pgstat: Prepare to use mechanism for truncated rels also for droppped rels.

The upcoming shared memory stats patch drops stats for dropped objects in a
transactional manner, rather than removing them later as part of vacuum. This
means that stats for DROP inside a transaction needs to handle aborted
(sub-)transactions similar to TRUNCATE: The stats up to the DROP should be
restored.

Rename the existing infrastructure in preparation.

Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20210405092914.mmxqe7j56lsjfsej@alap3.anarazel.de

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index 69e89e4dec58633a53363b05accf4da4bb9c6434..b7d0fbaefddb005cf756b9675dfbdf4bbe1c151a 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -257,12 +257,13 @@ typedef struct TwoPhasePgStatRecord
        PgStat_Counter tuples_inserted; /* tuples inserted in xact */
        PgStat_Counter tuples_updated;  /* tuples updated in xact */
        PgStat_Counter tuples_deleted;  /* tuples deleted in xact */
-       PgStat_Counter inserted_pre_trunc;      /* tuples inserted prior to truncate */
-       PgStat_Counter updated_pre_trunc;       /* tuples updated prior to truncate */
-       PgStat_Counter deleted_pre_trunc;       /* tuples deleted prior to truncate */
+       /* tuples i/u/d prior to truncate/drop */
+       PgStat_Counter inserted_pre_truncdrop;
+       PgStat_Counter updated_pre_truncdrop;
+       PgStat_Counter deleted_pre_truncdrop;
        Oid                     t_id;                   /* table's OID */
        bool            t_shared;               /* is it a shared catalog? */
-       bool            t_truncated;    /* was the relation truncated? */
+       bool            t_truncdropped; /* was the relation truncated/dropped? */
 } TwoPhasePgStatRecord;
 
 /*
@@ -2300,36 +2301,39 @@ pgstat_count_heap_delete(Relation rel)
 }
 
 /*
- * pgstat_truncate_save_counters
+ * pgstat_truncdrop_save_counters
  *
- * Whenever a table is truncated, we save its i/u/d counters so that they can
- * be cleared, and if the (sub)xact that executed the truncate later aborts,
- * the counters can be restored to the saved (pre-truncate) values.  Note we do
- * this on the first truncate in any particular subxact level only.
+ * Whenever a table is truncated/dropped, we save its i/u/d counters so that
+ * they can be cleared, and if the (sub)xact that executed the truncate/drop
+ * later aborts, the counters can be restored to the saved (pre-truncate/drop)
+ * values.
+ *
+ * Note that for truncate we do this on the first truncate in any particular
+ * subxact level only.
  */
 static void
-pgstat_truncate_save_counters(PgStat_TableXactStatus *trans)
+pgstat_truncdrop_save_counters(PgStat_TableXactStatus *trans, bool is_drop)
 {
-       if (!trans->truncated)
+       if (!trans->truncdropped || is_drop)
        {
-               trans->inserted_pre_trunc = trans->tuples_inserted;
-               trans->updated_pre_trunc = trans->tuples_updated;
-               trans->deleted_pre_trunc = trans->tuples_deleted;
-               trans->truncated = true;
+               trans->inserted_pre_truncdrop = trans->tuples_inserted;
+               trans->updated_pre_truncdrop = trans->tuples_updated;
+               trans->deleted_pre_truncdrop = trans->tuples_deleted;
+               trans->truncdropped = true;
        }
 }
 
 /*
- * pgstat_truncate_restore_counters - restore counters when a truncate aborts
+ * pgstat_truncdrop_restore_counters - restore counters when a truncate aborts
  */
 static void
-pgstat_truncate_restore_counters(PgStat_TableXactStatus *trans)
+pgstat_truncdrop_restore_counters(PgStat_TableXactStatus *trans)
 {
-       if (trans->truncated)
+       if (trans->truncdropped)
        {
-               trans->tuples_inserted = trans->inserted_pre_trunc;
-               trans->tuples_updated = trans->updated_pre_trunc;
-               trans->tuples_deleted = trans->deleted_pre_trunc;
+               trans->tuples_inserted = trans->inserted_pre_truncdrop;
+               trans->tuples_updated = trans->updated_pre_truncdrop;
+               trans->tuples_deleted = trans->deleted_pre_truncdrop;
        }
 }
 
@@ -2350,7 +2354,7 @@ pgstat_count_truncate(Relation rel)
                        pgstat_info->trans->nest_level != nest_level)
                        add_tabstat_xact_level(pgstat_info, nest_level);
 
-               pgstat_truncate_save_counters(pgstat_info->trans);
+               pgstat_truncdrop_save_counters(pgstat_info->trans, false);
                pgstat_info->trans->tuples_inserted = 0;
                pgstat_info->trans->tuples_updated = 0;
                pgstat_info->trans->tuples_deleted = 0;
@@ -2395,17 +2399,17 @@ AtEOXact_PgStat_Relations(PgStat_SubXactStatus *xact_state, bool isCommit)
                Assert(trans->upper == NULL);
                tabstat = trans->parent;
                Assert(tabstat->trans == trans);
-               /* restore pre-truncate stats (if any) in case of aborted xact */
+               /* restore pre-truncate/drop stats (if any) in case of aborted xact */
                if (!isCommit)
-                       pgstat_truncate_restore_counters(trans);
+                       pgstat_truncdrop_restore_counters(trans);
                /* count attempted actions regardless of commit/abort */
                tabstat->t_counts.t_tuples_inserted += trans->tuples_inserted;
                tabstat->t_counts.t_tuples_updated += trans->tuples_updated;
                tabstat->t_counts.t_tuples_deleted += trans->tuples_deleted;
                if (isCommit)
                {
-                       tabstat->t_counts.t_truncated = trans->truncated;
-                       if (trans->truncated)
+                       tabstat->t_counts.t_truncdropped = trans->truncdropped;
+                       if (trans->truncdropped)
                        {
                                /* forget live/dead stats seen by backend thus far */
                                tabstat->t_counts.t_delta_live_tuples = 0;
@@ -2504,10 +2508,10 @@ AtEOSubXact_PgStat_Relations(PgStat_SubXactStatus *xact_state, bool isCommit, in
                {
                        if (trans->upper && trans->upper->nest_level == nestDepth - 1)
                        {
-                               if (trans->truncated)
+                               if (trans->truncdropped)
                                {
-                                       /* propagate the truncate status one level up */
-                                       pgstat_truncate_save_counters(trans->upper);
+                                       /* propagate the truncate/drop status one level up */
+                                       pgstat_truncdrop_save_counters(trans->upper, false);
                                        /* replace upper xact stats with ours */
                                        trans->upper->tuples_inserted = trans->tuples_inserted;
                                        trans->upper->tuples_updated = trans->tuples_updated;
@@ -2547,8 +2551,8 @@ AtEOSubXact_PgStat_Relations(PgStat_SubXactStatus *xact_state, bool isCommit, in
                         * subtransaction
                         */
 
-                       /* first restore values obliterated by truncate */
-                       pgstat_truncate_restore_counters(trans);
+                       /* first restore values obliterated by truncate/drop */
+                       pgstat_truncdrop_restore_counters(trans);
                        /* count attempted actions regardless of commit/abort */
                        tabstat->t_counts.t_tuples_inserted += trans->tuples_inserted;
                        tabstat->t_counts.t_tuples_updated += trans->tuples_updated;
@@ -2609,12 +2613,12 @@ AtPrepare_PgStat_Relations(PgStat_SubXactStatus *xact_state)
                record.tuples_inserted = trans->tuples_inserted;
                record.tuples_updated = trans->tuples_updated;
                record.tuples_deleted = trans->tuples_deleted;
-               record.inserted_pre_trunc = trans->inserted_pre_trunc;
-               record.updated_pre_trunc = trans->updated_pre_trunc;
-               record.deleted_pre_trunc = trans->deleted_pre_trunc;
+               record.inserted_pre_truncdrop = trans->inserted_pre_truncdrop;
+               record.updated_pre_truncdrop = trans->updated_pre_truncdrop;
+               record.deleted_pre_truncdrop = trans->deleted_pre_truncdrop;
                record.t_id = tabstat->t_id;
                record.t_shared = tabstat->t_shared;
-               record.t_truncated = trans->truncated;
+               record.t_truncdropped = trans->truncdropped;
 
                RegisterTwoPhaseRecord(TWOPHASE_RM_PGSTAT_ID, 0,
                                                           &record, sizeof(TwoPhasePgStatRecord));
@@ -2710,8 +2714,8 @@ pgstat_twophase_postcommit(TransactionId xid, uint16 info,
        pgstat_info->t_counts.t_tuples_inserted += rec->tuples_inserted;
        pgstat_info->t_counts.t_tuples_updated += rec->tuples_updated;
        pgstat_info->t_counts.t_tuples_deleted += rec->tuples_deleted;
-       pgstat_info->t_counts.t_truncated = rec->t_truncated;
-       if (rec->t_truncated)
+       pgstat_info->t_counts.t_truncdropped = rec->t_truncdropped;
+       if (rec->t_truncdropped)
        {
                /* forget live/dead stats seen by backend thus far */
                pgstat_info->t_counts.t_delta_live_tuples = 0;
@@ -2743,11 +2747,11 @@ pgstat_twophase_postabort(TransactionId xid, uint16 info,
        pgstat_info = get_tabstat_entry(rec->t_id, rec->t_shared);
 
        /* Same math as in AtEOXact_PgStat, abort case */
-       if (rec->t_truncated)
+       if (rec->t_truncdropped)
        {
-               rec->tuples_inserted = rec->inserted_pre_trunc;
-               rec->tuples_updated = rec->updated_pre_trunc;
-               rec->tuples_deleted = rec->deleted_pre_trunc;
+               rec->tuples_inserted = rec->inserted_pre_truncdrop;
+               rec->tuples_updated = rec->updated_pre_truncdrop;
+               rec->tuples_deleted = rec->deleted_pre_truncdrop;
        }
        pgstat_info->t_counts.t_tuples_inserted += rec->tuples_inserted;
        pgstat_info->t_counts.t_tuples_updated += rec->tuples_updated;
@@ -5055,8 +5059,11 @@ pgstat_recv_tabstat(PgStat_MsgTabstat *msg, int len)
                        tabentry->tuples_updated += tabmsg->t_counts.t_tuples_updated;
                        tabentry->tuples_deleted += tabmsg->t_counts.t_tuples_deleted;
                        tabentry->tuples_hot_updated += tabmsg->t_counts.t_tuples_hot_updated;
-                       /* If table was truncated, first reset the live/dead counters */
-                       if (tabmsg->t_counts.t_truncated)
+                       /*
+                        * If table was truncated/dropped, first reset the live/dead
+                        * counters.
+                        */
+                       if (tabmsg->t_counts.t_truncdropped)
                        {
                                tabentry->n_live_tuples = 0;
                                tabentry->n_dead_tuples = 0;

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index a7b386821f6d603038383354ac715032bf9147e6..bcd3588ea2989077fda5aa6c8e3c3073f57ed39e 100644 (file)
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -123,7 +123,7 @@ typedef struct PgStat_TableCounts
        PgStat_Counter t_tuples_updated;
        PgStat_Counter t_tuples_deleted;
        PgStat_Counter t_tuples_hot_updated;
-       bool            t_truncated;
+       bool            t_truncdropped;
 
        PgStat_Counter t_delta_live_tuples;
        PgStat_Counter t_delta_dead_tuples;
@@ -186,10 +186,12 @@ typedef struct PgStat_TableXactStatus
        PgStat_Counter tuples_inserted; /* tuples inserted in (sub)xact */
        PgStat_Counter tuples_updated;  /* tuples updated in (sub)xact */
        PgStat_Counter tuples_deleted;  /* tuples deleted in (sub)xact */
-       bool            truncated;              /* relation truncated in this (sub)xact */
-       PgStat_Counter inserted_pre_trunc;      /* tuples inserted prior to truncate */
-       PgStat_Counter updated_pre_trunc;       /* tuples updated prior to truncate */
-       PgStat_Counter deleted_pre_trunc;       /* tuples deleted prior to truncate */
+       bool            truncdropped;           /* relation truncated/dropped in this
+                                                                        * (sub)xact */
+       /* tuples i/u/d prior to truncate/drop */
+       PgStat_Counter inserted_pre_truncdrop;
+       PgStat_Counter updated_pre_truncdrop;
+       PgStat_Counter deleted_pre_truncdrop;
        int                     nest_level;             /* subtransaction nest level */
        /* links to other structs for same relation: */
        struct PgStat_TableXactStatus *upper;   /* next higher subxact if any */