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Calculate extraUpdatedCols in query rewriter, not parser.

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It's unsafe to do this at parse time because addition of generated
columns to a table would not invalidate stored rules containing
UPDATEs on the table ... but there might now be dependent generated
columns that were not there when the rule was made.  This also fixes
an oversight that rewriteTargetView failed to update extraUpdatedCols
when transforming an UPDATE on an updatable view.  (Since the new
calculation is downstream of that, rewriteTargetView doesn't actually
need to do anything; but before, there was a demonstrable bug there.)

In v13 and HEAD, this leads to easily-visible bugs because (since
commit c6679e4fc) we won't recalculate generated columns that aren't
listed in extraUpdatedCols.  In v12 this bitmap is mostly just used
for trigger-firing decisions, so you'd only notice a problem if a
trigger cared whether a generated column had been updated.

I'd complained about this back in May, but then forgot about it
until bug #16671 from Michael Paul Killian revived the issue.

Back-patch to v12 where this field was introduced.  If existing
stored rules contain any extraUpdatedCols values, they'll be
ignored because the rewriter will overwrite them, so the bug will
be fixed even for existing rules.  (But note that if someone were
to update to 13.1 or 12.5, store some rules with UPDATEs on tables
having generated columns, and then downgrade to a prior minor version,
they might observe issues similar to what this patch fixes.  That
seems unlikely enough to not be worth going to a lot of effort to fix.)

Discussion: https://postgr.es/m/10206.1588964727@sss.pgh.pa.us
Discussion: https://postgr.es/m/16671-2fa55851859fb166@postgresql.org
This commit is contained in:
Tom Lane
2020-10-28 13:47:02 -04:00
parent 36b9312143
commit ad77039fad
9 changed files with 115 additions and 47 deletions
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6
src/backend/optimizer/plan/setrefs.c
View File

@ -438,9 +438,9 @@ flatten_rtes_walker(Node *node, PlannerGlobal *glob)
* In the flat rangetable, we zero out substructure pointers that are not
* needed by the executor; this reduces the storage space and copying cost
* for cached plans. We keep only the ctename, alias and eref Alias fields,
* which are needed by EXPLAIN, and the selectedCols, insertedCols and
* updatedCols bitmaps, which are needed for executor-startup permissions
* checking and for trigger event checking.
* which are needed by EXPLAIN, and the selectedCols, insertedCols,
* updatedCols, and extraUpdatedCols bitmaps, which are needed for
* executor-startup permissions checking and for trigger event checking.
*/
static void
add_rte_to_flat_rtable(PlannerGlobal *glob, RangeTblEntry *rte)