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Commite690b95

Browse files
committed
Avoid retrieving dummy NULL columns in postgres_fdw.
This should provide some marginal overall savings, since it surely takesmany more cycles for the remote server to deal with the NULL columns thanit takes for postgres_fdw not to emit them. But really the reason is tokeep the emitted queries from looking quite so silly ...
1 parent9cbc4b8 commite690b95

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5 files changed

+301
-218
lines changed

5 files changed

+301
-218
lines changed

‎contrib/postgres_fdw/deparse.c‎

Lines changed: 69 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -106,10 +106,12 @@ static void deparseTargetList(StringInfo buf,
106106
PlannerInfo*root,
107107
Indexrtindex,
108108
Relationrel,
109-
Bitmapset*attrs_used);
109+
Bitmapset*attrs_used,
110+
List**retrieved_attrs);
110111
staticvoiddeparseReturningList(StringInfobuf,PlannerInfo*root,
111112
Indexrtindex,Relationrel,
112-
List*returningList);
113+
List*returningList,
114+
List**retrieved_attrs);
113115
staticvoiddeparseColumnRef(StringInfobuf,intvarno,intvarattno,
114116
PlannerInfo*root);
115117
staticvoiddeparseRelation(StringInfobuf,Relationrel);
@@ -652,12 +654,16 @@ is_builtin(Oid oid)
652654
* Construct a simple SELECT statement that retrieves desired columns
653655
* of the specified foreign table, and append it to "buf".The output
654656
* contains just "SELECT ... FROM tablename".
657+
*
658+
* We also create an integer List of the columns being retrieved, which is
659+
* returned to *retrieved_attrs.
655660
*/
656661
void
657662
deparseSelectSql(StringInfobuf,
658663
PlannerInfo*root,
659664
RelOptInfo*baserel,
660-
Bitmapset*attrs_used)
665+
Bitmapset*attrs_used,
666+
List**retrieved_attrs)
661667
{
662668
RangeTblEntry*rte=planner_rt_fetch(baserel->relid,root);
663669
Relationrel;
@@ -672,7 +678,8 @@ deparseSelectSql(StringInfo buf,
672678
* Construct SELECT list
673679
*/
674680
appendStringInfoString(buf,"SELECT ");
675-
deparseTargetList(buf,root,baserel->relid,rel,attrs_used);
681+
deparseTargetList(buf,root,baserel->relid,rel,attrs_used,
682+
retrieved_attrs);
676683

677684
/*
678685
* Construct FROM clause
@@ -687,24 +694,24 @@ deparseSelectSql(StringInfo buf,
687694
* Emit a target list that retrieves the columns specified in attrs_used.
688695
* This is used for both SELECT and RETURNING targetlists.
689696
*
690-
* We list attributes in order of the foreign table's columns, but replace
691-
* any attributes that need not be fetched with NULL constants. (We can't
692-
* just omit such attributes, or we'll lose track of which columns are
693-
* which at runtime.) Note however that any dropped columns are ignored.
694-
* Also, if ctid needs to be retrieved, it's added at the end.
697+
* The tlist text is appended to buf, and we also create an integer List
698+
* of the columns being retrieved, which is returned to *retrieved_attrs.
695699
*/
696700
staticvoid
697701
deparseTargetList(StringInfobuf,
698702
PlannerInfo*root,
699703
Indexrtindex,
700704
Relationrel,
701-
Bitmapset*attrs_used)
705+
Bitmapset*attrs_used,
706+
List**retrieved_attrs)
702707
{
703708
TupleDesctupdesc=RelationGetDescr(rel);
704709
boolhave_wholerow;
705710
boolfirst;
706711
inti;
707712

713+
*retrieved_attrs=NIL;
714+
708715
/* If there's a whole-row reference, we'll need all the columns. */
709716
have_wholerow=bms_is_member(0-FirstLowInvalidHeapAttributeNumber,
710717
attrs_used);
@@ -718,16 +725,18 @@ deparseTargetList(StringInfo buf,
718725
if (attr->attisdropped)
719726
continue;
720727

721-
if (!first)
722-
appendStringInfoString(buf,", ");
723-
first= false;
724-
725728
if (have_wholerow||
726729
bms_is_member(i-FirstLowInvalidHeapAttributeNumber,
727730
attrs_used))
731+
{
732+
if (!first)
733+
appendStringInfoString(buf,", ");
734+
first= false;
735+
728736
deparseColumnRef(buf,rtindex,i,root);
729-
else
730-
appendStringInfoString(buf,"NULL");
737+
738+
*retrieved_attrs=lappend_int(*retrieved_attrs,i);
739+
}
731740
}
732741

733742
/*
@@ -742,6 +751,9 @@ deparseTargetList(StringInfo buf,
742751
first= false;
743752

744753
appendStringInfoString(buf,"ctid");
754+
755+
*retrieved_attrs=lappend_int(*retrieved_attrs,
756+
SelfItemPointerAttributeNumber);
745757
}
746758

747759
/* Don't generate bad syntax if no undropped columns */
@@ -809,11 +821,16 @@ appendWhereClause(StringInfo buf,
809821

810822
/*
811823
* deparse remote INSERT statement
824+
*
825+
* The statement text is appended to buf, and we also create an integer List
826+
* of the columns being retrieved by RETURNING (if any), which is returned
827+
* to *retrieved_attrs.
812828
*/
813829
void
814830
deparseInsertSql(StringInfobuf,PlannerInfo*root,
815831
Indexrtindex,Relationrel,
816-
List*targetAttrs,List*returningList)
832+
List*targetAttrs,List*returningList,
833+
List**retrieved_attrs)
817834
{
818835
AttrNumberpindex;
819836
boolfirst;
@@ -858,16 +875,24 @@ deparseInsertSql(StringInfo buf, PlannerInfo *root,
858875
appendStringInfoString(buf," DEFAULT VALUES");
859876

860877
if (returningList)
861-
deparseReturningList(buf,root,rtindex,rel,returningList);
878+
deparseReturningList(buf,root,rtindex,rel,returningList,
879+
retrieved_attrs);
880+
else
881+
*retrieved_attrs=NIL;
862882
}
863883

864884
/*
865885
* deparse remote UPDATE statement
886+
*
887+
* The statement text is appended to buf, and we also create an integer List
888+
* of the columns being retrieved by RETURNING (if any), which is returned
889+
* to *retrieved_attrs.
866890
*/
867891
void
868892
deparseUpdateSql(StringInfobuf,PlannerInfo*root,
869893
Indexrtindex,Relationrel,
870-
List*targetAttrs,List*returningList)
894+
List*targetAttrs,List*returningList,
895+
List**retrieved_attrs)
871896
{
872897
AttrNumberpindex;
873898
boolfirst;
@@ -894,23 +919,34 @@ deparseUpdateSql(StringInfo buf, PlannerInfo *root,
894919
appendStringInfoString(buf," WHERE ctid = $1");
895920

896921
if (returningList)
897-
deparseReturningList(buf,root,rtindex,rel,returningList);
922+
deparseReturningList(buf,root,rtindex,rel,returningList,
923+
retrieved_attrs);
924+
else
925+
*retrieved_attrs=NIL;
898926
}
899927

900928
/*
901929
* deparse remote DELETE statement
930+
*
931+
* The statement text is appended to buf, and we also create an integer List
932+
* of the columns being retrieved by RETURNING (if any), which is returned
933+
* to *retrieved_attrs.
902934
*/
903935
void
904936
deparseDeleteSql(StringInfobuf,PlannerInfo*root,
905937
Indexrtindex,Relationrel,
906-
List*returningList)
938+
List*returningList,
939+
List**retrieved_attrs)
907940
{
908941
appendStringInfoString(buf,"DELETE FROM ");
909942
deparseRelation(buf,rel);
910943
appendStringInfoString(buf," WHERE ctid = $1");
911944

912945
if (returningList)
913-
deparseReturningList(buf,root,rtindex,rel,returningList);
946+
deparseReturningList(buf,root,rtindex,rel,returningList,
947+
retrieved_attrs);
948+
else
949+
*retrieved_attrs=NIL;
914950
}
915951

916952
/*
@@ -919,7 +955,8 @@ deparseDeleteSql(StringInfo buf, PlannerInfo *root,
919955
staticvoid
920956
deparseReturningList(StringInfobuf,PlannerInfo*root,
921957
Indexrtindex,Relationrel,
922-
List*returningList)
958+
List*returningList,
959+
List**retrieved_attrs)
923960
{
924961
Bitmapset*attrs_used;
925962

@@ -931,7 +968,8 @@ deparseReturningList(StringInfo buf, PlannerInfo *root,
931968
&attrs_used);
932969

933970
appendStringInfoString(buf," RETURNING ");
934-
deparseTargetList(buf,root,rtindex,rel,attrs_used);
971+
deparseTargetList(buf,root,rtindex,rel,attrs_used,
972+
retrieved_attrs);
935973
}
936974

937975
/*
@@ -959,10 +997,11 @@ deparseAnalyzeSizeSql(StringInfo buf, Relation rel)
959997
/*
960998
* Construct SELECT statement to acquire sample rows of given relation.
961999
*
962-
* Note: command is appended to whatever might be in buf already.
1000+
* SELECT command is appended to buf, and list of columns retrieved
1001+
* is returned to *retrieved_attrs.
9631002
*/
9641003
void
965-
deparseAnalyzeSql(StringInfobuf,Relationrel)
1004+
deparseAnalyzeSql(StringInfobuf,Relationrel,List**retrieved_attrs)
9661005
{
9671006
Oidrelid=RelationGetRelid(rel);
9681007
TupleDesctupdesc=RelationGetDescr(rel);
@@ -972,6 +1011,8 @@ deparseAnalyzeSql(StringInfo buf, Relation rel)
9721011
ListCell*lc;
9731012
boolfirst= true;
9741013

1014+
*retrieved_attrs=NIL;
1015+
9751016
appendStringInfoString(buf,"SELECT ");
9761017
for (i=0;i<tupdesc->natts;i++)
9771018
{
@@ -999,6 +1040,8 @@ deparseAnalyzeSql(StringInfo buf, Relation rel)
9991040
}
10001041

10011042
appendStringInfoString(buf,quote_identifier(colname));
1043+
1044+
*retrieved_attrs=lappend_int(*retrieved_attrs,i+1);
10021045
}
10031046

10041047
/* Don't generate bad syntax for zero-column relation. */

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