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pgstat: separate "xact level" handling out of relation specific functions.
This is in preparation of a later commit moving relation stats handling into its own file. Author: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de
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‎src/backend/postmaster/pgstat.c

+35-33
Original file line numberDiff line numberDiff line change
@@ -235,16 +235,24 @@ static bool have_relation_stats = false;
235235
static bool have_function_stats = false;
236236

237237
/*
238-
* Tuple insertion/deletion counts for an open transaction can't be propagated
239-
* into PgStat_TableStatus counters until we know if it is going to commit
240-
* or abort. Hence, we keep these counts in per-subxact structs that live
241-
* in TopTransactionContext. This data structure is designed on the assumption
242-
* that subxacts won't usually modify very many tables.
238+
* Some stats changes are transactional. To maintain those, a stack of
239+
* PgStat_SubXactStatus entries is maintained, which contain data pertaining
240+
* to the current transaction and its active subtransactions.
243241
*/
244242
typedef struct PgStat_SubXactStatus
245243
{
246244
int nest_level; /* subtransaction nest level */
245+
247246
struct PgStat_SubXactStatus *prev; /* higher-level subxact if any */
247+
248+
/*
249+
* Tuple insertion/deletion counts for an open transaction can't be
250+
* propagated into PgStat_TableStatus counters until we know if it is
251+
* going to commit or abort. Hence, we keep these counts in per-subxact
252+
* structs that live in TopTransactionContext. This data structure is
253+
* designed on the assumption that subxacts won't usually modify very many
254+
* tables.
255+
*/
248256
PgStat_TableXactStatus *first; /* head of list for this subxact */
249257
} PgStat_SubXactStatus;
250258

@@ -2305,10 +2313,11 @@ find_tabstat_entry(Oid rel_id)
23052313
}
23062314

23072315
/*
2308-
* get_tabstat_stack_level - add a new (sub)transaction stack entry if needed
2316+
* Ensure (sub)transaction stack entry for the given nest_level exists, adding
2317+
* it if needed.
23092318
*/
23102319
static PgStat_SubXactStatus *
2311-
get_tabstat_stack_level(int nest_level)
2320+
pgstat_xact_stack_level_get(int nest_level)
23122321
{
23132322
PgStat_SubXactStatus *xact_state;
23142323

@@ -2339,7 +2348,7 @@ add_tabstat_xact_level(PgStat_TableStatus *pgstat_info, int nest_level)
23392348
* If this is the first rel to be modified at the current nest level, we
23402349
* first have to push a transaction stack entry.
23412350
*/
2342-
xact_state = get_tabstat_stack_level(nest_level);
2351+
xact_state = pgstat_xact_stack_level_get(nest_level);
23432352

23442353
/* Now make a per-table stack entry */
23452354
trans = (PgStat_TableXactStatus *)
@@ -2353,6 +2362,19 @@ add_tabstat_xact_level(PgStat_TableStatus *pgstat_info, int nest_level)
23532362
pgstat_info->trans = trans;
23542363
}
23552364

2365+
/*
2366+
* Add a new (sub)transaction record if needed.
2367+
*/
2368+
static void
2369+
ensure_tabstat_xact_level(PgStat_TableStatus *pgstat_info)
2370+
{
2371+
int nest_level = GetCurrentTransactionNestLevel();
2372+
2373+
if (pgstat_info->trans == NULL ||
2374+
pgstat_info->trans->nest_level != nest_level)
2375+
add_tabstat_xact_level(pgstat_info, nest_level);
2376+
}
2377+
23562378
/*
23572379
* pgstat_count_heap_insert - count a tuple insertion of n tuples
23582380
*/
@@ -2362,13 +2384,8 @@ pgstat_count_heap_insert(Relation rel, PgStat_Counter n)
23622384
if (pgstat_relation_should_count(rel))
23632385
{
23642386
PgStat_TableStatus *pgstat_info = rel->pgstat_info;
2365-
int nest_level = GetCurrentTransactionNestLevel();
2366-
2367-
/* We have to log the effect at the proper transactional level */
2368-
if (pgstat_info->trans == NULL ||
2369-
pgstat_info->trans->nest_level != nest_level)
2370-
add_tabstat_xact_level(pgstat_info, nest_level);
23712387

2388+
ensure_tabstat_xact_level(pgstat_info);
23722389
pgstat_info->trans->tuples_inserted += n;
23732390
}
23742391
}
@@ -2382,13 +2399,8 @@ pgstat_count_heap_update(Relation rel, bool hot)
23822399
if (pgstat_relation_should_count(rel))
23832400
{
23842401
PgStat_TableStatus *pgstat_info = rel->pgstat_info;
2385-
int nest_level = GetCurrentTransactionNestLevel();
2386-
2387-
/* We have to log the effect at the proper transactional level */
2388-
if (pgstat_info->trans == NULL ||
2389-
pgstat_info->trans->nest_level != nest_level)
2390-
add_tabstat_xact_level(pgstat_info, nest_level);
23912402

2403+
ensure_tabstat_xact_level(pgstat_info);
23922404
pgstat_info->trans->tuples_updated++;
23932405

23942406
/* t_tuples_hot_updated is nontransactional, so just advance it */
@@ -2406,13 +2418,8 @@ pgstat_count_heap_delete(Relation rel)
24062418
if (pgstat_relation_should_count(rel))
24072419
{
24082420
PgStat_TableStatus *pgstat_info = rel->pgstat_info;
2409-
int nest_level = GetCurrentTransactionNestLevel();
2410-
2411-
/* We have to log the effect at the proper transactional level */
2412-
if (pgstat_info->trans == NULL ||
2413-
pgstat_info->trans->nest_level != nest_level)
2414-
add_tabstat_xact_level(pgstat_info, nest_level);
24152421

2422+
ensure_tabstat_xact_level(pgstat_info);
24162423
pgstat_info->trans->tuples_deleted++;
24172424
}
24182425
}
@@ -2463,13 +2470,8 @@ pgstat_count_truncate(Relation rel)
24632470
if (pgstat_relation_should_count(rel))
24642471
{
24652472
PgStat_TableStatus *pgstat_info = rel->pgstat_info;
2466-
int nest_level = GetCurrentTransactionNestLevel();
2467-
2468-
/* We have to log the effect at the proper transactional level */
2469-
if (pgstat_info->trans == NULL ||
2470-
pgstat_info->trans->nest_level != nest_level)
2471-
add_tabstat_xact_level(pgstat_info, nest_level);
24722473

2474+
ensure_tabstat_xact_level(pgstat_info);
24732475
pgstat_truncdrop_save_counters(pgstat_info->trans, false);
24742476
pgstat_info->trans->tuples_inserted = 0;
24752477
pgstat_info->trans->tuples_updated = 0;
@@ -2656,7 +2658,7 @@ AtEOSubXact_PgStat_Relations(PgStat_SubXactStatus *xact_state, bool isCommit, in
26562658
*/
26572659
PgStat_SubXactStatus *upper_xact_state;
26582660

2659-
upper_xact_state = get_tabstat_stack_level(nestDepth - 1);
2661+
upper_xact_state = pgstat_xact_stack_level_get(nestDepth - 1);
26602662
trans->next = upper_xact_state->first;
26612663
upper_xact_state->first = trans;
26622664
trans->nest_level = nestDepth - 1;

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