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Jul 2, 2024
Merged

Add option for tracking subqueries' wait events #80

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7 changes: 4 additions & 3 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -139,15 +139,16 @@ GUCs.
| pg_wait_sampling.history_period | int4 | Period for history sampling in milliseconds | 10 |
| pg_wait_sampling.profile_period | int4 | Period for profile sampling in milliseconds | 10 |
| pg_wait_sampling.profile_pid | bool | Whether profile should be per pid | true |
| pg_wait_sampling.profile_queries | bool | Whether profile should be per query | true |
| pg_wait_sampling.profile_queries | enum | Whether profile should be per query | top |
| pg_wait_sampling.sample_cpu | bool | Whether on CPU backends should be sampled | true |

If `pg_wait_sampling.profile_pid` is set to false, sampling profile wouldn't be
collected in per-process manner. In this case the value of pid could would
be always zero and corresponding row contain samples among all the processes.

While `pg_wait_sampling.profile_queries` is set to false `queryid` field in
views will be zero.
If `pg_wait_sampling.profile_queries` is set to `none`, `queryid` field in
views will be zero. If it is set to `top`, queryIds only of top level statements
are recorded. If it is set to `all`, queryIds of nested statements are recorded.

If `pg_wait_sampling.sample_cpu` is set to true then processes that are not
waiting on anything are also sampled. The wait event columns for such processes
Expand Down
98 changes: 86 additions & 12 deletions pg_wait_sampling.c
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,35 @@ static void pgws_ProcessUtility(PlannedStmt *pstmt,
#endif
);

/*---- GUC variables ----*/

typedef enum
{
PGWS_PROFILE_QUERIES_NONE, /* profile no statements */
PGWS_PROFILE_QUERIES_TOP, /* only top level statements */
PGWS_PROFILE_QUERIES_ALL /* all statements, including nested ones */
} PGWSTrackLevel;

static const struct config_enum_entry pgws_profile_queries_options[] =
{
{"none", PGWS_PROFILE_QUERIES_NONE, false},
{"off", PGWS_PROFILE_QUERIES_NONE, false},
{"no", PGWS_PROFILE_QUERIES_NONE, false},
{"false", PGWS_PROFILE_QUERIES_NONE, false},
{"0", PGWS_PROFILE_QUERIES_NONE, false},
{"top", PGWS_PROFILE_QUERIES_TOP, false},
{"on", PGWS_PROFILE_QUERIES_TOP, false},
{"yes", PGWS_PROFILE_QUERIES_TOP, false},
{"true", PGWS_PROFILE_QUERIES_TOP, false},
{"1", PGWS_PROFILE_QUERIES_TOP, false},
{"all", PGWS_PROFILE_QUERIES_ALL, false},
{NULL, 0, false}
};

#define pgws_enabled(level) \
((pgws_collector_hdr->profileQueries == PGWS_PROFILE_QUERIES_ALL) || \
(pgws_collector_hdr->profileQueries == PGWS_PROFILE_QUERIES_TOP && (level) == 0))

/*
* Calculate max processes count.
*
Expand Down Expand Up @@ -185,6 +214,14 @@ shmem_int_guc_check_hook(int *newval, void **extra, GucSource source)
return true;
}

static bool
shmem_enum_guc_check_hook(int *newval, void **extra, GucSource source)
{
if (UsedShmemSegAddr == NULL)
return false;
return true;
}

static bool
shmem_bool_guc_check_hook(bool *newval, void **extra, GucSource source)
{
Expand Down Expand Up @@ -260,8 +297,8 @@ setup_gucs()
else if (!strcmp(name, "pg_wait_sampling.profile_queries"))
{
profile_queries_found = true;
var->_bool.variable = &pgws_collector_hdr->profileQueries;
pgws_collector_hdr->profileQueries = true;
var->_enum.variable = &pgws_collector_hdr->profileQueries;
pgws_collector_hdr->profileQueries = PGWS_PROFILE_QUERIES_TOP;
}
else if (!strcmp(name, "pg_wait_sampling.sample_cpu"))
{
Expand Down Expand Up @@ -296,10 +333,10 @@ setup_gucs()
PGC_SUSET, 0, shmem_bool_guc_check_hook, NULL, NULL);

if (!profile_queries_found)
DefineCustomBoolVariable("pg_wait_sampling.profile_queries",
DefineCustomEnumVariable("pg_wait_sampling.profile_queries",
"Sets whether profile should be collected per query.", NULL,
&pgws_collector_hdr->profileQueries, true,
PGC_SUSET, 0, shmem_bool_guc_check_hook, NULL, NULL);
&pgws_collector_hdr->profileQueries, PGWS_PROFILE_QUERIES_TOP, pgws_profile_queries_options,
PGC_SUSET, 0, shmem_enum_guc_check_hook, NULL, NULL);

if (!sample_cpu_found)
DefineCustomBoolVariable("pg_wait_sampling.sample_cpu",
Expand Down Expand Up @@ -354,6 +391,8 @@ pgws_shmem_startup(void)

pgws_collector_hdr = shm_toc_allocate(toc, sizeof(CollectorShmqHeader));
shm_toc_insert(toc, 0, pgws_collector_hdr);
/* needed to please check_GUC_init */
pgws_collector_hdr->profileQueries = PGWS_PROFILE_QUERIES_TOP;
pgws_collector_mq = shm_toc_allocate(toc, COLLECTOR_QUEUE_SIZE);
shm_toc_insert(toc, 1, pgws_collector_mq);
pgws_proc_queryids = shm_toc_allocate(toc,
Expand Down Expand Up @@ -933,10 +972,15 @@ pgws_planner_hook(Query *parse,
int cursorOptions,
ParamListInfo boundParams)
{
PlannedStmt *result;
int i = MyProc - ProcGlobal->allProcs;
if (nesting_level == 0)
PlannedStmt *result;
int i = MyProc - ProcGlobal->allProcs;
uint64 save_queryId = 0;

if (pgws_enabled(nesting_level))
{
save_queryId = pgws_proc_queryids[i];
pgws_proc_queryids[i] = parse->queryId;
}

nesting_level++;
PG_TRY();
Expand All @@ -957,12 +1001,16 @@ pgws_planner_hook(Query *parse,
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else if (pgws_enabled(nesting_level))
pgws_proc_queryids[i] = save_queryId;
}
PG_CATCH();
{
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else if (pgws_enabled(nesting_level))
pgws_proc_queryids[i] = save_queryId;
PG_RE_THROW();
}
PG_END_TRY();
Expand All @@ -977,9 +1025,8 @@ static void
pgws_ExecutorStart(QueryDesc *queryDesc, int eflags)
{
int i = MyProc - ProcGlobal->allProcs;
if (nesting_level == 0)
if (pgws_enabled(nesting_level))
pgws_proc_queryids[i] = queryDesc->plannedstmt->queryId;

if (prev_ExecutorStart)
prev_ExecutorStart(queryDesc, eflags);
else
Expand All @@ -991,6 +1038,9 @@ pgws_ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction,
uint64 count, bool execute_once)
{
int i = MyProc - ProcGlobal->allProcs;
uint64 save_queryId = pgws_proc_queryids[i];

nesting_level++;
PG_TRY();
{
Expand All @@ -999,10 +1049,18 @@ pgws_ExecutorRun(QueryDesc *queryDesc,
else
standard_ExecutorRun(queryDesc, direction, count, execute_once);
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else
pgws_proc_queryids[i] = save_queryId;
}
PG_CATCH();
{
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else
pgws_proc_queryids[i] = save_queryId;
PG_RE_THROW();
}
PG_END_TRY();
Expand All @@ -1011,6 +1069,9 @@ pgws_ExecutorRun(QueryDesc *queryDesc,
static void
pgws_ExecutorFinish(QueryDesc *queryDesc)
{
int i = MyProc - ProcGlobal->allProcs;
uint64 save_queryId = pgws_proc_queryids[i];

nesting_level++;
PG_TRY();
{
Expand All @@ -1019,10 +1080,15 @@ pgws_ExecutorFinish(QueryDesc *queryDesc)
else
standard_ExecutorFinish(queryDesc);
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else
pgws_proc_queryids[i] = save_queryId;
}
PG_CATCH();
{
nesting_level--;
pgws_proc_queryids[i] = save_queryId;
PG_RE_THROW();
}
PG_END_TRY();
Expand Down Expand Up @@ -1061,10 +1127,14 @@ pgws_ProcessUtility(PlannedStmt *pstmt,
#endif
)
{
int i = MyProc - ProcGlobal->allProcs;
int i = MyProc - ProcGlobal->allProcs;
uint64 save_queryId = 0;

if (nesting_level == 0)
if (pgws_enabled(nesting_level))
{
save_queryId = pgws_proc_queryids[i];
pgws_proc_queryids[i] = pstmt->queryId;
}

nesting_level++;
PG_TRY();
Expand Down Expand Up @@ -1098,12 +1168,16 @@ pgws_ProcessUtility(PlannedStmt *pstmt,
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else if (pgws_enabled(nesting_level))
pgws_proc_queryids[i] = save_queryId;
}
PG_CATCH();
{
nesting_level--;
if (nesting_level == 0)
pgws_proc_queryids[i] = UINT64CONST(0);
else if (pgws_enabled(nesting_level))
pgws_proc_queryids[i] = save_queryId;
PG_RE_THROW();
}
PG_END_TRY();
Expand Down
2 changes: 1 addition & 1 deletion pg_wait_sampling.h
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Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,7 @@ typedef struct
int historyPeriod;
int profilePeriod;
bool profilePid;
bool profileQueries;
int profileQueries;
bool sampleCpu;
} CollectorShmqHeader;

Expand Down