Expose qurey ID in pg_stat_statements view.
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.
This commit is contained in:
Fujii Masao
parent
ef3267523d
commit
91484409bd
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@ -4,8 +4,8 @@ MODULE_big = pg_stat_statements
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OBJS = pg_stat_statements.o
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EXTENSION = pg_stat_statements
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DATA = pg_stat_statements--1.1.sql pg_stat_statements--1.0--1.1.sql \
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pg_stat_statements--unpackaged--1.0.sql
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DATA = pg_stat_statements--1.2.sql pg_stat_statements--1.1--1.2.sql \
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pg_stat_statements--1.0--1.1.sql pg_stat_statements--unpackaged--1.0.sql
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ifdef USE_PGXS
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PG_CONFIG = pg_config
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@ -0,0 +1,43 @@
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/* contrib/pg_stat_statements/pg_stat_statements--1.1--1.2.sql */
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-- complain if script is sourced in psql, rather than via ALTER EXTENSION
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\echo Use "ALTER EXTENSION pg_stat_statements UPDATE TO '1.2'" to load this file. \quit
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/* First we have to remove them from the extension */
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ALTER EXTENSION pg_stat_statements DROP VIEW pg_stat_statements;
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ALTER EXTENSION pg_stat_statements DROP FUNCTION pg_stat_statements();
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/* Then we can drop them */
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DROP VIEW pg_stat_statements;
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DROP FUNCTION pg_stat_statements();
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/* Now redefine */
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CREATE FUNCTION pg_stat_statements(
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OUT userid oid,
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OUT dbid oid,
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OUT queryid bigint,
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OUT query text,
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OUT calls int8,
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OUT total_time float8,
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OUT rows int8,
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OUT shared_blks_hit int8,
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OUT shared_blks_read int8,
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OUT shared_blks_dirtied int8,
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OUT shared_blks_written int8,
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OUT local_blks_hit int8,
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OUT local_blks_read int8,
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OUT local_blks_dirtied int8,
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OUT local_blks_written int8,
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OUT temp_blks_read int8,
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OUT temp_blks_written int8,
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OUT blk_read_time float8,
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OUT blk_write_time float8
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)
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RETURNS SETOF record
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AS 'MODULE_PATHNAME'
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LANGUAGE C;
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CREATE VIEW pg_stat_statements AS
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SELECT * FROM pg_stat_statements();
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GRANT SELECT ON pg_stat_statements TO PUBLIC;
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@ -1,43 +0,0 @@
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/* contrib/pg_stat_statements/pg_stat_statements--1.1.sql */
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-- complain if script is sourced in psql, rather than via CREATE EXTENSION
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\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
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-- Register functions.
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CREATE FUNCTION pg_stat_statements_reset()
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RETURNS void
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AS 'MODULE_PATHNAME'
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LANGUAGE C;
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CREATE FUNCTION pg_stat_statements(
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OUT userid oid,
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OUT dbid oid,
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OUT query text,
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OUT calls int8,
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OUT total_time float8,
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OUT rows int8,
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OUT shared_blks_hit int8,
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OUT shared_blks_read int8,
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OUT shared_blks_dirtied int8,
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OUT shared_blks_written int8,
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OUT local_blks_hit int8,
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OUT local_blks_read int8,
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OUT local_blks_dirtied int8,
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OUT local_blks_written int8,
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OUT temp_blks_read int8,
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OUT temp_blks_written int8,
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OUT blk_read_time float8,
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OUT blk_write_time float8
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)
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RETURNS SETOF record
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AS 'MODULE_PATHNAME'
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LANGUAGE C;
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-- Register a view on the function for ease of use.
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CREATE VIEW pg_stat_statements AS
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SELECT * FROM pg_stat_statements();
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GRANT SELECT ON pg_stat_statements TO PUBLIC;
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-- Don't want this to be available to non-superusers.
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REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;
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@ -0,0 +1,44 @@
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/* contrib/pg_stat_statements/pg_stat_statements--1.2.sql */
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-- complain if script is sourced in psql, rather than via CREATE EXTENSION
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\echo Use "CREATE EXTENSION pg_stat_statements" to load this file. \quit
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-- Register functions.
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CREATE FUNCTION pg_stat_statements_reset()
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RETURNS void
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AS 'MODULE_PATHNAME'
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LANGUAGE C;
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CREATE FUNCTION pg_stat_statements(
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OUT userid oid,
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OUT dbid oid,
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OUT queryid bigint,
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OUT query text,
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OUT calls int8,
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OUT total_time float8,
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OUT rows int8,
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OUT shared_blks_hit int8,
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OUT shared_blks_read int8,
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OUT shared_blks_dirtied int8,
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OUT shared_blks_written int8,
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OUT local_blks_hit int8,
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OUT local_blks_read int8,
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OUT local_blks_dirtied int8,
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OUT local_blks_written int8,
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OUT temp_blks_read int8,
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OUT temp_blks_written int8,
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OUT blk_read_time float8,
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OUT blk_write_time float8
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)
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RETURNS SETOF record
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AS 'MODULE_PATHNAME'
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LANGUAGE C;
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-- Register a view on the function for ease of use.
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CREATE VIEW pg_stat_statements AS
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SELECT * FROM pg_stat_statements();
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GRANT SELECT ON pg_stat_statements TO PUBLIC;
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-- Don't want this to be available to non-superusers.
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REVOKE ALL ON FUNCTION pg_stat_statements_reset() FROM PUBLIC;
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@ -67,7 +67,9 @@ PG_MODULE_MAGIC;
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#define PGSS_DUMP_FILE "global/pg_stat_statements.stat"
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/* This constant defines the magic number in the stats file header */
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static const uint32 PGSS_FILE_HEADER = 0x20120328;
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static const uint32 PGSS_FILE_HEADER = 0x20131115;
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/* PostgreSQL major version number, changes in which invalidate all entries */
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static const uint32 PGSS_PG_MAJOR_VERSION = PG_VERSION_NUM / 100;
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/* XXX: Should USAGE_EXEC reflect execution time and/or buffer usage? */
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#define USAGE_EXEC(duration) (1.0)
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@ -79,6 +81,16 @@ static const uint32 PGSS_FILE_HEADER = 0x20120328;
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#define JUMBLE_SIZE 1024 /* query serialization buffer size */
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/*
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* Extension version number, for supporting older extension versions' objects
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*/
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typedef enum pgssVersion
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{
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PGSS_V1_0 = 0,
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PGSS_V1_1,
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PGSS_V1_2
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} pgssVersion;
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/*
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* Hashtable key that defines the identity of a hashtable entry. We separate
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* queries by user and by database even if they are otherwise identical.
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@ -390,6 +402,7 @@ pgss_shmem_startup(void)
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FILE *file;
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uint32 header;
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int32 num;
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int32 pgver;
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int32 i;
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int query_size;
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int buffer_size;
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@ -465,6 +478,8 @@ pgss_shmem_startup(void)
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if (fread(&header, sizeof(uint32), 1, file) != 1 ||
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header != PGSS_FILE_HEADER ||
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fread(&pgver, sizeof(uint32), 1, file) != 1 ||
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pgver != PGSS_PG_MAJOR_VERSION ||
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fread(&num, sizeof(int32), 1, file) != 1)
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goto error;
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@ -565,6 +580,8 @@ pgss_shmem_shutdown(int code, Datum arg)
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if (fwrite(&PGSS_FILE_HEADER, sizeof(uint32), 1, file) != 1)
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goto error;
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if (fwrite(&PGSS_PG_MAJOR_VERSION, sizeof(uint32), 1, file) != 1)
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goto error;
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num_entries = hash_get_num_entries(pgss_hash);
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if (fwrite(&num_entries, sizeof(int32), 1, file) != 1)
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goto error;
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@ -1069,7 +1086,8 @@ pg_stat_statements_reset(PG_FUNCTION_ARGS)
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}
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#define PG_STAT_STATEMENTS_COLS_V1_0 14
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#define PG_STAT_STATEMENTS_COLS 18
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#define PG_STAT_STATEMENTS_COLS_V1_1 18
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#define PG_STAT_STATEMENTS_COLS 19
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/*
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* Retrieve statement statistics.
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@ -1086,7 +1104,7 @@ pg_stat_statements(PG_FUNCTION_ARGS)
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bool is_superuser = superuser();
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HASH_SEQ_STATUS hash_seq;
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pgssEntry *entry;
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bool sql_supports_v1_1_counters = true;
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pgssVersion detected_version;
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if (!pgss || !pgss_hash)
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ereport(ERROR,
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@ -1107,8 +1125,21 @@ pg_stat_statements(PG_FUNCTION_ARGS)
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/* Build a tuple descriptor for our result type */
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if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
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elog(ERROR, "return type must be a row type");
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if (tupdesc->natts == PG_STAT_STATEMENTS_COLS_V1_0)
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sql_supports_v1_1_counters = false;
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switch (tupdesc->natts)
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{
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case PG_STAT_STATEMENTS_COLS_V1_0:
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detected_version = PGSS_V1_0;
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break;
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case PG_STAT_STATEMENTS_COLS_V1_1:
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detected_version = PGSS_V1_1;
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break;
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case PG_STAT_STATEMENTS_COLS:
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detected_version = PGSS_V1_2;
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break;
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default:
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elog(ERROR, "pgss version unrecognized from tuple descriptor");
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}
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per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
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oldcontext = MemoryContextSwitchTo(per_query_ctx);
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@ -1140,6 +1171,9 @@ pg_stat_statements(PG_FUNCTION_ARGS)
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{
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char *qstr;
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if (detected_version >= PGSS_V1_2)
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values[i++] = Int64GetDatumFast((int64) entry->key.queryid);
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qstr = (char *)
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pg_do_encoding_conversion((unsigned char *) entry->query,
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entry->query_len,
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@ -1150,7 +1184,12 @@ pg_stat_statements(PG_FUNCTION_ARGS)
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pfree(qstr);
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}
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else
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{
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if (detected_version >= PGSS_V1_2)
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nulls[i++] = true;
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values[i++] = CStringGetTextDatum("<insufficient privilege>");
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}
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/* copy counters to a local variable to keep locking time short */
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{
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@ -1170,24 +1209,27 @@ pg_stat_statements(PG_FUNCTION_ARGS)
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values[i++] = Int64GetDatumFast(tmp.rows);
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values[i++] = Int64GetDatumFast(tmp.shared_blks_hit);
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values[i++] = Int64GetDatumFast(tmp.shared_blks_read);
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if (sql_supports_v1_1_counters)
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if (detected_version >= PGSS_V1_1)
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values[i++] = Int64GetDatumFast(tmp.shared_blks_dirtied);
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values[i++] = Int64GetDatumFast(tmp.shared_blks_written);
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values[i++] = Int64GetDatumFast(tmp.local_blks_hit);
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values[i++] = Int64GetDatumFast(tmp.local_blks_read);
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if (sql_supports_v1_1_counters)
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if (detected_version >= PGSS_V1_1)
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values[i++] = Int64GetDatumFast(tmp.local_blks_dirtied);
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values[i++] = Int64GetDatumFast(tmp.local_blks_written);
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values[i++] = Int64GetDatumFast(tmp.temp_blks_read);
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values[i++] = Int64GetDatumFast(tmp.temp_blks_written);
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if (sql_supports_v1_1_counters)
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if (detected_version >= PGSS_V1_1)
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{
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values[i++] = Float8GetDatumFast(tmp.blk_read_time);
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values[i++] = Float8GetDatumFast(tmp.blk_write_time);
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}
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Assert(i == (sql_supports_v1_1_counters ?
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PG_STAT_STATEMENTS_COLS : PG_STAT_STATEMENTS_COLS_V1_0));
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Assert(i == (detected_version == PGSS_V1_0?
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PG_STAT_STATEMENTS_COLS_V1_0:
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detected_version == PGSS_V1_1?
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PG_STAT_STATEMENTS_COLS_V1_1:
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PG_STAT_STATEMENTS_COLS));
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tuplestore_putvalues(tupstore, tupdesc, values, nulls);
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}
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@ -1,5 +1,5 @@
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# pg_stat_statements extension
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comment = 'track execution statistics of all SQL statements executed'
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default_version = '1.1'
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default_version = '1.2'
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module_pathname = '$libdir/pg_stat_statements'
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relocatable = true
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@ -23,11 +23,12 @@
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<title>The <structname>pg_stat_statements</structname> View</title>
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<para>
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The statistics gathered by the module are made available via a system view
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named <structname>pg_stat_statements</>. This view contains one row for
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each distinct query, database ID, and user ID (up to the maximum
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number of distinct statements that the module can track). The columns
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of the view are shown in <xref linkend="pgstatstatements-columns">.
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The statistics gathered by the module are made available via a
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system view named <structname>pg_stat_statements</>. This view
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contains one row for each distinct database ID, user ID and query
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ID (up to the maximum number of distinct statements that the module
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can track). The columns of the view are shown in
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<xref linkend="pgstatstatements-columns">.
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</para>
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<table id="pgstatstatements-columns">
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@ -57,7 +58,14 @@
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<entry>OID of database in which the statement was executed</entry>
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</row>
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<row>
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<row>
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<entry><structfield>queryid</structfield></entry>
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<entry><type>bigint</type></entry>
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<entry></entry>
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<entry>Internal hash identifier, computed from the entry's post-parse-analysis tree</entry>
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</row>
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<row>
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<entry><structfield>query</structfield></entry>
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<entry><type>text</type></entry>
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<entry></entry>
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@ -189,9 +197,10 @@
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</para>
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<para>
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For security reasons, non-superusers are not allowed to see the text of
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queries executed by other users. They can see the statistics, however,
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if the view has been installed in their database.
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For security reasons, non-superusers are not allowed to see the SQL
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text or queryid of queries executed by other users. They can see
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the statistics, however, if the view has been installed in their
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database.
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</para>
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<para>
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@ -209,8 +218,9 @@
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When a constant's value has been ignored for purposes of matching the
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query to other queries, the constant is replaced by <literal>?</literal>
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in the <structname>pg_stat_statements</> display. The rest of the query
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text is that of the first query that had the particular hash value
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associated with the <structname>pg_stat_statements</> entry.
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text is that of the first query that had the particular
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<structfield>queryid</> hash value associated with the
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<structname>pg_stat_statements</> entry.
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</para>
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<para>
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@ -223,10 +233,45 @@
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</para>
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<para>
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Since the hash value is computed on the post-parse-analysis representation
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of the queries, the opposite is also possible: queries with identical texts
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might appear as separate entries, if they have different meanings as a
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result of factors such as different <varname>search_path</> settings.
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Since the <structfield>queryid</> hash value is computed on the
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post-parse-analysis representation of the queries, the opposite is
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also possible: queries with identical texts might appear as
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separate entries, if they have different meanings as a result of
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factors such as different <varname>search_path</> settings.
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</para>
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<para>
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Consumers of <literal>pg_stat_statements</> may wish to use
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<structfield>queryid</> (perhaps in composite with
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<structfield>dbid</> and <structfield>userid</>) as a more stable
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and reliable identifier for each entry than its query text.
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However, it is important to understand that there are only limited
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guarantees around the stability of the <structfield>queryid</> hash
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value. Since the identifier is derived from the
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post-parse-analysis tree, its value is a function of, among other
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things, the internal identifiers that comprise this representation.
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This has some counterintuitive implications. For example, a query
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against a table that is fingerprinted by
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<literal>pg_stat_statements</> will appear distinct to a
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subsequently executed query that a reasonable observer might judge
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to be a non-distinct, if in the interim the table was dropped and
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re-created. The hashing process is sensitive to difference in
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machine architecture and other facets of the platform.
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Furthermore, it is not safe to assume that <structfield>queryid</>
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will be stable across major versions of <productname>PostgreSQL</>.
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</para>
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<para>
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As a rule of thumb, an assumption of the stability or comparability
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of <structfield>querid</> values should be predicated on the the
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underlying catalog metadata and hash function implementation
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details exactly matching. Any two servers participating in any
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variety of replication based on physical WAL-replay can be expected
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to have identical <structfield>querid</> values for the same query.
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Logical replication schemes do not have replicas comparable in all
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relevant regards, and so <structfield>querid</> will not be a
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useful identifier for accumulating costs for the entire replica
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set. If in doubt, direct testing is recommended.
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</para>
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</sect2>
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