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Expose qurey ID in pg_stat_statements view.

Browse Source 
The query ID is the internal hash identifier of the statement,
and was not available in pg_stat_statements view so far.

Daniel Farina, Sameer Thakur and Peter Geoghegan, reviewed by me.
pull/6/head
Fujii Masao 12 years ago
parent ef3267523d
commit 91484409bd
7 changed files with 202 additions and 71 deletions
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
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  1. 4
      contrib/pg_stat_statements/Makefile
  2. 43
      contrib/pg_stat_statements/pg_stat_statements--1.1--1.2.sql
  3. 43
      contrib/pg_stat_statements/pg_stat_statements--1.1.sql
  4. 44
      contrib/pg_stat_statements/pg_stat_statements--1.2.sql
  5. 62
      contrib/pg_stat_statements/pg_stat_statements.c
  6. 2
      contrib/pg_stat_statements/pg_stat_statements.control
  7. 75
      doc/src/sgml/pgstatstatements.sgml

4
contrib/pg_stat_statements/Makefile
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@ -4,8 +4,8 @@ MODULE_big = pg_stat_statements
OBJS = pg_stat_statements.o
EXTENSION = pg_stat_statements
DATA = pg_stat_statements--1.1.sql pg_stat_statements--1.0--1.1.sql \
pg_stat_statements--unpackaged--1.0.sql
DATA = pg_stat_statements--1.2.sql pg_stat_statements--1.1--1.2.sql \
pg_stat_statements--1.0--1.1.sql pg_stat_statements--unpackaged--1.0.sql
ifdef USE_PGXS
PG_CONFIG = pg_config

43
contrib/pg_stat_statements/pg_stat_statements--1.1--1.2.sql
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@ -0,0 +1,43 @@
/* contrib/pg_stat_statements/pg_stat_statements--1.1--1.2.sql */
-- complain if script is sourced in psql, rather than via ALTER EXTENSION
\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.2'" to load this file. \quit
/* First we have to remove them from the extension */
ALTER EXTENSION pg_stat_statements DROP VIEW pg_stat_statements;
ALTER EXTENSION pg_stat_statements DROP FUNCTION pg_stat_statements();
/* Then we can drop them */
DROP VIEW pg_stat_statements;
DROP FUNCTION pg_stat_statements();
/* Now redefine */
CREATE FUNCTION pg_stat_statements(
OUT userid oid,
OUT dbid oid,
OUT queryid bigint,
OUT query text,
OUT calls int8,
OUT total_time float8,
OUT rows int8,
OUT shared_blks_hit int8,
OUT shared_blks_read int8,
OUT shared_blks_dirtied int8,
OUT shared_blks_written int8,
OUT local_blks_hit int8,
OUT local_blks_read int8,
OUT local_blks_dirtied int8,
OUT local_blks_written int8,
OUT temp_blks_read int8,
OUT temp_blks_written int8,
OUT blk_read_time float8,
OUT blk_write_time float8
)
RETURNS SETOF record
AS 'MODULE_PATHNAME'
LANGUAGE C;
CREATE VIEW pg_stat_statements AS
SELECT * FROM pg_stat_statements();
GRANT SELECT ON pg_stat_statements TO PUBLIC;

43
contrib/pg_stat_statements/pg_stat_statements--1.1.sql
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@ -1,43 +0,0 @@
/* contrib/pg_stat_statements/pg_stat_statements--1.1.sql */
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
-- Register functions.
CREATE FUNCTION pg_stat_statements_reset()
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C;
CREATE FUNCTION pg_stat_statements(
OUT userid oid,
OUT dbid oid,
OUT query text,
OUT calls int8,
OUT total_time float8,
OUT rows int8,
OUT shared_blks_hit int8,
OUT shared_blks_read int8,
OUT shared_blks_dirtied int8,
OUT shared_blks_written int8,
OUT local_blks_hit int8,
OUT local_blks_read int8,
OUT local_blks_dirtied int8,
OUT local_blks_written int8,
OUT temp_blks_read int8,
OUT temp_blks_written int8,
OUT blk_read_time float8,
OUT blk_write_time float8
)
RETURNS SETOF record
AS 'MODULE_PATHNAME'
LANGUAGE C;
-- Register a view on the function for ease of use.
CREATE VIEW pg_stat_statements AS
SELECT * FROM pg_stat_statements();
GRANT SELECT ON pg_stat_statements TO PUBLIC;
-- Don't want this to be available to non-superusers.
REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;

44
contrib/pg_stat_statements/pg_stat_statements--1.2.sql
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@ -0,0 +1,44 @@
/* contrib/pg_stat_statements/pg_stat_statements--1.2.sql */
-- complain if script is sourced in psql, rather than via CREATE EXTENSION
\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
-- Register functions.
CREATE FUNCTION pg_stat_statements_reset()
RETURNS void
AS 'MODULE_PATHNAME'
LANGUAGE C;
CREATE FUNCTION pg_stat_statements(
OUT userid oid,
OUT dbid oid,
OUT queryid bigint,
OUT query text,
OUT calls int8,
OUT total_time float8,
OUT rows int8,
OUT shared_blks_hit int8,
OUT shared_blks_read int8,
OUT shared_blks_dirtied int8,
OUT shared_blks_written int8,
OUT local_blks_hit int8,
OUT local_blks_read int8,
OUT local_blks_dirtied int8,
OUT local_blks_written int8,
OUT temp_blks_read int8,
OUT temp_blks_written int8,
OUT blk_read_time float8,
OUT blk_write_time float8
)
RETURNS SETOF record
AS 'MODULE_PATHNAME'
LANGUAGE C;
-- Register a view on the function for ease of use.
CREATE VIEW pg_stat_statements AS
SELECT * FROM pg_stat_statements();
GRANT SELECT ON pg_stat_statements TO PUBLIC;
-- Don't want this to be available to non-superusers.
REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;

62
contrib/pg_stat_statements/pg_stat_statements.c
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@ -67,7 +67,9 @@ PG_MODULE_MAGIC;
#define PGSS_DUMP_FILE "global/pg_stat_statements.stat"
/* This constant defines the magic number in the stats file header */
static const uint32 PGSS_FILE_HEADER = 0x20120328;
static const uint32 PGSS_FILE_HEADER = 0x20131115;
/* 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)
@ -79,6 +81,16 @@ static const uint32 PGSS_FILE_HEADER = 0x20120328;
#define JUMBLE_SIZE 1024 /* query serialization buffer size */
/*
* Extension version number, for supporting older extension versions' objects
*/
typedef enum pgssVersion
{
PGSS_V1_0 = 0,
PGSS_V1_1,
PGSS_V1_2
} pgssVersion;
/*
* Hashtable key that defines the identity of a hashtable entry. We separate
* queries by user and by database even if they are otherwise identical.
@ -390,6 +402,7 @@ pgss_shmem_startup(void)
FILE *file;
uint32 header;
int32 num;
int32 pgver;
int32 i;
int query_size;
int buffer_size;
@ -465,6 +478,8 @@ pgss_shmem_startup(void)
if (fread(&header, sizeof(uint32), 1, file) != 1 ||
header != PGSS_FILE_HEADER ||
fread(&pgver, sizeof(uint32), 1, file) != 1 ||
pgver != PGSS_PG_MAJOR_VERSION ||
fread(&num, sizeof(int32), 1, file) != 1)
goto error;
@ -565,6 +580,8 @@ pgss_shmem_shutdown(int code, Datum arg)
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;
@ -1069,7 +1086,8 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
}
#define PG_STAT_STATEMENTS_COLS_V1_0 14
#define PG_STAT_STATEMENTS_COLS 18
#define PG_STAT_STATEMENTS_COLS_V1_1 18
#define PG_STAT_STATEMENTS_COLS 19
/*
* Retrieve statement statistics.
@ -1086,7 +1104,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
bool is_superuser = superuser();
HASH_SEQ_STATUS hash_seq;
pgssEntry *entry;
bool sql_supports_v1_1_counters = true;
pgssVersion detected_version;
if (!pgss || !pgss_hash)
ereport(ERROR,
@ -1107,8 +1125,21 @@ pg_stat_statements(PG_FUNCTION_ARGS)
/* 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");
if (tupdesc->natts == PG_STAT_STATEMENTS_COLS_V1_0)
sql_supports_v1_1_counters = false;
switch (tupdesc->natts)
{
case PG_STAT_STATEMENTS_COLS_V1_0:
detected_version = PGSS_V1_0;
break;
case PG_STAT_STATEMENTS_COLS_V1_1:
detected_version = PGSS_V1_1;
break;
case PG_STAT_STATEMENTS_COLS:
detected_version = PGSS_V1_2;
break;
default:
elog(ERROR, "pgss version unrecognized from tuple descriptor");
}
per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
oldcontext = MemoryContextSwitchTo(per_query_ctx);
@ -1140,6 +1171,9 @@ pg_stat_statements(PG_FUNCTION_ARGS)
{
char *qstr;
if (detected_version >= PGSS_V1_2)
values[i++] = Int64GetDatumFast((int64) entry->key.queryid);
qstr = (char *)
pg_do_encoding_conversion((unsigned char *) entry->query,
entry->query_len,
@ -1150,7 +1184,12 @@ pg_stat_statements(PG_FUNCTION_ARGS)
pfree(qstr);
}
else
{
if (detected_version >= PGSS_V1_2)
nulls[i++] = true;
values[i++] = CStringGetTextDatum("<insufficient privilege>");
}
/* copy counters to a local variable to keep locking time short */
{
@ -1170,24 +1209,27 @@ pg_stat_statements(PG_FUNCTION_ARGS)
values[i++] = Int64GetDatumFast(tmp.rows);
values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
if (sql_supports_v1_1_counters)
if (detected_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 (sql_supports_v1_1_counters)
if (detected_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 (sql_supports_v1_1_counters)
if (detected_version >= PGSS_V1_1)
{
values[i++] = Float8GetDatumFast(tmp.blk_read_time);
values[i++] = Float8GetDatumFast(tmp.blk_write_time);
}
Assert(i == (sql_supports_v1_1_counters ?
PG_STAT_STATEMENTS_COLS : PG_STAT_STATEMENTS_COLS_V1_0));
Assert(i == (detected_version == PGSS_V1_0?
PG_STAT_STATEMENTS_COLS_V1_0:
detected_version == PGSS_V1_1?
PG_STAT_STATEMENTS_COLS_V1_1:
PG_STAT_STATEMENTS_COLS));
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
}

2
contrib/pg_stat_statements/pg_stat_statements.control
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@ -1,5 +1,5 @@
# pg_stat_statements extension
comment = 'track execution statistics of all SQL statements executed'
default_version = '1.1'
default_version = '1.2'
module_pathname = '$libdir/pg_stat_statements'
relocatable = true

75
doc/src/sgml/pgstatstatements.sgml
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@ -23,11 +23,12 @@
<title>The <structname>pg_stat_statements</structname> View</title>
<para>
The statistics gathered by the module are made available via a system view
named <structname>pg_stat_statements</>. This view contains one row for
each distinct query, database ID, and user ID (up to the maximum
number of distinct statements that the module can track). The columns
of the view are shown in <xref linkend="pgstatstatements-columns">.
The statistics gathered by the module are made available via a
system view named <structname>pg_stat_statements</>. This view
contains one row for each distinct database ID, user ID and query
ID (up to the maximum number of distinct statements that the module
can track). The columns of the view are shown in
<xref linkend="pgstatstatements-columns">.
</para>
<table id="pgstatstatements-columns">
@ -57,7 +58,14 @@
<entry>OID of database in which the statement was executed</entry>
</row>
<row>
<row>
<entry><structfield>queryid</structfield></entry>
<entry><type>bigint</type></entry>
<entry></entry>
<entry>Internal hash identifier, computed from the entry's post-parse-analysis tree</entry>
</row>
<row>
<entry><structfield>query</structfield></entry>
<entry><type>text</type></entry>
<entry></entry>
@ -189,9 +197,10 @@
</para>
<para>
For security reasons, non-superusers are not allowed to see the text of
queries executed by other users. They can see the statistics, however,
if the view has been installed in their database.
For security reasons, non-superusers are not allowed to see the SQL
text or queryid of queries executed by other users. They can see
the statistics, however, if the view has been installed in their
database.
</para>
<para>
@ -209,8 +218,9 @@
When a constant's value has been ignored for purposes of matching the
query to other queries, the constant is replaced by <literal>?</literal>
in the <structname>pg_stat_statements</> display. The rest of the query
text is that of the first query that had the particular hash value
associated with the <structname>pg_stat_statements</> entry.
text is that of the first query that had the particular
<structfield>queryid</> hash value associated with the
<structname>pg_stat_statements</> entry.
</para>
<para>
@ -223,10 +233,45 @@
</para>
<para>
Since the hash value is computed on the post-parse-analysis representation
of the queries, the opposite is also possible: queries with identical texts
might appear as separate entries, if they have different meanings as a
result of factors such as different <varname>search_path</> settings.
Since the <structfield>queryid</> hash value is computed on the
post-parse-analysis representation of the queries, the opposite is
also possible: queries with identical texts might appear as
separate entries, if they have different meanings as a result of
factors such as different <varname>search_path</> settings.
</para>
<para>
Consumers of <literal>pg_stat_statements</> may wish to use
<structfield>queryid</> (perhaps in composite with
<structfield>dbid</> and <structfield>userid</>) as a more stable
and reliable identifier for each entry than its query text.
However, it is important to understand that there are only limited
guarantees around the stability of the <structfield>queryid</> hash
value. Since the identifier is derived from the
post-parse-analysis tree, its value is a function of, among other
things, the internal identifiers that comprise this representation.
This has some counterintuitive implications. For example, a query
against a table that is fingerprinted by
<literal>pg_stat_statements</> will appear distinct to a
subsequently executed query that a reasonable observer might judge
to be a non-distinct, if in the interim the table was dropped and
re-created. The hashing process is sensitive to difference in
machine architecture and other facets of the platform.
Furthermore, it is not safe to assume that <structfield>queryid</>
will be stable across major versions of <productname>PostgreSQL</>.
</para>
<para>
As a rule of thumb, an assumption of the stability or comparability
of <structfield>querid</> values should be predicated on the the
underlying catalog metadata and hash function implementation
details exactly matching. Any two servers participating in any
variety of replication based on physical WAL-replay can be expected
to have identical <structfield>querid</> values for the same query.
Logical replication schemes do not have replicas comparable in all
relevant regards, and so <structfield>querid</> will not be a
useful identifier for accumulating costs for the entire replica
set. If in doubt, direct testing is recommended.
</para>
</sect2>

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