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Use TopTransactionContext lifetime for PGSM local data #656

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Use TopTransactionContext lifetime for PGSM local data #656

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53 changes: 46 additions & 7 deletions pg_stat_monitor.c
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Original file line number Diff line number Diff line change
Expand Up @@ -391,13 +391,9 @@ pgsm_post_parse_analyze_internal(ParseState *pstate, Query *query, JumbleState *

if (callback_setup == false)
{
/*
* If MessageContext is valid setup a callback to cleanup our local
* stats list when the MessagContext gets reset
*/
if (MemoryContextIsValid(MessageContext))
if (MemoryContextIsValid(TopTransactionContext))
{
MemoryContextRegisterResetCallback(MessageContext, &mem_cxt_reset_callback);
MemoryContextRegisterResetCallback(TopTransactionContext, &mem_cxt_reset_callback);
Comment on lines +394 to +396
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@artemgavrilov artemgavrilov May 15, 2026

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It seems that TopTransactionContext always exists, no matter how query was executed.

callback_setup = true;
}
}
Expand Down Expand Up @@ -1029,11 +1025,32 @@ pgsm_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
BufferUsage bufusage_start = pgBufferUsage;
WalUsage walusage;
WalUsage walusage_start = pgWalUsage;
pgsmEntry *entry = pgsm_create_hash_entry(0, queryId, NULL);
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@artemgavrilov artemgavrilov May 15, 2026

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We cannot invoke this function here anymore, as some utility queries create and finish multiple transactions during its processing. Vacuum for example. But we still need username and application name that triggered the query. Without this SET application_name = new app will log new app as query tirgger.

int64 appid;
char *datname = NULL;
char *username = NULL;
pgsmEntry *entry = NULL;

if (getrusage(RUSAGE_SELF, &rusage_start) != 0)
elog(DEBUG1, "[pg_stat_monitor] pgsm_ProcessUtility: Failed to execute getrusage.");

/* Prefetch application name before executing the utility process as it may change value */
if (pgsm_track_application_names)
{
/* Get the application name and set appid */
int app_name_len = pg_get_application_name(app_name, APPLICATIONNAME_LEN);
appid = pgsm_hash_string((const char *) app_name, app_name_len);
}

/* Prefetch database name and username before executing the utility as they may change value */
if (IsTransactionState())
{
int userid;
int sec_ctx;
datname = get_database_name(MyDatabaseId);
GetUserIdAndSecContext((Oid *) &userid, &sec_ctx);
username = GetUserNameFromId(userid, true);
}

INSTR_TIME_SET_CURRENT(start);
nesting_level++;

Expand Down Expand Up @@ -1094,6 +1111,24 @@ pgsm_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
query_len = pstmt->stmt_len;
query_text = (char *) CleanQuerytext(queryString, &location, &query_len);

/* Create entry after utility process because we need allocations and some utilities
* may create multiple transactions that will cause memory cleanup
*/
entry = pgsm_create_hash_entry(0, queryId, NULL);

/* Update the entry with the prefetched data */
entry->key.appid = appid;

if (datname){
snprintf(entry->datname, sizeof(entry->datname), "%s", datname);
pfree(datname);
}

if (username){
snprintf(entry->username, sizeof(entry->username), "%s", username);
pfree(username);
}

entry->pgsm_query_id = get_pgsm_query_id_hash(query_text, query_len);
entry->counters.info.cmd_type = pstmt->commandType;

Expand Down Expand Up @@ -1122,6 +1157,7 @@ pgsm_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
PGSM_EXEC); /* kind */

pgsm_store(entry);
pgsm_delete_entry(queryId);
}
else
{
Expand Down Expand Up @@ -1710,6 +1746,9 @@ pgsm_create_hash_entry(uint64 bucket_id, int64 queryid, PlanInfo *plan_info)

if (pgsm_track_application_names)
{
/* TODO: Move app name fetching out of this function
* because at this point app name may be changed by the query itself

/* Get the application name and set appid */
app_name_len = pg_get_application_name(app_name, APPLICATIONNAME_LEN);
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@artemgavrilov artemgavrilov May 15, 2026

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This line updates global variable app_name, we shouldn't do it here as it affects what app name will be logged for SET application_name = new app query.

entry->key.appid = pgsm_hash_string((const char *) app_name, app_name_len);
Expand Down
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