jan 09 00:00:00 1970 PST","Fri Jan 09 00:00:00 1970",8,"8 ",foo)
208+
(109,9,00109,"Sat Jan 10 00:00:00 1970 PST","Sat Jan 10 00:00:00 1970",9,"9 ",foo)
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(110,0,00110,"Sun Jan 11 00:00:00 1970 PST","Sun Jan 11 00:00:00 1970",0,"0 ",foo)
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(10 rows)
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-- empty result
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SELECT * FROM ft1 WHERE false;
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c1 | c2 | c3 | c4 | c5 | c6 | c7 | c8

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -136,6 +136,9 @@ EXPLAIN (COSTS false) SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
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SELECT * FROM ft1 ORDER BY c3, c1 OFFSET 100 LIMIT 10;
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EXPLAIN (VERBOSE, COSTS false) SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
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SELECT * FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
139+
-- whole-row reference
140+
EXPLAIN (VERBOSE, COSTS false) SELECT t1 FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
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SELECT t1 FROM ft1 t1 ORDER BY t1.c3, t1.c1 OFFSET 100 LIMIT 10;
139142
-- empty result
140143
SELECT * FROM ft1 WHERE false;
141144
-- with WHERE clause

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