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Commitda7d44b

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postgres_fdw: Clean up handling of system columns.
Previously, querying the xmin column of a single postgres_fdw foreigntable fetched the tuple length, xmax the typmod, and cmin or cmax thecomposite type OID of the tuple. However, when you queried severalsuch tables and the join got shipped to the remote side, these columnsended up containing the remote values of the corresponding columns.Both behaviors are rather unprincipled, the former for obvious reasonsand the latter because the remote values of these columns don't haveany local significance; our transaction IDs are in a different spacethan those of the remote machine. Clean this up by setting all ofthese fields to 0 in both cases. Also fix the handling of tableoidto be sane.Robert Haas and Ashutosh Bapat, reviewed by Etsuro Fujita.
1 parent5702277 commitda7d44b

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3 files changed

+78
-22
lines changed

3 files changed

+78
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lines changed

‎contrib/postgres_fdw/deparse.c

Lines changed: 45 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1571,13 +1571,38 @@ deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
15711571
{
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RangeTblEntry*rte;
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1574-
/* varattno can be a whole-row reference, ctid or a regular table column */
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if (varattno==SelfItemPointerAttributeNumber)
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{
1576+
/* We support fetching the remote side's CTID. */
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if (qualify_col)
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ADD_REL_QUALIFIER(buf,varno);
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appendStringInfoString(buf,"ctid");
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}
1581+
elseif (varattno<0)
1582+
{
1583+
/*
1584+
* All other system attributes are fetched as 0, except for table OID,
1585+
* which is fetched as the local table OID. However, we must be
1586+
* careful; the table could be beneath an outer join, in which case
1587+
* it must go to NULL whenever the rest of the row does.
1588+
*/
1589+
Oidfetchval=0;
1590+
1591+
if (varattno==TableOidAttributeNumber)
1592+
{
1593+
rte=planner_rt_fetch(varno,root);
1594+
fetchval=rte->relid;
1595+
}
1596+
1597+
if (qualify_col)
1598+
{
1599+
appendStringInfoString(buf,"CASE WHEN ");
1600+
ADD_REL_QUALIFIER(buf,varno);
1601+
appendStringInfo(buf,"* IS NOT NULL THEN %u END",fetchval);
1602+
}
1603+
else
1604+
appendStringInfo(buf,"%u",fetchval);
1605+
}
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elseif (varattno==0)
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{
15831608
/* Whole row reference */
@@ -1606,10 +1631,29 @@ deparseColumnRef(StringInfo buf, int varno, int varattno, PlannerInfo *root,
16061631
*/
16071632
attrs_used=bms_add_member(NULL,
16081633
0-FirstLowInvalidHeapAttributeNumber);
1634+
1635+
/*
1636+
* In case the whole-row reference is under an outer join then it has to
1637+
* go NULL whenver the rest of the row goes NULL. Deparsing a join query
1638+
* would always involve multiple relations, thus qualify_col would be
1639+
* true.
1640+
*/
1641+
if (qualify_col)
1642+
{
1643+
appendStringInfoString(buf,"CASE WHEN ");
1644+
ADD_REL_QUALIFIER(buf,varno);
1645+
appendStringInfo(buf,"* IS NOT NULL THEN ");
1646+
}
1647+
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appendStringInfoString(buf,"ROW(");
16101649
deparseTargetList(buf,root,varno,rel, false,attrs_used,qualify_col,
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&retrieved_attrs);
16121651
appendStringInfoString(buf,")");
1652+
1653+
/* Complete the CASE WHEN statement started above. */
1654+
if (qualify_col)
1655+
appendStringInfo(buf," END");
1656+
16131657
heap_close(rel,NoLock);
16141658
bms_free(attrs_used);
16151659
}

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