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Expand comments and add an assertion in nodeModifyTable.c.

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Most comments concern RELKIND_VIEW.  One addresses the ExecUpdate()
"tupleid" parameter.  A later commit will rely on these facts, but they
hold already.  Back-patch to v12 (all supported versions), the plan for
that commit.

Reviewed (in an earlier version) by Robert Haas.

Discussion: https://postgr.es/m/20240512232923.aa.nmisch@google.com
This commit is contained in:
Noah Misch 2024-06-27 19:21:05 -07:00
parent 65aae93c45
commit c3437fb725
1 changed files with 17 additions and 7 deletions
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24
src/backend/executor/nodeModifyTable.c
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@ -28,6 +28,14 @@
* rowtype, but we might still find that different plans are appropriate
* for different child relations.
*
* The relation to modify can be an ordinary table, a view having an
* INSTEAD OF trigger, or a foreign table. Earlier processing already
* pointed ModifyTable to the underlying relations of any automatically
* updatable view not using an INSTEAD OF trigger, so code here can
* assume it won't have one as a modification target. This node does
* process ri_WithCheckOptions, which may have expressions from those
* automatically updatable views.
*
* If the query specifies RETURNING, then the ModifyTable returns a
* RETURNING tuple after completing each row insert, update, or delete.
* It must be called again to continue the operation. Without RETURNING,
@ -812,8 +820,8 @@ ExecInsert(ModifyTableState *mtstate,
* index modifications are needed.
*
* When deleting from a table, tupleid identifies the tuple to
* delete and oldtuple is NULL. When deleting from a view,
* oldtuple is passed to the INSTEAD OF triggers and identifies
* delete and oldtuple is NULL. When deleting through a view
* INSTEAD OF trigger, oldtuple is passed to the triggers and identifies
* what to delete, and tupleid is invalid. When deleting from a
* foreign table, tupleid is invalid; the FDW has to figure out
* which row to delete using data from the planSlot. oldtuple is
@ -1178,15 +1186,17 @@ ldelete:;
* which corrupts your database..
*
* When updating a table, tupleid identifies the tuple to
* update and oldtuple is NULL. When updating a view, oldtuple
* is passed to the INSTEAD OF triggers and identifies what to
* update and oldtuple is NULL. When updating through a view INSTEAD OF
* trigger, oldtuple is passed to the triggers and identifies what to
* update, and tupleid is invalid. When updating a foreign table,
* tupleid is invalid; the FDW has to figure out which row to
* update using data from the planSlot. oldtuple is passed to
* foreign table triggers; it is NULL when the foreign table has
* no relevant triggers.
*
* Returns RETURNING result if any, otherwise NULL.
* Returns RETURNING result if any, otherwise NULL. On exit, if tupleid
* had identified the tuple to update, it will identify the tuple
* actually updated after EvalPlanQual.
* ----------------------------------------------------------------
*/
static TupleTableSlot *
@ -2337,8 +2347,8 @@ ExecModifyTable(PlanState *pstate)
* to set t_tableOid. Quite separately from this, the FDW may
* fetch its own junk attrs to identify the row.
*
* Other relevant relkinds, currently limited to views, always
* have a wholerow attribute.
* Other relevant relkinds, currently limited to views having
* INSTEAD OF triggers, always have a wholerow attribute.
*/
else if (AttributeNumberIsValid(junkfilter->jf_junkAttNo))
{