/*
* Initialize the subplan_map and subpart_map.
*
- * The set of partitions that exist now might not be the same that
- * existed when the plan was made. The normal case is that it is;
- * optimize for that case with a quick comparison, and just copy
- * the subplan_map and make subpart_map point to the one in
- * PruneInfo.
+ * Because we request detached partitions to be included, and
+ * detaching waits for old transactions, it is safe to assume that
+ * no partitions have disappeared since this query was planned.
*
- * For the case where they aren't identical, we could have more
- * partitions on either side; or even exactly the same number of
- * them on both but the set of OIDs doesn't match fully. Handle
- * this by creating new subplan_map and subpart_map arrays that
- * corresponds to the ones in the PruneInfo where the new
- * partition descriptor's OIDs match. Any that don't match can be
- * set to -1, as if they were pruned. Both arrays must be in
- * numerical OID order.
+ * However, new partitions may have been added.
*/
+ Assert(partdesc->nparts >= pinfo->nparts);
pprune->nparts = partdesc->nparts;
pprune->subplan_map = palloc(sizeof(int) * partdesc->nparts);
-
- if (partdesc->nparts == pinfo->nparts &&
- memcmp(partdesc->oids, pinfo->relid_map,
- sizeof(int) * partdesc->nparts) == 0)
+ if (partdesc->nparts == pinfo->nparts)
{
+ /*
+ * There are no new partitions, so this is simple. We can
+ * simply point to the subpart_map from the plan, but we must
+ * copy the subplan_map since we may change it later.
+ */
pprune->subpart_map = pinfo->subpart_map;
memcpy(pprune->subplan_map, pinfo->subplan_map,
sizeof(int) * pinfo->nparts);
+
+ /*
+ * Double-check that the list of unpruned relations has not
+ * changed. (Pruned partitions are not in relid_map[].)
+ */
+#ifdef USE_ASSERT_CHECKING
+ for (int k = 0; k < pinfo->nparts; k++)
+ {
+ Assert(partdesc->oids[k] == pinfo->relid_map[k] ||
+ pinfo->subplan_map[k] == -1);
+ }
+#endif
}
else
{
int pp_idx;
/*
- * When the partition arrays are not identical, there could be
- * some new ones but it's also possible that one was removed;
- * we cope with both situations by walking the arrays and
- * discarding those that don't match.
+ * Some new partitions have appeared since plan time, and
+ * those are reflected in our PartitionDesc but were not
+ * present in the one used to construct subplan_map and
+ * subpart_map. So we must construct new and longer arrays
+ * where the partitions that were originally present map to
+ * the same sub-structures, and any added partitions map to
+ * -1, as if the new partitions had been pruned.
*
- * If the number of partitions on both sides match, it's still
- * possible that one partition has been detached and another
- * attached. Cope with that by creating a map that skips any
- * mismatches.
+ * Note: pinfo->relid_map[] may contain InvalidOid entries for
+ * partitions pruned by the planner. We cannot tell exactly
+ * which of the partdesc entries these correspond to, but we
+ * don't have to; just skip over them. The non-pruned
+ * relid_map entries, however, had better be a subset of the
+ * partdesc entries and in the same order.
*/
pprune->subpart_map = palloc(sizeof(int) * partdesc->nparts);
-
for (pp_idx = 0; pp_idx < partdesc->nparts; pp_idx++)
{
/* Skip any InvalidOid relid_map entries */
!OidIsValid(pinfo->relid_map[pd_idx]))
pd_idx++;
- recheck:
if (pd_idx < pinfo->nparts &&
pinfo->relid_map[pd_idx] == partdesc->oids[pp_idx])
{
pprune->subpart_map[pp_idx] =
pinfo->subpart_map[pd_idx];
pd_idx++;
- continue;
}
-
- /*
- * There isn't an exact match in the corresponding
- * positions of both arrays. Peek ahead in
- * pinfo->relid_map to see if we have a match for the
- * current partition in partdesc. Normally if a match
- * exists it's just one element ahead, and it means the
- * planner saw one extra partition that we no longer see
- * now (its concurrent detach finished just in between);
- * so we skip that one by updating pd_idx to the new
- * location and jumping above. We can then continue to
- * match the rest of the elements after skipping the OID
- * with no match; no future matches are tried for the
- * element that was skipped, because we know the arrays to
- * be in the same order.
- *
- * If we don't see a match anywhere in the rest of the
- * pinfo->relid_map array, that means we see an element
- * now that the planner didn't see, so mark that one as
- * pruned and move on.
- */
- for (int pd_idx2 = pd_idx + 1; pd_idx2 < pinfo->nparts; pd_idx2++)
+ else
{
- if (pd_idx2 >= pinfo->nparts)
- break;
- if (pinfo->relid_map[pd_idx2] == partdesc->oids[pp_idx])
- {
- pd_idx = pd_idx2;
- goto recheck;
- }
+ /* this partdesc entry is not in the plan */
+ pprune->subplan_map[pp_idx] = -1;
+ pprune->subpart_map[pp_idx] = -1;
}
-
- pprune->subpart_map[pp_idx] = -1;
- pprune->subplan_map[pp_idx] = -1;
}
+
+ /*
+ * It might seem that we need to skip any trailing InvalidOid
+ * entries in pinfo->relid_map before checking that we scanned
+ * all of the relid_map. But we will have skipped them above,
+ * because they must correspond to some partdesc->oids
+ * entries; we just couldn't tell which.
+ */
+ if (pd_idx != pinfo->nparts)
+ elog(ERROR, "could not match partition child tables to plan elements");
}
/* present_parts is also subject to later modification */
projects / postgresql.git / commitdiff