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 */