Don't fetch partition check expression during InitResultRelInfo.

Since there is only one place that actually needs the partition check
expression, namely ExecPartitionCheck, it's better to fetch it from
the relcache there.  In this way we will never fetch it at all if
the query never has use for it, and we still fetch it just once when
we do need it.

The reason for taking an interest in this is that if the relcache
doesn't already have the check expression cached, fetching it
requires obtaining AccessShareLock on the partition root.  That
means that operations that look like they should only touch the
partition itself will also take a lock on the root.  In particular
we observed that TRUNCATE on a partition may take a lock on the
partition's root, contributing to a deadlock situation in parallel
pg_restore.

As written, this patch does have a small cost, which is that we
are microscopically reducing efficiency for the case where a partition
has an empty check expression.  ExecPartitionCheck will be called,
and will go through the motions of setting up and checking an empty
qual, where before it would not have been called at all.  We could
avoid that by adding a separate boolean flag to track whether there
is a partition expression to test.  However, this case only arises
for a default partition with no siblings, which surely is not an
interesting case in practice.  Hence adding complexity for it
does not seem like a good trade-off.

Amit Langote, per a suggestion by me

Discussion: https://postgr.es/m/VI1PR03MB31670CA1BD9625C3A8C5DD05EB230@VI1PR03MB3167.eurprd03.prod.outlook.com

diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index db7d24a511e3b468d514b7a5bcc9ec21d13596a5..2047557e52005ee2cef590e4847f87d446b3ea55 100644 (file)
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -3236,7 +3236,7 @@ CopyFrom(CopyState cstate)
                 * we don't need to if there's no BR trigger defined on the
                 * partition.
                 */
-               if (resultRelInfo->ri_PartitionCheck &&
+               if (resultRelInfo->ri_RelationDesc->rd_rel->relispartition &&
                    (proute == NULL || has_before_insert_row_trig))
                    ExecPartitionCheck(resultRelInfo, myslot, estate, true);
 

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 4fdffad6f35dfaefe1eb503b244f73ee5cc1a570..2e27e26ba44652b51fc2c9603f93730e945744ad 100644 (file)
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -1280,8 +1280,6 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
                  Relation partition_root,
                  int instrument_options)
 {
-   List       *partition_check = NIL;
-
    MemSet(resultRelInfo, 0, sizeof(ResultRelInfo));
    resultRelInfo->type = T_ResultRelInfo;
    resultRelInfo->ri_RangeTableIndex = resultRelationIndex;
@@ -1325,23 +1323,6 @@ InitResultRelInfo(ResultRelInfo *resultRelInfo,
    resultRelInfo->ri_ReturningSlot = NULL;
    resultRelInfo->ri_TrigOldSlot = NULL;
    resultRelInfo->ri_TrigNewSlot = NULL;
-
-   /*
-    * Partition constraint, which also includes the partition constraint of
-    * all the ancestors that are partitions.  Note that it will be checked
-    * even in the case of tuple-routing where this table is the target leaf
-    * partition, if there any BR triggers defined on the table.  Although
-    * tuple-routing implicitly preserves the partition constraint of the
-    * target partition for a given row, the BR triggers may change the row
-    * such that the constraint is no longer satisfied, which we must fail for
-    * by checking it explicitly.
-    *
-    * If this is a partitioned table, the partition constraint (if any) of a
-    * given row will be checked just before performing tuple-routing.
-    */
-   partition_check = RelationGetPartitionQual(resultRelationDesc);
-
-   resultRelInfo->ri_PartitionCheck = partition_check;
    resultRelInfo->ri_PartitionRoot = partition_root;
    resultRelInfo->ri_PartitionInfo = NULL; /* may be set later */
    resultRelInfo->ri_CopyMultiInsertBuffer = NULL;
@@ -1776,7 +1757,7 @@ ExecRelCheck(ResultRelInfo *resultRelInfo,
  * ExecPartitionCheck --- check that tuple meets the partition constraint.
  *
  * Returns true if it meets the partition constraint.  If the constraint
- * fails and we're asked to emit to error, do so and don't return; otherwise
+ * fails and we're asked to emit an error, do so and don't return; otherwise
  * return false.
  */
 bool
@@ -1788,14 +1769,22 @@ ExecPartitionCheck(ResultRelInfo *resultRelInfo, TupleTableSlot *slot,
 
    /*
     * If first time through, build expression state tree for the partition
-    * check expression.  Keep it in the per-query memory context so they'll
-    * survive throughout the query.
+    * check expression.  (In the corner case where the partition check
+    * expression is empty, ie there's a default partition and nothing else,
+    * we'll be fooled into executing this code each time through.  But it's
+    * pretty darn cheap in that case, so we don't worry about it.)
     */
    if (resultRelInfo->ri_PartitionCheckExpr == NULL)
    {
-       List       *qual = resultRelInfo->ri_PartitionCheck;
+       /*
+        * Ensure that the qual tree and prepared expression are in the
+        * query-lifespan context.
+        */
+       MemoryContext oldcxt = MemoryContextSwitchTo(estate->es_query_cxt);
+       List       *qual = RelationGetPartitionQual(resultRelInfo->ri_RelationDesc);
 
        resultRelInfo->ri_PartitionCheckExpr = ExecPrepareCheck(qual, estate);
+       MemoryContextSwitchTo(oldcxt);
    }
 
    /*
@@ -1904,9 +1893,9 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
    Bitmapset  *insertedCols;
    Bitmapset  *updatedCols;
 
-   Assert(constr || resultRelInfo->ri_PartitionCheck);
+   Assert(constr);             /* we should not be called otherwise */
 
-   if (constr && constr->has_not_null)
+   if (constr->has_not_null)
    {
        int         natts = tupdesc->natts;
        int         attrChk;
@@ -1967,7 +1956,7 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
        }
    }
 
-   if (constr && constr->num_check > 0)
+   if (constr->num_check > 0)
    {
        const char *failed;
 

diff --git a/src/backend/executor/execPartition.c b/src/backend/executor/execPartition.c
index bd2ea2580475f7c9d6b126ec7c898b2c2eef38e5..33d2c6f63de4a15b9d1d60f7f49c914e58d155fe 100644 (file)
--- a/src/backend/executor/execPartition.c
+++ b/src/backend/executor/execPartition.c
@@ -299,7 +299,7 @@ ExecFindPartition(ModifyTableState *mtstate,
     * First check the root table's partition constraint, if any.  No point in
     * routing the tuple if it doesn't belong in the root table itself.
     */
-   if (rootResultRelInfo->ri_PartitionCheck)
+   if (rootResultRelInfo->ri_RelationDesc->rd_rel->relispartition)
        ExecPartitionCheck(rootResultRelInfo, slot, estate, true);
 
    /* start with the root partitioned table */

diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index 8f474faed066a46b88c1275a4a07db34327c9712..b29db7bf4f9566f7e8f563ca3f9bcb43bc25359b 100644 (file)
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -435,7 +435,7 @@ ExecSimpleRelationInsert(EState *estate, TupleTableSlot *slot)
        /* Check the constraints of the tuple */
        if (rel->rd_att->constr)
            ExecConstraints(resultRelInfo, slot, estate);
-       if (resultRelInfo->ri_PartitionCheck)
+       if (rel->rd_rel->relispartition)
            ExecPartitionCheck(resultRelInfo, slot, estate, true);
 
        /* OK, store the tuple and create index entries for it */
@@ -501,7 +501,7 @@ ExecSimpleRelationUpdate(EState *estate, EPQState *epqstate,
        /* Check the constraints of the tuple */
        if (rel->rd_att->constr)
            ExecConstraints(resultRelInfo, slot, estate);
-       if (resultRelInfo->ri_PartitionCheck)
+       if (rel->rd_rel->relispartition)
            ExecPartitionCheck(resultRelInfo, slot, estate, true);
 
        simple_table_tuple_update(rel, tid, slot, estate->es_snapshot,

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 20a4c474cc47f5e1ee8ffba4444d2e19f1e255e0..98120891619b0ecb0f24d4f93af11bdc6347d368 100644 (file)
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -491,7 +491,7 @@ ExecInsert(ModifyTableState *mtstate,
         * one; except that if we got here via tuple-routing, we don't need to
         * if there's no BR trigger defined on the partition.
         */
-       if (resultRelInfo->ri_PartitionCheck &&
+       if (resultRelationDesc->rd_rel->relispartition &&
            (resultRelInfo->ri_PartitionRoot == NULL ||
             (resultRelInfo->ri_TrigDesc &&
              resultRelInfo->ri_TrigDesc->trig_insert_before_row)))
@@ -1181,7 +1181,7 @@ lreplace:;
         * row.  So skip the WCO checks if the partition constraint fails.
         */
        partition_constraint_failed =
-           resultRelInfo->ri_PartitionCheck &&
+           resultRelationDesc->rd_rel->relispartition &&
            !ExecPartitionCheck(resultRelInfo, slot, estate, false);
 
        if (!partition_constraint_failed &&

diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index c37aafed0d29eb5a97d07afa5b131fd411e2181b..d239d28c094b90249006b52eb0393ac94319d212 100644 (file)
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -1676,7 +1676,7 @@ apply_handle_tuple_routing(ResultRelInfo *relinfo,
                 * Does the updated tuple still satisfy the current
                 * partition's constraint?
                 */
-               if (partrelinfo->ri_PartitionCheck == NULL ||
+               if (!partrel->rd_rel->relispartition ||
                    ExecPartitionCheck(partrelinfo, remoteslot_part, estate,
                                       false))
                {

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 0b42dd6f9441090484eb5fd451317b1325ff1290..a5ab1aed14d5af6b475f75b7256f24e92e345014 100644 (file)
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -477,19 +477,16 @@ typedef struct ResultRelInfo
    /* ON CONFLICT evaluation state */
    OnConflictSetState *ri_onConflict;
 
-   /* partition check expression */
-   List       *ri_PartitionCheck;
-
-   /* partition check expression state */
+   /* partition check expression state (NULL if not set up yet) */
    ExprState  *ri_PartitionCheckExpr;
 
-   /* relation descriptor for root partitioned table */
+   /* relation descriptor for partitioned table's root, if any */
    Relation    ri_PartitionRoot;
 
-   /* Additional information specific to partition tuple routing */
+   /* info for partition tuple routing (NULL if not set up yet) */
    struct PartitionRoutingInfo *ri_PartitionInfo;
 
-   /* For use by copy.c when performing multi-inserts */
+   /* for use by copy.c when performing multi-inserts */
    struct CopyMultiInsertBuffer *ri_CopyMultiInsertBuffer;
 } ResultRelInfo;