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c7ea3f42291bf5c74be8f957c775c5e7b3f78592
postgres/contrib/pg_stat_statements/pg_stat_statements.c
Nathan Bossart 3b42bdb471 Use new overflow-safe integer comparison functions. 
Commit 6b80394781 introduced integer comparison functions designed
to be as efficient as possible while avoiding overflow.  This
commit makes use of these functions in many of the in-tree qsort()
comparators to help ensure transitivity.  Many of these comparator
functions should also see a small performance boost.

Author: Mats Kindahl
Reviewed-by: Andres Freund, Fabrízio de Royes Mello
Discussion: https://postgr.es/m/CA%2B14426g2Wa9QuUpmakwPxXFWG_1FaY0AsApkvcTBy-YfS6uaw%40mail.gmail.com
2024-02-16 14:05:36 -06:00

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/*-------------------------------------------------------------------------
*
* pg_stat_statements.c
* Track statement planning and execution times as well as resource
* usage across a whole database cluster.
*
* Execution costs are totaled for each distinct source query, and kept in
* a shared hashtable. (We track only as many distinct queries as will fit
* in the designated amount of shared memory.)
*
* Starting in Postgres 9.2, this module normalized query entries. As of
* Postgres 14, the normalization is done by the core if compute_query_id is
* enabled, or optionally by third-party modules.
*
* To facilitate presenting entries to users, we create "representative" query
* strings in which constants are replaced with parameter symbols ($n), to
* make it clearer what a normalized entry can represent. To save on shared
* memory, and to avoid having to truncate oversized query strings, we store
* these strings in a temporary external query-texts file. Offsets into this
* file are kept in shared memory.
*
* Note about locking issues: to create or delete an entry in the shared
* hashtable, one must hold pgss->lock exclusively. Modifying any field
* in an entry except the counters requires the same. To look up an entry,
* one must hold the lock shared. To read or update the counters within
* an entry, one must hold the lock shared or exclusive (so the entry doesn't
* disappear!) and also take the entry's mutex spinlock.
* The shared state variable pgss->extent (the next free spot in the external
* query-text file) should be accessed only while holding either the
* pgss->mutex spinlock, or exclusive lock on pgss->lock. We use the mutex to
* allow reserving file space while holding only shared lock on pgss->lock.
* Rewriting the entire external query-text file, eg for garbage collection,
* requires holding pgss->lock exclusively; this allows individual entries
* in the file to be read or written while holding only shared lock.
*
*
* Copyright (c) 2008-2024, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/pg_stat_statements/pg_stat_statements.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <math.h>
#include <sys/stat.h>
#include <unistd.h>
#include "access/parallel.h"
#include "catalog/pg_authid.h"
#include "common/hashfn.h"
#include "common/int.h"
#include "executor/instrument.h"
#include "funcapi.h"
#include "jit/jit.h"
#include "mb/pg_wchar.h"
#include "miscadmin.h"
#include "nodes/queryjumble.h"
#include "optimizer/planner.h"
#include "parser/analyze.h"
#include "parser/parsetree.h"
#include "parser/scanner.h"
#include "parser/scansup.h"
#include "pgstat.h"
#include "storage/fd.h"
#include "storage/ipc.h"
#include "storage/lwlock.h"
#include "storage/shmem.h"
#include "storage/spin.h"
#include "tcop/utility.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/memutils.h"
#include "utils/timestamp.h"
PG_MODULE_MAGIC;
/* Location of permanent stats file (valid when database is shut down) */
#define PGSS_DUMP_FILE PGSTAT_STAT_PERMANENT_DIRECTORY "/pg_stat_statements.stat"
/*
* Location of external query text file.
*/
#define PGSS_TEXT_FILE PG_STAT_TMP_DIR "/pgss_query_texts.stat"
/* Magic number identifying the stats file format */
static const uint32 PGSS_FILE_HEADER = 0x20220408;
/* PostgreSQL major version number, changes in which invalidate all entries */
static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100;
/* XXX: Should USAGE_EXEC reflect execution time and/or buffer usage? */
#define USAGE_EXEC(duration) (1.0)
#define USAGE_INIT (1.0) /* including initial planning */
#define ASSUMED_MEDIAN_INIT (10.0) /* initial assumed median usage */
#define ASSUMED_LENGTH_INIT 1024 /* initial assumed mean query length */
#define USAGE_DECREASE_FACTOR (0.99) /* decreased every entry_dealloc */
#define STICKY_DECREASE_FACTOR (0.50) /* factor for sticky entries */
#define USAGE_DEALLOC_PERCENT 5 /* free this % of entries at once */
#define IS_STICKY(c) ((c.calls[PGSS_PLAN] + c.calls[PGSS_EXEC]) == 0)
/*
* Extension version number, for supporting older extension versions' objects
*/
typedef enum pgssVersion
{
PGSS_V1_0 = 0,
PGSS_V1_1,
PGSS_V1_2,
PGSS_V1_3,
PGSS_V1_8,
PGSS_V1_9,
PGSS_V1_10,
PGSS_V1_11,
} pgssVersion;
typedef enum pgssStoreKind
{
PGSS_INVALID = -1,
/*
* PGSS_PLAN and PGSS_EXEC must be respectively 0 and 1 as they're used to
* reference the underlying values in the arrays in the Counters struct,
* and this order is required in pg_stat_statements_internal().
*/
PGSS_PLAN = 0,
PGSS_EXEC,
PGSS_NUMKIND /* Must be last value of this enum */
} pgssStoreKind;
/*
* Hashtable key that defines the identity of a hashtable entry. We separate
* queries by user and by database even if they are otherwise identical.
*
* If you add a new key to this struct, make sure to teach pgss_store() to
* zero the padding bytes. Otherwise, things will break, because pgss_hash is
* created using HASH_BLOBS, and thus tag_hash is used to hash this.
*/
typedef struct pgssHashKey
{
Oid userid; /* user OID */
Oid dbid; /* database OID */
uint64 queryid; /* query identifier */
bool toplevel; /* query executed at top level */
} pgssHashKey;
/*
* The actual stats counters kept within pgssEntry.
*/
typedef struct Counters
{
int64 calls[PGSS_NUMKIND]; /* # of times planned/executed */
double total_time[PGSS_NUMKIND]; /* total planning/execution time,
* in msec */
double min_time[PGSS_NUMKIND]; /* minimum planning/execution time in
* msec since min/max reset */
double max_time[PGSS_NUMKIND]; /* maximum planning/execution time in
* msec since min/max reset */
double mean_time[PGSS_NUMKIND]; /* mean planning/execution time in
* msec */
double sum_var_time[PGSS_NUMKIND]; /* sum of variances in
* planning/execution time in msec */
int64 rows; /* total # of retrieved or affected rows */
int64 shared_blks_hit; /* # of shared buffer hits */
int64 shared_blks_read; /* # of shared disk blocks read */
int64 shared_blks_dirtied; /* # of shared disk blocks dirtied */
int64 shared_blks_written; /* # of shared disk blocks written */
int64 local_blks_hit; /* # of local buffer hits */
int64 local_blks_read; /* # of local disk blocks read */
int64 local_blks_dirtied; /* # of local disk blocks dirtied */
int64 local_blks_written; /* # of local disk blocks written */
int64 temp_blks_read; /* # of temp blocks read */
int64 temp_blks_written; /* # of temp blocks written */
double shared_blk_read_time; /* time spent reading shared blocks,
* in msec */
double shared_blk_write_time; /* time spent writing shared blocks,
* in msec */
double local_blk_read_time; /* time spent reading local blocks, in
* msec */
double local_blk_write_time; /* time spent writing local blocks, in
* msec */
double temp_blk_read_time; /* time spent reading temp blocks, in msec */
double temp_blk_write_time; /* time spent writing temp blocks, in
* msec */
double usage; /* usage factor */
int64 wal_records; /* # of WAL records generated */
int64 wal_fpi; /* # of WAL full page images generated */
uint64 wal_bytes; /* total amount of WAL generated in bytes */
int64 jit_functions; /* total number of JIT functions emitted */
double jit_generation_time; /* total time to generate jit code */
int64 jit_inlining_count; /* number of times inlining time has been
* > 0 */
double jit_deform_time; /* total time to deform tuples in jit code */
int64 jit_deform_count; /* number of times deform time has been >
* 0 */
double jit_inlining_time; /* total time to inline jit code */
int64 jit_optimization_count; /* number of times optimization time
* has been > 0 */
double jit_optimization_time; /* total time to optimize jit code */
int64 jit_emission_count; /* number of times emission time has been
* > 0 */
double jit_emission_time; /* total time to emit jit code */
} Counters;
/*
* Global statistics for pg_stat_statements
*/
typedef struct pgssGlobalStats
{
int64 dealloc; /* # of times entries were deallocated */
TimestampTz stats_reset; /* timestamp with all stats reset */
} pgssGlobalStats;
/*
* Statistics per statement
*
* Note: in event of a failure in garbage collection of the query text file,
* we reset query_offset to zero and query_len to -1. This will be seen as
* an invalid state by qtext_fetch().
*/
typedef struct pgssEntry
{
pgssHashKey key; /* hash key of entry - MUST BE FIRST */
Counters counters; /* the statistics for this query */
Size query_offset; /* query text offset in external file */
int query_len; /* # of valid bytes in query string, or -1 */
int encoding; /* query text encoding */
TimestampTz stats_since; /* timestamp of entry allocation */
TimestampTz minmax_stats_since; /* timestamp of last min/max values reset */
slock_t mutex; /* protects the counters only */
} pgssEntry;
/*
* Global shared state
*/
typedef struct pgssSharedState
{
LWLock *lock; /* protects hashtable search/modification */
double cur_median_usage; /* current median usage in hashtable */
Size mean_query_len; /* current mean entry text length */
slock_t mutex; /* protects following fields only: */
Size extent; /* current extent of query file */
int n_writers; /* number of active writers to query file */
int gc_count; /* query file garbage collection cycle count */
pgssGlobalStats stats; /* global statistics for pgss */
} pgssSharedState;
/*---- Local variables ----*/
/* Current nesting depth of planner/ExecutorRun/ProcessUtility calls */
static int nesting_level = 0;
/* Saved hook values in case of unload */
static shmem_request_hook_type prev_shmem_request_hook = NULL;
static shmem_startup_hook_type prev_shmem_startup_hook = NULL;
static post_parse_analyze_hook_type prev_post_parse_analyze_hook = NULL;
static planner_hook_type prev_planner_hook = NULL;
static ExecutorStart_hook_type prev_ExecutorStart = NULL;
static ExecutorRun_hook_type prev_ExecutorRun = NULL;
static ExecutorFinish_hook_type prev_ExecutorFinish = NULL;
static ExecutorEnd_hook_type prev_ExecutorEnd = NULL;
static ProcessUtility_hook_type prev_ProcessUtility = NULL;
/* Links to shared memory state */
static pgssSharedState *pgss = NULL;
static HTAB *pgss_hash = NULL;
/*---- GUC variables ----*/
typedef enum
{
PGSS_TRACK_NONE, /* track no statements */
PGSS_TRACK_TOP, /* only top level statements */
PGSS_TRACK_ALL, /* all statements, including nested ones */
} PGSSTrackLevel;
static const struct config_enum_entry track_options[] =
{
{"none", PGSS_TRACK_NONE, false},
{"top", PGSS_TRACK_TOP, false},
{"all", PGSS_TRACK_ALL, false},
{NULL, 0, false}
};
static int pgss_max = 5000; /* max # statements to track */
static int pgss_track = PGSS_TRACK_TOP; /* tracking level */
static bool pgss_track_utility = true; /* whether to track utility commands */
static bool pgss_track_planning = false; /* whether to track planning
* duration */
static bool pgss_save = true; /* whether to save stats across shutdown */
#define pgss_enabled(level) \
(!IsParallelWorker() && \
(pgss_track == PGSS_TRACK_ALL || \
(pgss_track == PGSS_TRACK_TOP && (level) == 0)))
#define record_gc_qtexts() \
do { \
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss; \
SpinLockAcquire(&s->mutex); \
s->gc_count++; \
SpinLockRelease(&s->mutex); \
} while(0)
/*---- Function declarations ----*/
PG_FUNCTION_INFO_V1(pg_stat_statements_reset);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset_1_7);
PG_FUNCTION_INFO_V1(pg_stat_statements_reset_1_11);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_2);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_3);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_8);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_9);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_10);
PG_FUNCTION_INFO_V1(pg_stat_statements_1_11);
PG_FUNCTION_INFO_V1(pg_stat_statements);
PG_FUNCTION_INFO_V1(pg_stat_statements_info);
static void pgss_shmem_request(void);
static void pgss_shmem_startup(void);
static void pgss_shmem_shutdown(int code, Datum arg);
static void pgss_post_parse_analyze(ParseState *pstate, Query *query,
JumbleState *jstate);
static PlannedStmt *pgss_planner(Query *parse,
const char *query_string,
int cursorOptions,
ParamListInfo boundParams);
static void pgss_ExecutorStart(QueryDesc *queryDesc, int eflags);
static void pgss_ExecutorRun(QueryDesc *queryDesc,
ScanDirection direction,
uint64 count, bool execute_once);
static void pgss_ExecutorFinish(QueryDesc *queryDesc);
static void pgss_ExecutorEnd(QueryDesc *queryDesc);
static void pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
bool readOnlyTree,
ProcessUtilityContext context, ParamListInfo params,
QueryEnvironment *queryEnv,
DestReceiver *dest, QueryCompletion *qc);
static void pgss_store(const char *query, uint64 queryId,
int query_location, int query_len,
pgssStoreKind kind,
double total_time, uint64 rows,
const BufferUsage *bufusage,
const WalUsage *walusage,
const struct JitInstrumentation *jitusage,
JumbleState *jstate);
static void pg_stat_statements_internal(FunctionCallInfo fcinfo,
pgssVersion api_version,
bool showtext);
static Size pgss_memsize(void);
static pgssEntry *entry_alloc(pgssHashKey *key, Size query_offset, int query_len,
int encoding, bool sticky);
static void entry_dealloc(void);
static bool qtext_store(const char *query, int query_len,
Size *query_offset, int *gc_count);
static char *qtext_load_file(Size *buffer_size);
static char *qtext_fetch(Size query_offset, int query_len,
char *buffer, Size buffer_size);
static bool need_gc_qtexts(void);
static void gc_qtexts(void);
static TimestampTz entry_reset(Oid userid, Oid dbid, uint64 queryid, bool minmax_only);
static char *generate_normalized_query(JumbleState *jstate, const char *query,
int query_loc, int *query_len_p);
static void fill_in_constant_lengths(JumbleState *jstate, const char *query,
int query_loc);
static int comp_location(const void *a, const void *b);
/*
* Module load callback
*/
void
_PG_init(void)
{
/*
* In order to create our shared memory area, we have to be loaded via
* shared_preload_libraries. If not, fall out without hooking into any of
* the main system. (We don't throw error here because it seems useful to
* allow the pg_stat_statements functions to be created even when the
* module isn't active. The functions must protect themselves against
* being called then, however.)
*/
if (!process_shared_preload_libraries_in_progress)
return;
/*
* Inform the postmaster that we want to enable query_id calculation if
* compute_query_id is set to auto.
*/
EnableQueryId();
/*
* Define (or redefine) custom GUC variables.
*/
DefineCustomIntVariable("pg_stat_statements.max",
"Sets the maximum number of statements tracked by pg_stat_statements.",
NULL,
&pgss_max,
5000,
100,
INT_MAX / 2,
PGC_POSTMASTER,
0,
NULL,
NULL,
NULL);
DefineCustomEnumVariable("pg_stat_statements.track",
"Selects which statements are tracked by pg_stat_statements.",
NULL,
&pgss_track,
PGSS_TRACK_TOP,
track_options,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_stat_statements.track_utility",
"Selects whether utility commands are tracked by pg_stat_statements.",
NULL,
&pgss_track_utility,
true,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_stat_statements.track_planning",
"Selects whether planning duration is tracked by pg_stat_statements.",
NULL,
&pgss_track_planning,
false,
PGC_SUSET,
0,
NULL,
NULL,
NULL);
DefineCustomBoolVariable("pg_stat_statements.save",
"Save pg_stat_statements statistics across server shutdowns.",
NULL,
&pgss_save,
true,
PGC_SIGHUP,
0,
NULL,
NULL,
NULL);
MarkGUCPrefixReserved("pg_stat_statements");
/*
* Install hooks.
*/
prev_shmem_request_hook = shmem_request_hook;
shmem_request_hook = pgss_shmem_request;
prev_shmem_startup_hook = shmem_startup_hook;
shmem_startup_hook = pgss_shmem_startup;
prev_post_parse_analyze_hook = post_parse_analyze_hook;
post_parse_analyze_hook = pgss_post_parse_analyze;
prev_planner_hook = planner_hook;
planner_hook = pgss_planner;
prev_ExecutorStart = ExecutorStart_hook;
ExecutorStart_hook = pgss_ExecutorStart;
prev_ExecutorRun = ExecutorRun_hook;
ExecutorRun_hook = pgss_ExecutorRun;
prev_ExecutorFinish = ExecutorFinish_hook;
ExecutorFinish_hook = pgss_ExecutorFinish;
prev_ExecutorEnd = ExecutorEnd_hook;
ExecutorEnd_hook = pgss_ExecutorEnd;
prev_ProcessUtility = ProcessUtility_hook;
ProcessUtility_hook = pgss_ProcessUtility;
}
/*
* shmem_request hook: request additional shared resources. We'll allocate or
* attach to the shared resources in pgss_shmem_startup().
*/
static void
pgss_shmem_request(void)
{
if (prev_shmem_request_hook)
prev_shmem_request_hook();
RequestAddinShmemSpace(pgss_memsize());
RequestNamedLWLockTranche("pg_stat_statements", 1);
}
/*
* shmem_startup hook: allocate or attach to shared memory,
* then load any pre-existing statistics from file.
* Also create and load the query-texts file, which is expected to exist
* (even if empty) while the module is enabled.
*/
static void
pgss_shmem_startup(void)
{
bool found;
HASHCTL info;
FILE *file = NULL;
FILE *qfile = NULL;
uint32 header;
int32 num;
int32 pgver;
int32 i;
int buffer_size;
char *buffer = NULL;
if (prev_shmem_startup_hook)
prev_shmem_startup_hook();
/* reset in case this is a restart within the postmaster */
pgss = NULL;
pgss_hash = NULL;
/*
* Create or attach to the shared memory state, including hash table
*/
LWLockAcquire(AddinShmemInitLock, LW_EXCLUSIVE);
pgss = ShmemInitStruct("pg_stat_statements",
sizeof(pgssSharedState),
&found);
if (!found)
{
/* First time through ... */
pgss->lock = &(GetNamedLWLockTranche("pg_stat_statements"))->lock;
pgss->cur_median_usage = ASSUMED_MEDIAN_INIT;
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
SpinLockInit(&pgss->mutex);
pgss->extent = 0;
pgss->n_writers = 0;
pgss->gc_count = 0;
pgss->stats.dealloc = 0;
pgss->stats.stats_reset = GetCurrentTimestamp();
}
info.keysize = sizeof(pgssHashKey);
info.entrysize = sizeof(pgssEntry);
pgss_hash = ShmemInitHash("pg_stat_statements hash",
pgss_max, pgss_max,
&info,
HASH_ELEM | HASH_BLOBS);
LWLockRelease(AddinShmemInitLock);
/*
* If we're in the postmaster (or a standalone backend...), set up a shmem
* exit hook to dump the statistics to disk.
*/
if (!IsUnderPostmaster)
on_shmem_exit(pgss_shmem_shutdown, (Datum) 0);
/*
* Done if some other process already completed our initialization.
*/
if (found)
return;
/*
* Note: we don't bother with locks here, because there should be no other
* processes running when this code is reached.
*/
/* Unlink query text file possibly left over from crash */
unlink(PGSS_TEXT_FILE);
/* Allocate new query text temp file */
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
goto write_error;
/*
* If we were told not to load old statistics, we're done. (Note we do
* not try to unlink any old dump file in this case. This seems a bit
* questionable but it's the historical behavior.)
*/
if (!pgss_save)
{
FreeFile(qfile);
return;
}
/*
* Attempt to load old statistics from the dump file.
*/
file = AllocateFile(PGSS_DUMP_FILE, PG_BINARY_R);
if (file == NULL)
{
if (errno != ENOENT)
goto read_error;
/* No existing persisted stats file, so we're done */
FreeFile(qfile);
return;
}
buffer_size = 2048;
buffer = (char *) palloc(buffer_size);
if (fread(&header, sizeof(uint32), 1, file) != 1 ||
fread(&pgver, sizeof(uint32), 1, file) != 1 ||
fread(&num, sizeof(int32), 1, file) != 1)
goto read_error;
if (header != PGSS_FILE_HEADER ||
pgver != PGSS_PG_MAJOR_VERSION)
goto data_error;
for (i = 0; i < num; i++)
{
pgssEntry temp;
pgssEntry *entry;
Size query_offset;
if (fread(&temp, sizeof(pgssEntry), 1, file) != 1)
goto read_error;
/* Encoding is the only field we can easily sanity-check */
if (!PG_VALID_BE_ENCODING(temp.encoding))
goto data_error;
/* Resize buffer as needed */
if (temp.query_len >= buffer_size)
{
buffer_size = Max(buffer_size * 2, temp.query_len + 1);
buffer = repalloc(buffer, buffer_size);
}
if (fread(buffer, 1, temp.query_len + 1, file) != temp.query_len + 1)
goto read_error;
/* Should have a trailing null, but let's make sure */
buffer[temp.query_len] = '\0';
/* Skip loading "sticky" entries */
if (IS_STICKY(temp.counters))
continue;
/* Store the query text */
query_offset = pgss->extent;
if (fwrite(buffer, 1, temp.query_len + 1, qfile) != temp.query_len + 1)
goto write_error;
pgss->extent += temp.query_len + 1;
/* make the hashtable entry (discards old entries if too many) */
entry = entry_alloc(&temp.key, query_offset, temp.query_len,
temp.encoding,
false);
/* copy in the actual stats */
entry->counters = temp.counters;
entry->stats_since = temp.stats_since;
entry->minmax_stats_since = temp.minmax_stats_since;
}
/* Read global statistics for pg_stat_statements */
if (fread(&pgss->stats, sizeof(pgssGlobalStats), 1, file) != 1)
goto read_error;
pfree(buffer);
FreeFile(file);
FreeFile(qfile);
/*
* Remove the persisted stats file so it's not included in
* backups/replication standbys, etc. A new file will be written on next
* shutdown.
*
* Note: it's okay if the PGSS_TEXT_FILE is included in a basebackup,
* because we remove that file on startup; it acts inversely to
* PGSS_DUMP_FILE, in that it is only supposed to be around when the
* server is running, whereas PGSS_DUMP_FILE is only supposed to be around
* when the server is not running. Leaving the file creates no danger of
* a newly restored database having a spurious record of execution costs,
* which is what we're really concerned about here.
*/
unlink(PGSS_DUMP_FILE);
return;
read_error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
PGSS_DUMP_FILE)));
goto fail;
data_error:
ereport(LOG,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("ignoring invalid data in file \"%s\"",
PGSS_DUMP_FILE)));
goto fail;
write_error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
fail:
if (buffer)
pfree(buffer);
if (file)
FreeFile(file);
if (qfile)
FreeFile(qfile);
/* If possible, throw away the bogus file; ignore any error */
unlink(PGSS_DUMP_FILE);
/*
* Don't unlink PGSS_TEXT_FILE here; it should always be around while the
* server is running with pg_stat_statements enabled
*/
}
/*
* shmem_shutdown hook: Dump statistics into file.
*
* Note: we don't bother with acquiring lock, because there should be no
* other processes running when this is called.
*/
static void
pgss_shmem_shutdown(int code, Datum arg)
{
FILE *file;
char *qbuffer = NULL;
Size qbuffer_size = 0;
HASH_SEQ_STATUS hash_seq;
int32 num_entries;
pgssEntry *entry;
/* Don't try to dump during a crash. */
if (code)
return;
/* Safety check ... shouldn't get here unless shmem is set up. */
if (!pgss || !pgss_hash)
return;
/* Don't dump if told not to. */
if (!pgss_save)
return;
file = AllocateFile(PGSS_DUMP_FILE ".tmp", PG_BINARY_W);
if (file == NULL)
goto error;
if (fwrite(&PGSS_FILE_HEADER, sizeof(uint32), 1, file) != 1)
goto error;
if (fwrite(&PGSS_PG_MAJOR_VERSION, sizeof(uint32), 1, file) != 1)
goto error;
num_entries = hash_get_num_entries(pgss_hash);
if (fwrite(&num_entries, sizeof(int32), 1, file) != 1)
goto error;
qbuffer = qtext_load_file(&qbuffer_size);
if (qbuffer == NULL)
goto error;
/*
* When serializing to disk, we store query texts immediately after their
* entry data. Any orphaned query texts are thereby excluded.
*/
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
int len = entry->query_len;
char *qstr = qtext_fetch(entry->query_offset, len,
qbuffer, qbuffer_size);
if (qstr == NULL)
continue; /* Ignore any entries with bogus texts */
if (fwrite(entry, sizeof(pgssEntry), 1, file) != 1 ||
fwrite(qstr, 1, len + 1, file) != len + 1)
{
/* note: we assume hash_seq_term won't change errno */
hash_seq_term(&hash_seq);
goto error;
}
}
/* Dump global statistics for pg_stat_statements */
if (fwrite(&pgss->stats, sizeof(pgssGlobalStats), 1, file) != 1)
goto error;
free(qbuffer);
qbuffer = NULL;
if (FreeFile(file))
{
file = NULL;
goto error;
}
/*
* Rename file into place, so we atomically replace any old one.
*/
(void) durable_rename(PGSS_DUMP_FILE ".tmp", PGSS_DUMP_FILE, LOG);
/* Unlink query-texts file; it's not needed while shutdown */
unlink(PGSS_TEXT_FILE);
return;
error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_DUMP_FILE ".tmp")));
free(qbuffer);
if (file)
FreeFile(file);
unlink(PGSS_DUMP_FILE ".tmp");
unlink(PGSS_TEXT_FILE);
}
/*
* Post-parse-analysis hook: mark query with a queryId
*/
static void
pgss_post_parse_analyze(ParseState *pstate, Query *query, JumbleState *jstate)
{
if (prev_post_parse_analyze_hook)
prev_post_parse_analyze_hook(pstate, query, jstate);
/* Safety check... */
if (!pgss || !pgss_hash || !pgss_enabled(nesting_level))
return;
/*
* If it's EXECUTE, clear the queryId so that stats will accumulate for
* the underlying PREPARE. But don't do this if we're not tracking
* utility statements, to avoid messing up another extension that might be
* tracking them.
*/
if (query->utilityStmt)
{
if (pgss_track_utility && IsA(query->utilityStmt, ExecuteStmt))
{
query->queryId = UINT64CONST(0);
return;
}
}
/*
* If query jumbling were able to identify any ignorable constants, we
* immediately create a hash table entry for the query, so that we can
* record the normalized form of the query string. If there were no such
* constants, the normalized string would be the same as the query text
* anyway, so there's no need for an early entry.
*/
if (jstate && jstate->clocations_count > 0)
pgss_store(pstate->p_sourcetext,
query->queryId,
query->stmt_location,
query->stmt_len,
PGSS_INVALID,
0,
0,
NULL,
NULL,
NULL,
jstate);
}
/*
* Planner hook: forward to regular planner, but measure planning time
* if needed.
*/
static PlannedStmt *
pgss_planner(Query *parse,
const char *query_string,
int cursorOptions,
ParamListInfo boundParams)
{
PlannedStmt *result;
/*
* We can't process the query if no query_string is provided, as
* pgss_store needs it. We also ignore query without queryid, as it would
* be treated as a utility statement, which may not be the case.
*
* Note that planner_hook can be called from the planner itself, so we
* have a specific nesting level for the planner. However, utility
* commands containing optimizable statements can also call the planner,
* same for regular DML (for instance for underlying foreign key queries).
* So testing the planner nesting level only is not enough to detect real
* top level planner call.
*/
if (pgss_enabled(nesting_level)
&& pgss_track_planning && query_string
&& parse->queryId != UINT64CONST(0))
{
instr_time start;
instr_time duration;
BufferUsage bufusage_start,
bufusage;
WalUsage walusage_start,
walusage;
/* We need to track buffer usage as the planner can access them. */
bufusage_start = pgBufferUsage;
/*
* Similarly the planner could write some WAL records in some cases
* (e.g. setting a hint bit with those being WAL-logged)
*/
walusage_start = pgWalUsage;
INSTR_TIME_SET_CURRENT(start);
nesting_level++;
PG_TRY();
{
if (prev_planner_hook)
result = prev_planner_hook(parse, query_string, cursorOptions,
boundParams);
else
result = standard_planner(parse, query_string, cursorOptions,
boundParams);
}
PG_FINALLY();
{
nesting_level--;
}
PG_END_TRY();
INSTR_TIME_SET_CURRENT(duration);
INSTR_TIME_SUBTRACT(duration, start);
/* calc differences of buffer counters. */
memset(&bufusage, 0, sizeof(BufferUsage));
BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
/* calc differences of WAL counters. */
memset(&walusage, 0, sizeof(WalUsage));
WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
pgss_store(query_string,
parse->queryId,
parse->stmt_location,
parse->stmt_len,
PGSS_PLAN,
INSTR_TIME_GET_MILLISEC(duration),
0,
&bufusage,
&walusage,
NULL,
NULL);
}
else
{
/*
* Even though we're not tracking plan time for this statement, we
* must still increment the nesting level, to ensure that functions
* evaluated during planning are not seen as top-level calls.
*/
nesting_level++;
PG_TRY();
{
if (prev_planner_hook)
result = prev_planner_hook(parse, query_string, cursorOptions,
boundParams);
else
result = standard_planner(parse, query_string, cursorOptions,
boundParams);
}
PG_FINALLY();
{
nesting_level--;
}
PG_END_TRY();
}
return result;
}
/*
* ExecutorStart hook: start up tracking if needed
*/
static void
pgss_ExecutorStart(QueryDesc *queryDesc, int eflags)
{
if (prev_ExecutorStart)
prev_ExecutorStart(queryDesc, eflags);
else
standard_ExecutorStart(queryDesc, eflags);
/*
* If query has queryId zero, don't track it. This prevents double
* counting of optimizable statements that are directly contained in
* utility statements.
*/
if (pgss_enabled(nesting_level) && queryDesc->plannedstmt->queryId != UINT64CONST(0))
{
/*
* Set up to track total elapsed time in ExecutorRun. Make sure the
* space is allocated in the per-query context so it will go away at
* ExecutorEnd.
*/
if (queryDesc->totaltime == NULL)
{
MemoryContext oldcxt;
oldcxt = MemoryContextSwitchTo(queryDesc->estate->es_query_cxt);
queryDesc->totaltime = InstrAlloc(1, INSTRUMENT_ALL, false);
MemoryContextSwitchTo(oldcxt);
}
}
}
/*
* ExecutorRun hook: all we need do is track nesting depth
*/
static void
pgss_ExecutorRun(QueryDesc *queryDesc, ScanDirection direction, uint64 count,
bool execute_once)
{
nesting_level++;
PG_TRY();
{
if (prev_ExecutorRun)
prev_ExecutorRun(queryDesc, direction, count, execute_once);
else
standard_ExecutorRun(queryDesc, direction, count, execute_once);
}
PG_FINALLY();
{
nesting_level--;
}
PG_END_TRY();
}
/*
* ExecutorFinish hook: all we need do is track nesting depth
*/
static void
pgss_ExecutorFinish(QueryDesc *queryDesc)
{
nesting_level++;
PG_TRY();
{
if (prev_ExecutorFinish)
prev_ExecutorFinish(queryDesc);
else
standard_ExecutorFinish(queryDesc);
}
PG_FINALLY();
{
nesting_level--;
}
PG_END_TRY();
}
/*
* ExecutorEnd hook: store results if needed
*/
static void
pgss_ExecutorEnd(QueryDesc *queryDesc)
{
uint64 queryId = queryDesc->plannedstmt->queryId;
if (queryId != UINT64CONST(0) && queryDesc->totaltime &&
pgss_enabled(nesting_level))
{
/*
* Make sure stats accumulation is done. (Note: it's okay if several
* levels of hook all do this.)
*/
InstrEndLoop(queryDesc->totaltime);
pgss_store(queryDesc->sourceText,
queryId,
queryDesc->plannedstmt->stmt_location,
queryDesc->plannedstmt->stmt_len,
PGSS_EXEC,
queryDesc->totaltime->total * 1000.0, /* convert to msec */
queryDesc->estate->es_total_processed,
&queryDesc->totaltime->bufusage,
&queryDesc->totaltime->walusage,
queryDesc->estate->es_jit ? &queryDesc->estate->es_jit->instr : NULL,
NULL);
}
if (prev_ExecutorEnd)
prev_ExecutorEnd(queryDesc);
else
standard_ExecutorEnd(queryDesc);
}
/*
* ProcessUtility hook
*/
static void
pgss_ProcessUtility(PlannedStmt *pstmt, const char *queryString,
bool readOnlyTree,
ProcessUtilityContext context,
ParamListInfo params, QueryEnvironment *queryEnv,
DestReceiver *dest, QueryCompletion *qc)
{
Node *parsetree = pstmt->utilityStmt;
uint64 saved_queryId = pstmt->queryId;
int saved_stmt_location = pstmt->stmt_location;
int saved_stmt_len = pstmt->stmt_len;
bool enabled = pgss_track_utility && pgss_enabled(nesting_level);
/*
* Force utility statements to get queryId zero. We do this even in cases
* where the statement contains an optimizable statement for which a
* queryId could be derived (such as EXPLAIN or DECLARE CURSOR). For such
* cases, runtime control will first go through ProcessUtility and then
* the executor, and we don't want the executor hooks to do anything,
* since we are already measuring the statement's costs at the utility
* level.
*
* Note that this is only done if pg_stat_statements is enabled and
* configured to track utility statements, in the unlikely possibility
* that user configured another extension to handle utility statements
* only.
*/
if (enabled)
pstmt->queryId = UINT64CONST(0);
/*
* If it's an EXECUTE statement, we don't track it and don't increment the
* nesting level. This allows the cycles to be charged to the underlying
* PREPARE instead (by the Executor hooks), which is much more useful.
*
* We also don't track execution of PREPARE. If we did, we would get one
* hash table entry for the PREPARE (with hash calculated from the query
* string), and then a different one with the same query string (but hash
* calculated from the query tree) would be used to accumulate costs of
* ensuing EXECUTEs. This would be confusing. Since PREPARE doesn't
* actually run the planner (only parse+rewrite), its costs are generally
* pretty negligible and it seems okay to just ignore it.
*/
if (enabled &&
!IsA(parsetree, ExecuteStmt) &&
!IsA(parsetree, PrepareStmt))
{
instr_time start;
instr_time duration;
uint64 rows;
BufferUsage bufusage_start,
bufusage;
WalUsage walusage_start,
walusage;
bufusage_start = pgBufferUsage;
walusage_start = pgWalUsage;
INSTR_TIME_SET_CURRENT(start);
nesting_level++;
PG_TRY();
{
if (prev_ProcessUtility)
prev_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
else
standard_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
}
PG_FINALLY();
{
nesting_level--;
}
PG_END_TRY();
/*
* CAUTION: do not access the *pstmt data structure again below here.
* If it was a ROLLBACK or similar, that data structure may have been
* freed. We must copy everything we still need into local variables,
* which we did above.
*
* For the same reason, we can't risk restoring pstmt->queryId to its
* former value, which'd otherwise be a good idea.
*/
INSTR_TIME_SET_CURRENT(duration);
INSTR_TIME_SUBTRACT(duration, start);
/*
* Track the total number of rows retrieved or affected by the utility
* statements of COPY, FETCH, CREATE TABLE AS, CREATE MATERIALIZED
* VIEW, REFRESH MATERIALIZED VIEW and SELECT INTO.
*/
rows = (qc && (qc->commandTag == CMDTAG_COPY ||
qc->commandTag == CMDTAG_FETCH ||
qc->commandTag == CMDTAG_SELECT ||
qc->commandTag == CMDTAG_REFRESH_MATERIALIZED_VIEW)) ?
qc->nprocessed : 0;
/* calc differences of buffer counters. */
memset(&bufusage, 0, sizeof(BufferUsage));
BufferUsageAccumDiff(&bufusage, &pgBufferUsage, &bufusage_start);
/* calc differences of WAL counters. */
memset(&walusage, 0, sizeof(WalUsage));
WalUsageAccumDiff(&walusage, &pgWalUsage, &walusage_start);
pgss_store(queryString,
saved_queryId,
saved_stmt_location,
saved_stmt_len,
PGSS_EXEC,
INSTR_TIME_GET_MILLISEC(duration),
rows,
&bufusage,
&walusage,
NULL,
NULL);
}
else
{
/*
* Even though we're not tracking execution time for this statement,
* we must still increment the nesting level, to ensure that functions
* evaluated within it are not seen as top-level calls. But don't do
* so for EXECUTE; that way, when control reaches pgss_planner or
* pgss_ExecutorStart, we will treat the costs as top-level if
* appropriate. Likewise, don't bump for PREPARE, so that parse
* analysis will treat the statement as top-level if appropriate.
*
* To be absolutely certain we don't mess up the nesting level,
* evaluate the bump_level condition just once.
*/
bool bump_level =
!IsA(parsetree, ExecuteStmt) &&
!IsA(parsetree, PrepareStmt);
if (bump_level)
nesting_level++;
PG_TRY();
{
if (prev_ProcessUtility)
prev_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
else
standard_ProcessUtility(pstmt, queryString, readOnlyTree,
context, params, queryEnv,
dest, qc);
}
PG_FINALLY();
{
if (bump_level)
nesting_level--;
}
PG_END_TRY();
}
}
/*
* Store some statistics for a statement.
*
* If jstate is not NULL then we're trying to create an entry for which
* we have no statistics as yet; we just want to record the normalized
* query string. total_time, rows, bufusage and walusage are ignored in this
* case.
*
* If kind is PGSS_PLAN or PGSS_EXEC, its value is used as the array position
* for the arrays in the Counters field.
*/
static void
pgss_store(const char *query, uint64 queryId,
int query_location, int query_len,
pgssStoreKind kind,
double total_time, uint64 rows,
const BufferUsage *bufusage,
const WalUsage *walusage,
const struct JitInstrumentation *jitusage,
JumbleState *jstate)
{
pgssHashKey key;
pgssEntry *entry;
char *norm_query = NULL;
int encoding = GetDatabaseEncoding();
Assert(query != NULL);
/* Safety check... */
if (!pgss || !pgss_hash)
return;
/*
* Nothing to do if compute_query_id isn't enabled and no other module
* computed a query identifier.
*/
if (queryId == UINT64CONST(0))
return;
/*
* Confine our attention to the relevant part of the string, if the query
* is a portion of a multi-statement source string, and update query
* location and length if needed.
*/
query = CleanQuerytext(query, &query_location, &query_len);
/* Set up key for hashtable search */
/* clear padding */
memset(&key, 0, sizeof(pgssHashKey));
key.userid = GetUserId();
key.dbid = MyDatabaseId;
key.queryid = queryId;
key.toplevel = (nesting_level == 0);
/* Lookup the hash table entry with shared lock. */
LWLockAcquire(pgss->lock, LW_SHARED);
entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_FIND, NULL);
/* Create new entry, if not present */
if (!entry)
{
Size query_offset;
int gc_count;
bool stored;
bool do_gc;
/*
* Create a new, normalized query string if caller asked. We don't
* need to hold the lock while doing this work. (Note: in any case,
* it's possible that someone else creates a duplicate hashtable entry
* in the interval where we don't hold the lock below. That case is
* handled by entry_alloc.)
*/
if (jstate)
{
LWLockRelease(pgss->lock);
norm_query = generate_normalized_query(jstate, query,
query_location,
&query_len);
LWLockAcquire(pgss->lock, LW_SHARED);
}
/* Append new query text to file with only shared lock held */
stored = qtext_store(norm_query ? norm_query : query, query_len,
&query_offset, &gc_count);
/*
* Determine whether we need to garbage collect external query texts
* while the shared lock is still held. This micro-optimization
* avoids taking the time to decide this while holding exclusive lock.
*/
do_gc = need_gc_qtexts();
/* Need exclusive lock to make a new hashtable entry - promote */
LWLockRelease(pgss->lock);
LWLockAcquire(pgss->lock, LW_EXCLUSIVE);
/*
* A garbage collection may have occurred while we weren't holding the
* lock. In the unlikely event that this happens, the query text we
* stored above will have been garbage collected, so write it again.
* This should be infrequent enough that doing it while holding
* exclusive lock isn't a performance problem.
*/
if (!stored || pgss->gc_count != gc_count)
stored = qtext_store(norm_query ? norm_query : query, query_len,
&query_offset, NULL);
/* If we failed to write to the text file, give up */
if (!stored)
goto done;
/* OK to create a new hashtable entry */
entry = entry_alloc(&key, query_offset, query_len, encoding,
jstate != NULL);
/* If needed, perform garbage collection while exclusive lock held */
if (do_gc)
gc_qtexts();
}
/* Increment the counts, except when jstate is not NULL */
if (!jstate)
{
/*
* Grab the spinlock while updating the counters (see comment about
* locking rules at the head of the file)
*/
volatile pgssEntry *e = (volatile pgssEntry *) entry;
Assert(kind == PGSS_PLAN || kind == PGSS_EXEC);
SpinLockAcquire(&e->mutex);
/* "Unstick" entry if it was previously sticky */
if (IS_STICKY(e->counters))
e->counters.usage = USAGE_INIT;
e->counters.calls[kind] += 1;
e->counters.total_time[kind] += total_time;
if (e->counters.calls[kind] == 1)
{
e->counters.min_time[kind] = total_time;
e->counters.max_time[kind] = total_time;
e->counters.mean_time[kind] = total_time;
}
else
{
/*
* Welford's method for accurately computing variance. See
* <http://www.johndcook.com/blog/standard_deviation/>
*/
double old_mean = e->counters.mean_time[kind];
e->counters.mean_time[kind] +=
(total_time - old_mean) / e->counters.calls[kind];
e->counters.sum_var_time[kind] +=
(total_time - old_mean) * (total_time - e->counters.mean_time[kind]);
/*
* Calculate min and max time. min = 0 and max = 0 means that the
* min/max statistics were reset
*/
if (e->counters.min_time[kind] == 0
&& e->counters.max_time[kind] == 0)
{
e->counters.min_time[kind] = total_time;
e->counters.max_time[kind] = total_time;
}
else
{
if (e->counters.min_time[kind] > total_time)
e->counters.min_time[kind] = total_time;
if (e->counters.max_time[kind] < total_time)
e->counters.max_time[kind] = total_time;
}
}
e->counters.rows += rows;
e->counters.shared_blks_hit += bufusage->shared_blks_hit;
e->counters.shared_blks_read += bufusage->shared_blks_read;
e->counters.shared_blks_dirtied += bufusage->shared_blks_dirtied;
e->counters.shared_blks_written += bufusage->shared_blks_written;
e->counters.local_blks_hit += bufusage->local_blks_hit;
e->counters.local_blks_read += bufusage->local_blks_read;
e->counters.local_blks_dirtied += bufusage->local_blks_dirtied;
e->counters.local_blks_written += bufusage->local_blks_written;
e->counters.temp_blks_read += bufusage->temp_blks_read;
e->counters.temp_blks_written += bufusage->temp_blks_written;
e->counters.shared_blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->shared_blk_read_time);
e->counters.shared_blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->shared_blk_write_time);
e->counters.local_blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->local_blk_read_time);
e->counters.local_blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->local_blk_write_time);
e->counters.temp_blk_read_time += INSTR_TIME_GET_MILLISEC(bufusage->temp_blk_read_time);
e->counters.temp_blk_write_time += INSTR_TIME_GET_MILLISEC(bufusage->temp_blk_write_time);
e->counters.usage += USAGE_EXEC(total_time);
e->counters.wal_records += walusage->wal_records;
e->counters.wal_fpi += walusage->wal_fpi;
e->counters.wal_bytes += walusage->wal_bytes;
if (jitusage)
{
e->counters.jit_functions += jitusage->created_functions;
e->counters.jit_generation_time += INSTR_TIME_GET_MILLISEC(jitusage->generation_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->deform_counter))
e->counters.jit_deform_count++;
e->counters.jit_deform_time += INSTR_TIME_GET_MILLISEC(jitusage->deform_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->inlining_counter))
e->counters.jit_inlining_count++;
e->counters.jit_inlining_time += INSTR_TIME_GET_MILLISEC(jitusage->inlining_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->optimization_counter))
e->counters.jit_optimization_count++;
e->counters.jit_optimization_time += INSTR_TIME_GET_MILLISEC(jitusage->optimization_counter);
if (INSTR_TIME_GET_MILLISEC(jitusage->emission_counter))
e->counters.jit_emission_count++;
e->counters.jit_emission_time += INSTR_TIME_GET_MILLISEC(jitusage->emission_counter);
}
SpinLockRelease(&e->mutex);
}
done:
LWLockRelease(pgss->lock);
/* We postpone this clean-up until we're out of the lock */
if (norm_query)
pfree(norm_query);
}
/*
* Reset statement statistics corresponding to userid, dbid, and queryid.
*/
Datum
pg_stat_statements_reset_1_7(PG_FUNCTION_ARGS)
{
Oid userid;
Oid dbid;
uint64 queryid;
userid = PG_GETARG_OID(0);
dbid = PG_GETARG_OID(1);
queryid = (uint64) PG_GETARG_INT64(2);
entry_reset(userid, dbid, queryid, false);
PG_RETURN_VOID();
}
Datum
pg_stat_statements_reset_1_11(PG_FUNCTION_ARGS)
{
Oid userid;
Oid dbid;
uint64 queryid;
bool minmax_only;
userid = PG_GETARG_OID(0);
dbid = PG_GETARG_OID(1);
queryid = (uint64) PG_GETARG_INT64(2);
minmax_only = PG_GETARG_BOOL(3);
PG_RETURN_TIMESTAMPTZ(entry_reset(userid, dbid, queryid, minmax_only));
}
/*
* Reset statement statistics.
*/
Datum
pg_stat_statements_reset(PG_FUNCTION_ARGS)
{
entry_reset(0, 0, 0, false);
PG_RETURN_VOID();
}
/* Number of output arguments (columns) for various API versions */
#define PG_STAT_STATEMENTS_COLS_V1_0 14
#define PG_STAT_STATEMENTS_COLS_V1_1 18
#define PG_STAT_STATEMENTS_COLS_V1_2 19
#define PG_STAT_STATEMENTS_COLS_V1_3 23
#define PG_STAT_STATEMENTS_COLS_V1_8 32
#define PG_STAT_STATEMENTS_COLS_V1_9 33
#define PG_STAT_STATEMENTS_COLS_V1_10 43
#define PG_STAT_STATEMENTS_COLS_V1_11 49
#define PG_STAT_STATEMENTS_COLS 49 /* maximum of above */
/*
* Retrieve statement statistics.
*
* The SQL API of this function has changed multiple times, and will likely
* do so again in future. To support the case where a newer version of this
* loadable module is being used with an old SQL declaration of the function,
* we continue to support the older API versions. For 1.2 and later, the
* expected API version is identified by embedding it in the C name of the
* function. Unfortunately we weren't bright enough to do that for 1.1.
*/
Datum
pg_stat_statements_1_11(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_11, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_10(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_10, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_9(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_9, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_8(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_8, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_3(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_3, showtext);
return (Datum) 0;
}
Datum
pg_stat_statements_1_2(PG_FUNCTION_ARGS)
{
bool showtext = PG_GETARG_BOOL(0);
pg_stat_statements_internal(fcinfo, PGSS_V1_2, showtext);
return (Datum) 0;
}
/*
* Legacy entry point for pg_stat_statements() API versions 1.0 and 1.1.
* This can be removed someday, perhaps.
*/
Datum
pg_stat_statements(PG_FUNCTION_ARGS)
{
/* If it's really API 1.1, we'll figure that out below */
pg_stat_statements_internal(fcinfo, PGSS_V1_0, true);
return (Datum) 0;
}
/* Common code for all versions of pg_stat_statements() */
static void
pg_stat_statements_internal(FunctionCallInfo fcinfo,
pgssVersion api_version,
bool showtext)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
Oid userid = GetUserId();
bool is_allowed_role = false;
char *qbuffer = NULL;
Size qbuffer_size = 0;
Size extent = 0;
int gc_count = 0;
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
/*
* Superusers or roles with the privileges of pg_read_all_stats members
* are allowed
*/
is_allowed_role = has_privs_of_role(userid, ROLE_PG_READ_ALL_STATS);
/* hash table must exist already */
if (!pgss || !pgss_hash)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
InitMaterializedSRF(fcinfo, 0);
/*
* Check we have the expected number of output arguments. Aside from
* being a good safety check, we need a kluge here to detect API version
* 1.1, which was wedged into the code in an ill-considered way.
*/
switch (rsinfo->setDesc->natts)
{
case PG_STAT_STATEMENTS_COLS_V1_0:
if (api_version != PGSS_V1_0)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_1:
/* pg_stat_statements() should have told us 1.0 */
if (api_version != PGSS_V1_0)
elog(ERROR, "incorrect number of output arguments");
api_version = PGSS_V1_1;
break;
case PG_STAT_STATEMENTS_COLS_V1_2:
if (api_version != PGSS_V1_2)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_3:
if (api_version != PGSS_V1_3)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_8:
if (api_version != PGSS_V1_8)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_9:
if (api_version != PGSS_V1_9)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_10:
if (api_version != PGSS_V1_10)
elog(ERROR, "incorrect number of output arguments");
break;
case PG_STAT_STATEMENTS_COLS_V1_11:
if (api_version != PGSS_V1_11)
elog(ERROR, "incorrect number of output arguments");
break;
default:
elog(ERROR, "incorrect number of output arguments");
}
/*
* We'd like to load the query text file (if needed) while not holding any
* lock on pgss->lock. In the worst case we'll have to do this again
* after we have the lock, but it's unlikely enough to make this a win
* despite occasional duplicated work. We need to reload if anybody
* writes to the file (either a retail qtext_store(), or a garbage
* collection) between this point and where we've gotten shared lock. If
* a qtext_store is actually in progress when we look, we might as well
* skip the speculative load entirely.
*/
if (showtext)
{
int n_writers;
/* Take the mutex so we can examine variables */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
extent = s->extent;
n_writers = s->n_writers;
gc_count = s->gc_count;
SpinLockRelease(&s->mutex);
}
/* No point in loading file now if there are active writers */
if (n_writers == 0)
qbuffer = qtext_load_file(&qbuffer_size);
}
/*
* Get shared lock, load or reload the query text file if we must, and
* iterate over the hashtable entries.
*
* With a large hash table, we might be holding the lock rather longer
* than one could wish. However, this only blocks creation of new hash
* table entries, and the larger the hash table the less likely that is to
* be needed. So we can hope this is okay. Perhaps someday we'll decide
* we need to partition the hash table to limit the time spent holding any
* one lock.
*/
LWLockAcquire(pgss->lock, LW_SHARED);
if (showtext)
{
/*
* Here it is safe to examine extent and gc_count without taking the
* mutex. Note that although other processes might change
* pgss->extent just after we look at it, the strings they then write
* into the file cannot yet be referenced in the hashtable, so we
* don't care whether we see them or not.
*
* If qtext_load_file fails, we just press on; we'll return NULL for
* every query text.
*/
if (qbuffer == NULL ||
pgss->extent != extent ||
pgss->gc_count != gc_count)
{
free(qbuffer);
qbuffer = qtext_load_file(&qbuffer_size);
}
}
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
Datum values[PG_STAT_STATEMENTS_COLS];
bool nulls[PG_STAT_STATEMENTS_COLS];
int i = 0;
Counters tmp;
double stddev;
int64 queryid = entry->key.queryid;
TimestampTz stats_since;
TimestampTz minmax_stats_since;
memset(values, 0, sizeof(values));
memset(nulls, 0, sizeof(nulls));
values[i++] = ObjectIdGetDatum(entry->key.userid);
values[i++] = ObjectIdGetDatum(entry->key.dbid);
if (api_version >= PGSS_V1_9)
values[i++] = BoolGetDatum(entry->key.toplevel);
if (is_allowed_role || entry->key.userid == userid)
{
if (api_version >= PGSS_V1_2)
values[i++] = Int64GetDatumFast(queryid);
if (showtext)
{
char *qstr = qtext_fetch(entry->query_offset,
entry->query_len,
qbuffer,
qbuffer_size);
if (qstr)
{
char *enc;
enc = pg_any_to_server(qstr,
entry->query_len,
entry->encoding);
values[i++] = CStringGetTextDatum(enc);
if (enc != qstr)
pfree(enc);
}
else
{
/* Just return a null if we fail to find the text */
nulls[i++] = true;
}
}
else
{
/* Query text not requested */
nulls[i++] = true;
}
}
else
{
/* Don't show queryid */
if (api_version >= PGSS_V1_2)
nulls[i++] = true;
/*
* Don't show query text, but hint as to the reason for not doing
* so if it was requested
*/
if (showtext)
values[i++] = CStringGetTextDatum("<insufficient privilege>");
else
nulls[i++] = true;
}
/* copy counters to a local variable to keep locking time short */
{
volatile pgssEntry *e = (volatile pgssEntry *) entry;
SpinLockAcquire(&e->mutex);
tmp = e->counters;
stats_since = e->stats_since;
minmax_stats_since = e->minmax_stats_since;
SpinLockRelease(&e->mutex);
}
/* Skip entry if unexecuted (ie, it's a pending "sticky" entry) */
if (IS_STICKY(tmp))
continue;
/* Note that we rely on PGSS_PLAN being 0 and PGSS_EXEC being 1. */
for (int kind = 0; kind < PGSS_NUMKIND; kind++)
{
if (kind == PGSS_EXEC || api_version >= PGSS_V1_8)
{
values[i++] = Int64GetDatumFast(tmp.calls[kind]);
values[i++] = Float8GetDatumFast(tmp.total_time[kind]);
}
if ((kind == PGSS_EXEC && api_version >= PGSS_V1_3) ||
api_version >= PGSS_V1_8)
{
values[i++] = Float8GetDatumFast(tmp.min_time[kind]);
values[i++] = Float8GetDatumFast(tmp.max_time[kind]);
values[i++] = Float8GetDatumFast(tmp.mean_time[kind]);
/*
* Note we are calculating the population variance here, not
* the sample variance, as we have data for the whole
* population, so Bessel's correction is not used, and we
* don't divide by tmp.calls - 1.
*/
if (tmp.calls[kind] > 1)
stddev = sqrt(tmp.sum_var_time[kind] / tmp.calls[kind]);
else
stddev = 0.0;
values[i++] = Float8GetDatumFast(stddev);
}
}
values[i++] = Int64GetDatumFast(tmp.rows);
values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
if (api_version >= PGSS_V1_1)
values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied);
values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
values[i++] = Int64GetDatumFast(tmp.local_blks_read);
if (api_version >= PGSS_V1_1)
values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied);
values[i++] = Int64GetDatumFast(tmp.local_blks_written);
values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
if (api_version >= PGSS_V1_1)
{
values[i++] = Float8GetDatumFast(tmp.shared_blk_read_time);
values[i++] = Float8GetDatumFast(tmp.shared_blk_write_time);
}
if (api_version >= PGSS_V1_11)
{
values[i++] = Float8GetDatumFast(tmp.local_blk_read_time);
values[i++] = Float8GetDatumFast(tmp.local_blk_write_time);
}
if (api_version >= PGSS_V1_10)
{
values[i++] = Float8GetDatumFast(tmp.temp_blk_read_time);
values[i++] = Float8GetDatumFast(tmp.temp_blk_write_time);
}
if (api_version >= PGSS_V1_8)
{
char buf[256];
Datum wal_bytes;
values[i++] = Int64GetDatumFast(tmp.wal_records);
values[i++] = Int64GetDatumFast(tmp.wal_fpi);
snprintf(buf, sizeof buf, UINT64_FORMAT, tmp.wal_bytes);
/* Convert to numeric. */
wal_bytes = DirectFunctionCall3(numeric_in,
CStringGetDatum(buf),
ObjectIdGetDatum(0),
Int32GetDatum(-1));
values[i++] = wal_bytes;
}
if (api_version >= PGSS_V1_10)
{
values[i++] = Int64GetDatumFast(tmp.jit_functions);
values[i++] = Float8GetDatumFast(tmp.jit_generation_time);
values[i++] = Int64GetDatumFast(tmp.jit_inlining_count);
values[i++] = Float8GetDatumFast(tmp.jit_inlining_time);
values[i++] = Int64GetDatumFast(tmp.jit_optimization_count);
values[i++] = Float8GetDatumFast(tmp.jit_optimization_time);
values[i++] = Int64GetDatumFast(tmp.jit_emission_count);
values[i++] = Float8GetDatumFast(tmp.jit_emission_time);
}
if (api_version >= PGSS_V1_11)
{
values[i++] = Int64GetDatumFast(tmp.jit_deform_count);
values[i++] = Float8GetDatumFast(tmp.jit_deform_time);
values[i++] = TimestampTzGetDatum(stats_since);
values[i++] = TimestampTzGetDatum(minmax_stats_since);
}
Assert(i == (api_version == PGSS_V1_0 ? PG_STAT_STATEMENTS_COLS_V1_0 :
api_version == PGSS_V1_1 ? PG_STAT_STATEMENTS_COLS_V1_1 :
api_version == PGSS_V1_2 ? PG_STAT_STATEMENTS_COLS_V1_2 :
api_version == PGSS_V1_3 ? PG_STAT_STATEMENTS_COLS_V1_3 :
api_version == PGSS_V1_8 ? PG_STAT_STATEMENTS_COLS_V1_8 :
api_version == PGSS_V1_9 ? PG_STAT_STATEMENTS_COLS_V1_9 :
api_version == PGSS_V1_10 ? PG_STAT_STATEMENTS_COLS_V1_10 :
api_version == PGSS_V1_11 ? PG_STAT_STATEMENTS_COLS_V1_11 :
-1 /* fail if you forget to update this assert */ ));
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
}
LWLockRelease(pgss->lock);
free(qbuffer);
}
/* Number of output arguments (columns) for pg_stat_statements_info */
#define PG_STAT_STATEMENTS_INFO_COLS 2
/*
* Return statistics of pg_stat_statements.
*/
Datum
pg_stat_statements_info(PG_FUNCTION_ARGS)
{
pgssGlobalStats stats;
TupleDesc tupdesc;
Datum values[PG_STAT_STATEMENTS_INFO_COLS] = {0};
bool nulls[PG_STAT_STATEMENTS_INFO_COLS] = {0};
if (!pgss || !pgss_hash)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
/* Read global statistics for pg_stat_statements */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
stats = s->stats;
SpinLockRelease(&s->mutex);
}
values[0] = Int64GetDatum(stats.dealloc);
values[1] = TimestampTzGetDatum(stats.stats_reset);
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
/*
* Estimate shared memory space needed.
*/
static Size
pgss_memsize(void)
{
Size size;
size = MAXALIGN(sizeof(pgssSharedState));
size = add_size(size, hash_estimate_size(pgss_max, sizeof(pgssEntry)));
return size;
}
/*
* Allocate a new hashtable entry.
* caller must hold an exclusive lock on pgss->lock
*
* "query" need not be null-terminated; we rely on query_len instead
*
* If "sticky" is true, make the new entry artificially sticky so that it will
* probably still be there when the query finishes execution. We do this by
* giving it a median usage value rather than the normal value. (Strictly
* speaking, query strings are normalized on a best effort basis, though it
* would be difficult to demonstrate this even under artificial conditions.)
*
* Note: despite needing exclusive lock, it's not an error for the target
* entry to already exist. This is because pgss_store releases and
* reacquires lock after failing to find a match; so someone else could
* have made the entry while we waited to get exclusive lock.
*/
static pgssEntry *
entry_alloc(pgssHashKey *key, Size query_offset, int query_len, int encoding,
bool sticky)
{
pgssEntry *entry;
bool found;
/* Make space if needed */
while (hash_get_num_entries(pgss_hash) >= pgss_max)
entry_dealloc();
/* Find or create an entry with desired hash code */
entry = (pgssEntry *) hash_search(pgss_hash, key, HASH_ENTER, &found);
if (!found)
{
/* New entry, initialize it */
/* reset the statistics */
memset(&entry->counters, 0, sizeof(Counters));
/* set the appropriate initial usage count */
entry->counters.usage = sticky ? pgss->cur_median_usage : USAGE_INIT;
/* re-initialize the mutex each time ... we assume no one using it */
SpinLockInit(&entry->mutex);
/* ... and don't forget the query text metadata */
Assert(query_len >= 0);
entry->query_offset = query_offset;
entry->query_len = query_len;
entry->encoding = encoding;
entry->stats_since = GetCurrentTimestamp();
entry->minmax_stats_since = entry->stats_since;
}
return entry;
}
/*
* qsort comparator for sorting into increasing usage order
*/
static int
entry_cmp(const void *lhs, const void *rhs)
{
double l_usage = (*(pgssEntry *const *) lhs)->counters.usage;
double r_usage = (*(pgssEntry *const *) rhs)->counters.usage;
if (l_usage < r_usage)
return -1;
else if (l_usage > r_usage)
return +1;
else
return 0;
}
/*
* Deallocate least-used entries.
*
* Caller must hold an exclusive lock on pgss->lock.
*/
static void
entry_dealloc(void)
{
HASH_SEQ_STATUS hash_seq;
pgssEntry **entries;
pgssEntry *entry;
int nvictims;
int i;
Size tottextlen;
int nvalidtexts;
/*
* Sort entries by usage and deallocate USAGE_DEALLOC_PERCENT of them.
* While we're scanning the table, apply the decay factor to the usage
* values, and update the mean query length.
*
* Note that the mean query length is almost immediately obsolete, since
* we compute it before not after discarding the least-used entries.
* Hopefully, that doesn't affect the mean too much; it doesn't seem worth
* making two passes to get a more current result. Likewise, the new
* cur_median_usage includes the entries we're about to zap.
*/
entries = palloc(hash_get_num_entries(pgss_hash) * sizeof(pgssEntry *));
i = 0;
tottextlen = 0;
nvalidtexts = 0;
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
entries[i++] = entry;
/* "Sticky" entries get a different usage decay rate. */
if (IS_STICKY(entry->counters))
entry->counters.usage *= STICKY_DECREASE_FACTOR;
else
entry->counters.usage *= USAGE_DECREASE_FACTOR;
/* In the mean length computation, ignore dropped texts. */
if (entry->query_len >= 0)
{
tottextlen += entry->query_len + 1;
nvalidtexts++;
}
}
/* Sort into increasing order by usage */
qsort(entries, i, sizeof(pgssEntry *), entry_cmp);
/* Record the (approximate) median usage */
if (i > 0)
pgss->cur_median_usage = entries[i / 2]->counters.usage;
/* Record the mean query length */
if (nvalidtexts > 0)
pgss->mean_query_len = tottextlen / nvalidtexts;
else
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
/* Now zap an appropriate fraction of lowest-usage entries */
nvictims = Max(10, i * USAGE_DEALLOC_PERCENT / 100);
nvictims = Min(nvictims, i);
for (i = 0; i < nvictims; i++)
{
hash_search(pgss_hash, &entries[i]->key, HASH_REMOVE, NULL);
}
pfree(entries);
/* Increment the number of times entries are deallocated */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->stats.dealloc += 1;
SpinLockRelease(&s->mutex);
}
}
/*
* Given a query string (not necessarily null-terminated), allocate a new
* entry in the external query text file and store the string there.
*
* If successful, returns true, and stores the new entry's offset in the file
* into *query_offset. Also, if gc_count isn't NULL, *gc_count is set to the
* number of garbage collections that have occurred so far.
*
* On failure, returns false.
*
* At least a shared lock on pgss->lock must be held by the caller, so as
* to prevent a concurrent garbage collection. Share-lock-holding callers
* should pass a gc_count pointer to obtain the number of garbage collections,
* so that they can recheck the count after obtaining exclusive lock to
* detect whether a garbage collection occurred (and removed this entry).
*/
static bool
qtext_store(const char *query, int query_len,
Size *query_offset, int *gc_count)
{
Size off;
int fd;
/*
* We use a spinlock to protect extent/n_writers/gc_count, so that
* multiple processes may execute this function concurrently.
*/
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
off = s->extent;
s->extent += query_len + 1;
s->n_writers++;
if (gc_count)
*gc_count = s->gc_count;
SpinLockRelease(&s->mutex);
}
*query_offset = off;
/*
* Don't allow the file to grow larger than what qtext_load_file can
* (theoretically) handle. This has been seen to be reachable on 32-bit
* platforms.
*/
if (unlikely(query_len >= MaxAllocHugeSize - off))
{
errno = EFBIG; /* not quite right, but it'll do */
fd = -1;
goto error;
}
/* Now write the data into the successfully-reserved part of the file */
fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDWR | O_CREAT | PG_BINARY);
if (fd < 0)
goto error;
if (pg_pwrite(fd, query, query_len, off) != query_len)
goto error;
if (pg_pwrite(fd, "\0", 1, off + query_len) != 1)
goto error;
CloseTransientFile(fd);
/* Mark our write complete */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->n_writers--;
SpinLockRelease(&s->mutex);
}
return true;
error:
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
if (fd >= 0)
CloseTransientFile(fd);
/* Mark our write complete */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->n_writers--;
SpinLockRelease(&s->mutex);
}
return false;
}
/*
* Read the external query text file into a malloc'd buffer.
*
* Returns NULL (without throwing an error) if unable to read, eg
* file not there or insufficient memory.
*
* On success, the buffer size is also returned into *buffer_size.
*
* This can be called without any lock on pgss->lock, but in that case
* the caller is responsible for verifying that the result is sane.
*/
static char *
qtext_load_file(Size *buffer_size)
{
char *buf;
int fd;
struct stat stat;
Size nread;
fd = OpenTransientFile(PGSS_TEXT_FILE, O_RDONLY | PG_BINARY);
if (fd < 0)
{
if (errno != ENOENT)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
PGSS_TEXT_FILE)));
return NULL;
}
/* Get file length */
if (fstat(fd, &stat))
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not stat file \"%s\": %m",
PGSS_TEXT_FILE)));
CloseTransientFile(fd);
return NULL;
}
/* Allocate buffer; beware that off_t might be wider than size_t */
if (stat.st_size <= MaxAllocHugeSize)
buf = (char *) malloc(stat.st_size);
else
buf = NULL;
if (buf == NULL)
{
ereport(LOG,
(errcode(ERRCODE_OUT_OF_MEMORY),
errmsg("out of memory"),
errdetail("Could not allocate enough memory to read file \"%s\".",
PGSS_TEXT_FILE)));
CloseTransientFile(fd);
return NULL;
}
/*
* OK, slurp in the file. Windows fails if we try to read more than
* INT_MAX bytes at once, and other platforms might not like that either,
* so read a very large file in 1GB segments.
*/
nread = 0;
while (nread < stat.st_size)
{
int toread = Min(1024 * 1024 * 1024, stat.st_size - nread);
/*
* If we get a short read and errno doesn't get set, the reason is
* probably that garbage collection truncated the file since we did
* the fstat(), so we don't log a complaint --- but we don't return
* the data, either, since it's most likely corrupt due to concurrent
* writes from garbage collection.
*/
errno = 0;
if (read(fd, buf + nread, toread) != toread)
{
if (errno)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not read file \"%s\": %m",
PGSS_TEXT_FILE)));
free(buf);
CloseTransientFile(fd);
return NULL;
}
nread += toread;
}
if (CloseTransientFile(fd) != 0)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not close file \"%s\": %m", PGSS_TEXT_FILE)));
*buffer_size = nread;
return buf;
}
/*
* Locate a query text in the file image previously read by qtext_load_file().
*
* We validate the given offset/length, and return NULL if bogus. Otherwise,
* the result points to a null-terminated string within the buffer.
*/
static char *
qtext_fetch(Size query_offset, int query_len,
char *buffer, Size buffer_size)
{
/* File read failed? */
if (buffer == NULL)
return NULL;
/* Bogus offset/length? */
if (query_len < 0 ||
query_offset + query_len >= buffer_size)
return NULL;
/* As a further sanity check, make sure there's a trailing null */
if (buffer[query_offset + query_len] != '\0')
return NULL;
/* Looks OK */
return buffer + query_offset;
}
/*
* Do we need to garbage-collect the external query text file?
*
* Caller should hold at least a shared lock on pgss->lock.
*/
static bool
need_gc_qtexts(void)
{
Size extent;
/* Read shared extent pointer */
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
extent = s->extent;
SpinLockRelease(&s->mutex);
}
/*
* Don't proceed if file does not exceed 512 bytes per possible entry.
*
* Here and in the next test, 32-bit machines have overflow hazards if
* pgss_max and/or mean_query_len are large. Force the multiplications
* and comparisons to be done in uint64 arithmetic to forestall trouble.
*/
if ((uint64) extent < (uint64) 512 * pgss_max)
return false;
/*
* Don't proceed if file is less than about 50% bloat. Nothing can or
* should be done in the event of unusually large query texts accounting
* for file's large size. We go to the trouble of maintaining the mean
* query length in order to prevent garbage collection from thrashing
* uselessly.
*/
if ((uint64) extent < (uint64) pgss->mean_query_len * pgss_max * 2)
return false;
return true;
}
/*
* Garbage-collect orphaned query texts in external file.
*
* This won't be called often in the typical case, since it's likely that
* there won't be too much churn, and besides, a similar compaction process
* occurs when serializing to disk at shutdown or as part of resetting.
* Despite this, it seems prudent to plan for the edge case where the file
* becomes unreasonably large, with no other method of compaction likely to
* occur in the foreseeable future.
*
* The caller must hold an exclusive lock on pgss->lock.
*
* At the first sign of trouble we unlink the query text file to get a clean
* slate (although existing statistics are retained), rather than risk
* thrashing by allowing the same problem case to recur indefinitely.
*/
static void
gc_qtexts(void)
{
char *qbuffer;
Size qbuffer_size;
FILE *qfile = NULL;
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
Size extent;
int nentries;
/*
* When called from pgss_store, some other session might have proceeded
* with garbage collection in the no-lock-held interim of lock strength
* escalation. Check once more that this is actually necessary.
*/
if (!need_gc_qtexts())
return;
/*
* Load the old texts file. If we fail (out of memory, for instance),
* invalidate query texts. Hopefully this is rare. It might seem better
* to leave things alone on an OOM failure, but the problem is that the
* file is only going to get bigger; hoping for a future non-OOM result is
* risky and can easily lead to complete denial of service.
*/
qbuffer = qtext_load_file(&qbuffer_size);
if (qbuffer == NULL)
goto gc_fail;
/*
* We overwrite the query texts file in place, so as to reduce the risk of
* an out-of-disk-space failure. Since the file is guaranteed not to get
* larger, this should always work on traditional filesystems; though we
* could still lose on copy-on-write filesystems.
*/
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
goto gc_fail;
}
extent = 0;
nentries = 0;
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
int query_len = entry->query_len;
char *qry = qtext_fetch(entry->query_offset,
query_len,
qbuffer,
qbuffer_size);
if (qry == NULL)
{
/* Trouble ... drop the text */
entry->query_offset = 0;
entry->query_len = -1;
/* entry will not be counted in mean query length computation */
continue;
}
if (fwrite(qry, 1, query_len + 1, qfile) != query_len + 1)
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
hash_seq_term(&hash_seq);
goto gc_fail;
}
entry->query_offset = extent;
extent += query_len + 1;
nentries++;
}
/*
* Truncate away any now-unused space. If this fails for some odd reason,
* we log it, but there's no need to fail.
*/
if (ftruncate(fileno(qfile), extent) != 0)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\": %m",
PGSS_TEXT_FILE)));
if (FreeFile(qfile))
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not write file \"%s\": %m",
PGSS_TEXT_FILE)));
qfile = NULL;
goto gc_fail;
}
elog(DEBUG1, "pgss gc of queries file shrunk size from %zu to %zu",
pgss->extent, extent);
/* Reset the shared extent pointer */
pgss->extent = extent;
/*
* Also update the mean query length, to be sure that need_gc_qtexts()
* won't still think we have a problem.
*/
if (nentries > 0)
pgss->mean_query_len = extent / nentries;
else
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
free(qbuffer);
/*
* OK, count a garbage collection cycle. (Note: even though we have
* exclusive lock on pgss->lock, we must take pgss->mutex for this, since
* other processes may examine gc_count while holding only the mutex.
* Also, we have to advance the count *after* we've rewritten the file,
* else other processes might not realize they read a stale file.)
*/
record_gc_qtexts();
return;
gc_fail:
/* clean up resources */
if (qfile)
FreeFile(qfile);
free(qbuffer);
/*
* Since the contents of the external file are now uncertain, mark all
* hashtable entries as having invalid texts.
*/
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
entry->query_offset = 0;
entry->query_len = -1;
}
/*
* Destroy the query text file and create a new, empty one
*/
(void) unlink(PGSS_TEXT_FILE);
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not recreate file \"%s\": %m",
PGSS_TEXT_FILE)));
else
FreeFile(qfile);
/* Reset the shared extent pointer */
pgss->extent = 0;
/* Reset mean_query_len to match the new state */
pgss->mean_query_len = ASSUMED_LENGTH_INIT;
/*
* Bump the GC count even though we failed.
*
* This is needed to make concurrent readers of file without any lock on
* pgss->lock notice existence of new version of file. Once readers
* subsequently observe a change in GC count with pgss->lock held, that
* forces a safe reopen of file. Writers also require that we bump here,
* of course. (As required by locking protocol, readers and writers don't
* trust earlier file contents until gc_count is found unchanged after
* pgss->lock acquired in shared or exclusive mode respectively.)
*/
record_gc_qtexts();
}
#define SINGLE_ENTRY_RESET(e) \
if (e) { \
if (minmax_only) { \
/* When requested reset only min/max statistics of an entry */ \
for (int kind = 0; kind < PGSS_NUMKIND; kind++) \
{ \
e->counters.max_time[kind] = 0; \
e->counters.min_time[kind] = 0; \
} \
e->minmax_stats_since = stats_reset; \
} \
else \
{ \
/* Remove the key otherwise */ \
hash_search(pgss_hash, &e->key, HASH_REMOVE, NULL); \
num_remove++; \
} \
}
/*
* Reset entries corresponding to parameters passed.
*/
static TimestampTz
entry_reset(Oid userid, Oid dbid, uint64 queryid, bool minmax_only)
{
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
FILE *qfile;
long num_entries;
long num_remove = 0;
pgssHashKey key;
TimestampTz stats_reset;
if (!pgss || !pgss_hash)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("pg_stat_statements must be loaded via shared_preload_libraries")));
LWLockAcquire(pgss->lock, LW_EXCLUSIVE);
num_entries = hash_get_num_entries(pgss_hash);
stats_reset = GetCurrentTimestamp();
if (userid != 0 && dbid != 0 && queryid != UINT64CONST(0))
{
/* If all the parameters are available, use the fast path. */
memset(&key, 0, sizeof(pgssHashKey));
key.userid = userid;
key.dbid = dbid;
key.queryid = queryid;
/*
* Reset the entry if it exists, starting with the non-top-level
* entry.
*/
key.toplevel = false;
entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_FIND, NULL);
SINGLE_ENTRY_RESET(entry);
/* Also reset the top-level entry if it exists. */
key.toplevel = true;
entry = (pgssEntry *) hash_search(pgss_hash, &key, HASH_FIND, NULL);
SINGLE_ENTRY_RESET(entry);
}
else if (userid != 0 || dbid != 0 || queryid != UINT64CONST(0))
{
/* Reset entries corresponding to valid parameters. */
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
if ((!userid || entry->key.userid == userid) &&
(!dbid || entry->key.dbid == dbid) &&
(!queryid || entry->key.queryid == queryid))
{
SINGLE_ENTRY_RESET(entry);
}
}
}
else
{
/* Reset all entries. */
hash_seq_init(&hash_seq, pgss_hash);
while ((entry = hash_seq_search(&hash_seq)) != NULL)
{
SINGLE_ENTRY_RESET(entry);
}
}
/* All entries are removed? */
if (num_entries != num_remove)
goto release_lock;
/*
* Reset global statistics for pg_stat_statements since all entries are
* removed.
*/
{
volatile pgssSharedState *s = (volatile pgssSharedState *) pgss;
SpinLockAcquire(&s->mutex);
s->stats.dealloc = 0;
s->stats.stats_reset = stats_reset;
SpinLockRelease(&s->mutex);
}
/*
* Write new empty query file, perhaps even creating a new one to recover
* if the file was missing.
*/
qfile = AllocateFile(PGSS_TEXT_FILE, PG_BINARY_W);
if (qfile == NULL)
{
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not create file \"%s\": %m",
PGSS_TEXT_FILE)));
goto done;
}
/* If ftruncate fails, log it, but it's not a fatal problem */
if (ftruncate(fileno(qfile), 0) != 0)
ereport(LOG,
(errcode_for_file_access(),
errmsg("could not truncate file \"%s\": %m",
PGSS_TEXT_FILE)));
FreeFile(qfile);
done:
pgss->extent = 0;
/* This counts as a query text garbage collection for our purposes */
record_gc_qtexts();
release_lock:
LWLockRelease(pgss->lock);
return stats_reset;
}
/*
* Generate a normalized version of the query string that will be used to
* represent all similar queries.
*
* Note that the normalized representation may well vary depending on
* just which "equivalent" query is used to create the hashtable entry.
* We assume this is OK.
*
* If query_loc > 0, then "query" has been advanced by that much compared to
* the original string start, so we need to translate the provided locations
* to compensate. (This lets us avoid re-scanning statements before the one
* of interest, so it's worth doing.)
*
* *query_len_p contains the input string length, and is updated with
* the result string length on exit. The resulting string might be longer
* or shorter depending on what happens with replacement of constants.
*
* Returns a palloc'd string.
*/
static char *
generate_normalized_query(JumbleState *jstate, const char *query,
int query_loc, int *query_len_p)
{
char *norm_query;
int query_len = *query_len_p;
int i,
norm_query_buflen, /* Space allowed for norm_query */
len_to_wrt, /* Length (in bytes) to write */
quer_loc = 0, /* Source query byte location */
n_quer_loc = 0, /* Normalized query byte location */
last_off = 0, /* Offset from start for previous tok */
last_tok_len = 0; /* Length (in bytes) of that tok */
/*
* Get constants' lengths (core system only gives us locations). Note
* this also ensures the items are sorted by location.
*/
fill_in_constant_lengths(jstate, query, query_loc);
/*
* Allow for $n symbols to be longer than the constants they replace.
* Constants must take at least one byte in text form, while a $n symbol
* certainly isn't more than 11 bytes, even if n reaches INT_MAX. We
* could refine that limit based on the max value of n for the current
* query, but it hardly seems worth any extra effort to do so.
*/
norm_query_buflen = query_len + jstate->clocations_count * 10;
/* Allocate result buffer */
norm_query = palloc(norm_query_buflen + 1);
for (i = 0; i < jstate->clocations_count; i++)
{
int off, /* Offset from start for cur tok */
tok_len; /* Length (in bytes) of that tok */
off = jstate->clocations[i].location;
/* Adjust recorded location if we're dealing with partial string */
off -= query_loc;
tok_len = jstate->clocations[i].length;
if (tok_len < 0)
continue; /* ignore any duplicates */
/* Copy next chunk (what precedes the next constant) */
len_to_wrt = off - last_off;
len_to_wrt -= last_tok_len;
Assert(len_to_wrt >= 0);
memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
n_quer_loc += len_to_wrt;
/* And insert a param symbol in place of the constant token */
n_quer_loc += sprintf(norm_query + n_quer_loc, "$%d",
i + 1 + jstate->highest_extern_param_id);
quer_loc = off + tok_len;
last_off = off;
last_tok_len = tok_len;
}
/*
* We've copied up until the last ignorable constant. Copy over the
* remaining bytes of the original query string.
*/
len_to_wrt = query_len - quer_loc;
Assert(len_to_wrt >= 0);
memcpy(norm_query + n_quer_loc, query + quer_loc, len_to_wrt);
n_quer_loc += len_to_wrt;
Assert(n_quer_loc <= norm_query_buflen);
norm_query[n_quer_loc] = '\0';
*query_len_p = n_quer_loc;
return norm_query;
}
/*
* Given a valid SQL string and an array of constant-location records,
* fill in the textual lengths of those constants.
*
* The constants may use any allowed constant syntax, such as float literals,
* bit-strings, single-quoted strings and dollar-quoted strings. This is
* accomplished by using the public API for the core scanner.
*
* It is the caller's job to ensure that the string is a valid SQL statement
* with constants at the indicated locations. Since in practice the string
* has already been parsed, and the locations that the caller provides will
* have originated from within the authoritative parser, this should not be
* a problem.
*
* Duplicate constant pointers are possible, and will have their lengths
* marked as '-1', so that they are later ignored. (Actually, we assume the
* lengths were initialized as -1 to start with, and don't change them here.)
*
* If query_loc > 0, then "query" has been advanced by that much compared to
* the original string start, so we need to translate the provided locations
* to compensate. (This lets us avoid re-scanning statements before the one
* of interest, so it's worth doing.)
*
* N.B. There is an assumption that a '-' character at a Const location begins
* a negative numeric constant. This precludes there ever being another
* reason for a constant to start with a '-'.
*/
static void
fill_in_constant_lengths(JumbleState *jstate, const char *query,
int query_loc)
{
LocationLen *locs;
core_yyscan_t yyscanner;
core_yy_extra_type yyextra;
core_YYSTYPE yylval;
YYLTYPE yylloc;
int last_loc = -1;
int i;
/*
* Sort the records by location so that we can process them in order while
* scanning the query text.
*/
if (jstate->clocations_count > 1)
qsort(jstate->clocations, jstate->clocations_count,
sizeof(LocationLen), comp_location);
locs = jstate->clocations;
/* initialize the flex scanner --- should match raw_parser() */
yyscanner = scanner_init(query,
&yyextra,
&ScanKeywords,
ScanKeywordTokens);
/* we don't want to re-emit any escape string warnings */
yyextra.escape_string_warning = false;
/* Search for each constant, in sequence */
for (i = 0; i < jstate->clocations_count; i++)
{
int loc = locs[i].location;
int tok;
/* Adjust recorded location if we're dealing with partial string */
loc -= query_loc;
Assert(loc >= 0);
if (loc <= last_loc)
continue; /* Duplicate constant, ignore */
/* Lex tokens until we find the desired constant */
for (;;)
{
tok = core_yylex(&yylval, &yylloc, yyscanner);
/* We should not hit end-of-string, but if we do, behave sanely */
if (tok == 0)
break; /* out of inner for-loop */
/*
* We should find the token position exactly, but if we somehow
* run past it, work with that.
*/
if (yylloc >= loc)
{
if (query[loc] == '-')
{
/*
* It's a negative value - this is the one and only case
* where we replace more than a single token.
*
* Do not compensate for the core system's special-case
* adjustment of location to that of the leading '-'
* operator in the event of a negative constant. It is
* also useful for our purposes to start from the minus
* symbol. In this way, queries like "select * from foo
* where bar = 1" and "select * from foo where bar = -2"
* will have identical normalized query strings.
*/
tok = core_yylex(&yylval, &yylloc, yyscanner);
if (tok == 0)
break; /* out of inner for-loop */
}
/*
* We now rely on the assumption that flex has placed a zero
* byte after the text of the current token in scanbuf.
*/
locs[i].length = strlen(yyextra.scanbuf + loc);
break; /* out of inner for-loop */
}
}
/* If we hit end-of-string, give up, leaving remaining lengths -1 */
if (tok == 0)
break;
last_loc = loc;
}
scanner_finish(yyscanner);
}
/*
* comp_location: comparator for qsorting LocationLen structs by location
*/
static int
comp_location(const void *a, const void *b)
{
int l = ((const LocationLen *) a)->location;
int r = ((const LocationLen *) b)->location;
return pg_cmp_s32(l, r);
}
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