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Include result relation info in direct modify ForeignScan nodes.

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FDWs that can perform an UPDATE/DELETE remotely using the "direct modify"
set of APIs need to access the ResultRelInfo of the target table. That's
currently available in EState.es_result_relation_info, but the next
commit will remove that field.

This commit adds a new resultRelation field in ForeignScan, to store the
target relation's RT index, and the corresponding ResultRelInfo in
ForeignScanState. The FDW's PlanDirectModify callback is expected to set
'resultRelation' along with 'operation'. The core code doesn't need them
for anything, they are for the convenience of FDW's Begin- and
IterateDirectModify callbacks.

Authors: Amit Langote, Etsuro Fujita
Discussion: https://www.postgresql.org/message-id/CA%2BHiwqGEmiib8FLiHMhKB%2BCH5dRgHSLc5N5wnvc4kym%2BZYpQEQ%40mail.gmail.com
This commit is contained in:
Heikki Linnakangas
2020-10-14 10:58:38 +03:00
parent 39b4a95100
commit 178f2d560d
10 changed files with 45 additions and 13 deletions
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15
doc/src/sgml/fdwhandler.sgml
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@ -861,11 +861,15 @@ PlanDirectModify(PlannerInfo *root,
To execute the direct modification on the remote server, this function
must rewrite the target subplan with a <structname>ForeignScan</structname> plan
node that executes the direct modification on the remote server. The
<structfield>operation</structfield> field of the <structname>ForeignScan</structname> must
be set to the <literal>CmdType</literal> enumeration appropriately; that is,
<structfield>operation</structfield> and <structfield>resultRelation</structfield> fields
of the <structname>ForeignScan</structname> must be set appropriately.
<structfield>operation</structfield> must be set to the <literal>CmdType</literal>
enumeration corresponding to the statement kind (that is,
<literal>CMD_UPDATE</literal> for <command>UPDATE</command>,
<literal>CMD_INSERT</literal> for <command>INSERT</command>, and
<literal>CMD_DELETE</literal> for <command>DELETE</command>.
<literal>CMD_DELETE</literal> for <command>DELETE</command>), and the
<literal>resultRelation</literal> argument must be copied to the
<structfield>resultRelation</structfield> field.
</para>
<para>
@ -925,9 +929,8 @@ IterateDirectModify(ForeignScanState *node);
needed for the <literal>RETURNING</literal> calculation, returning it in a
tuple table slot (the node's <structfield>ScanTupleSlot</structfield> should be
used for this purpose). The data that was actually inserted, updated
or deleted must be stored in the
<literal>es_result_relation_info-&gt;ri_projectReturning-&gt;pi_exprContext-&gt;ecxt_scantuple</literal>
of the node's <structname>EState</structname>.
or deleted must be stored in
<literal>node->resultRelInfo->ri_projectReturning-&gt;pi_exprContext-&gt;ecxt_scantuple</literal>.
Return NULL if no more rows are available.
Note that this is called in a short-lived memory context that will be
reset between invocations. Create a memory context in