SHOW META [ LIKE pattern ]SHOW META is an SQL statement that displays extra meta-information about the processed query, including query time and keyword statistics. The syntax is:
SELECT id,story_author FROM hn_small WHERE MATCH('one|two|three') limit 5;
SHOW META;+--------+--------------+
| id | story_author |
+--------+--------------+
| 300263 | throwaway37 |
| 713503 | mahmud |
| 716804 | mahmud |
| 776906 | jimbokun |
| 753332 | foxhop |
+--------+--------------+
5 rows in set (0.01 sec)
+----------------+--------+
| Variable_name | Value |
+----------------+--------+
| total | 5 |
| total_found | 266385 |
| total_relation | eq |
| time | 0.012 |
| keyword[0] | one |
| docs[0] | 224387 |
| hits[0] | 310327 |
| keyword[1] | three |
| docs[1] | 18181 |
| hits[1] | 21102 |
| keyword[2] | two |
| docs[2] | 63251 |
| hits[2] | 75961 |
+----------------+--------+
13 rows in set (0.00 sec)SHOW META can display I/O and CPU counters, but they will only be available if searchd was started with the --iostats and --cpustats switches, respectively.
SELECT id,channel_id FROM records WHERE MATCH('one|two|three') limit 5;
SHOW META;+--------+--------------+
| id | story_author |
+--------+--------------+
| 300263 | throwaway37 |
| 713503 | mahmud |
| 716804 | mahmud |
| 776906 | jimbokun |
| 753332 | foxhop |
+--------+--------------+
5 rows in set (0.01 sec)
+-----------------------+--------+
| Variable_name | Value |
+-----------------------+--------+
| total | 5 |
| total_found | 266385 |
| total_relation | eq |
| time | 0.011 |
| cpu_time | 18.004 |
| agents_cpu_time | 0.000 |
| io_read_time | 0.000 |
| io_read_ops | 0 |
| io_read_kbytes | 0.0 |
| io_write_time | 0.000 |
| io_write_ops | 0 |
| io_write_kbytes | 0.0 |
| agent_io_read_time | 0.000 |
| agent_io_read_ops | 0 |
| agent_io_read_kbytes | 0.0 |
| agent_io_write_time | 0.000 |
| agent_io_write_ops | 0 |
| agent_io_write_kbytes | 0.0 |
| keyword[0] | one |
| docs[0] | 224387 |
| hits[0] | 310327 |
| keyword[1] | three |
| docs[1] | 18181 |
| hits[1] | 21102 |
| keyword[2] | two |
| docs[2] | 63251 |
| hits[2] | 75961 |
+-----------------------+--------+
27 rows in set (0.00 sec)Additional values, such as predicted_time, dist_predicted_time, local_fetched_docs, local_fetched_hits, local_fetched_skips, and their respective dist_fetched_* counterparts, will only be available if searchd was configured with predicted time costs and the query included predicted_time in the OPTION clause.
SELECT id,story_author FROM hn_small WHERE MATCH('one|two|three') limit 5 option max_predicted_time=100;
SHOW META;+--------+--------------+
| id | story_author |
+--------+--------------+
| 300263 | throwaway37 |
| 713503 | mahmud |
| 716804 | mahmud |
| 776906 | jimbokun |
| 753332 | foxhop |
+--------+--------------+
5 rows in set (0.01 sec)
mysql> show meta;
+---------------------+--------+
| Variable_name | Value |
+---------------------+--------+
| total | 5 |
| total_found | 266385 |
| total_relation | eq |
| time | 0.012 |
| local_fetched_docs | 307212 |
| local_fetched_hits | 407390 |
| local_fetched_skips | 24 |
| predicted_time | 56 |
| keyword[0] | one |
| docs[0] | 224387 |
| hits[0] | 310327 |
| keyword[1] | three |
| docs[1] | 18181 |
| hits[1] | 21102 |
| keyword[2] | two |
| docs[2] | 63251 |
| hits[2] | 75961 |
+---------------------+--------+
17 rows in set (0.00 sec)SHOW META must be executed immediately after the query in the same session. Since some MySQL connectors/libraries use connection pools, running SHOW META in a separate statement can lead to unexpected results, such as retrieving metadata from another query. In these cases (and generally recommended), run a multiple statement containing both the query and SHOW META. Some connectors/libraries support multi-queries within the same method for a single statement, while others may require the use of a dedicated method for multi-queries or setting specific options during connection setup.
SELECT id,story_author FROM hn_small WHERE MATCH('one|two|three') LIMIT 5; SHOW META;+--------+--------------+
| id | story_author |
+--------+--------------+
| 300263 | throwaway37 |
| 713503 | mahmud |
| 716804 | mahmud |
| 776906 | jimbokun |
| 753332 | foxhop |
+--------+--------------+
5 rows in set (0.01 sec)
+----------------+--------+
| Variable_name | Value |
+----------------+--------+
| total | 5 |
| total_found | 266385 |
| total_relation | eq |
| time | 0.011 |
| keyword[0] | one |
| docs[0] | 224387 |
| hits[0] | 310327 |
| keyword[1] | three |
| docs[1] | 18181 |
| hits[1] | 21102 |
| keyword[2] | two |
| docs[2] | 63251 |
| hits[2] | 75961 |
+----------------+--------+
13 rows in set (0.00 sec)You can also use the optional LIKE clause, which allows you to select only the variables that match a specific pattern. The pattern syntax follows standard SQL wildcards, where % represents any number of any characters, and _ represents a single character.
SHOW META LIKE 'total%';+----------------+--------+
| Variable_name | Value |
+----------------+--------+
| total | 5 |
| total_found | 266385 |
| total_relation | eq |
+----------------+--------+
3 rows in set (0.00 sec)When utilizing faceted search, you can examine the multiplier field in the SHOW META output to determine how many queries were executed in an optimized group.
SELECT * FROM facetdemo FACET brand_id FACET price FACET categories;
SHOW META LIKE 'multiplier';+------+-------+----------+---------------------+-------------+-------------+---------------------------------------+------------+
| id | price | brand_id | title | brand_name | property | j | categories |
+------+-------+----------+---------------------+-------------+-------------+---------------------------------------+------------+
| 1 | 306 | 1 | Product Ten Three | Brand One | Six_Ten | {"prop1":66,"prop2":91,"prop3":"One"} | 10,11 |
...
+----------+----------+
| brand_id | count(*) |
+----------+----------+
| 1 | 1013 |
...
+-------+----------+
| price | count(*) |
+-------+----------+
| 306 | 7 |
...
+------------+----------+
| categories | count(*) |
+------------+----------+
| 10 | 2436 |
...
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| multiplier | 4 |
+---------------+-------+
1 row in set (0.00 sec)When the cost-based query optimizer chooses to use DocidIndex, ColumnarScan, or SecondaryIndex instead of a plain filter, this is reflected in the SHOW META command.
The index variable displays the names and types of secondary indexes used during query execution. The percentage indicates how many disk chunks (in the case of an RT index) or pseudo shards (in the case of a plain index) utilized the secondary index.
SELECT count(*) FROM taxi1 WHERE tip_amount = 5;
SHOW META;+----------------+----------------------------------+
| Variable_name | Value |
+----------------+----------------------------------+
| total | 1 |
| total_found | 1 |
| total_relation | eq |
| time | 0.016 |
| index | tip_amount:SecondaryIndex (100%) |
+----------------+----------------------------------+
5 rows in set (0.00 sec)SHOW META can be used after executing a CALL PQ statement, in which case it provides different output.
SHOW META following a CALL PQ statement includes:
Total - Total time spent on matching the document(s)Queries matched - Number of stored queries that match the document(s)Document matches - Number of documents that matched the queries stored in the tableTotal queries stored - Total number of queries stored in the tableTerm only queries - Number of queries in the table that have terms; the remaining queries use extended query syntax.CALL PQ ('pq', ('{"title":"angry", "gid":3 }')); SHOW META;+------+
| id |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
+-----------------------+-----------+
| Name | Value |
+-----------------------+-----------+
| Total | 0.000 sec |
| Queries matched | 1 |
| Queries failed | 0 |
| Document matched | 1 |
| Total queries stored | 2 |
| Term only queries | 2 |
| Fast rejected queries | 1 |
+-----------------------+-----------+
7 rows in set (0.00 sec)Using CALL PQ with a verbose option provides more detailed output.
It includes the following additional entries:
Setup - Time spent on the initial setup of the matching process, such as parsing docs and setting optionsQueries failed - Number of queries that failedFast rejected queries - Number of queries that were not fully evaluated but quickly matched and rejected using filters or other conditionsTime per query - Detailed time for each queryTime of matched queries - Total time spent on queries that matched any documentsCALL PQ ('pq', ('{"title":"angry", "gid":3 }'), 1 as verbose); SHOW META;+------+
| id |
+------+
| 2 |
+------+
1 row in set (0.00 sec)
+-------------------------+-----------+
| Name | Value |
+-------------------------+-----------+
| Total | 0.000 sec |
| Setup | 0.000 sec |
| Queries matched | 1 |
| Queries failed | 0 |
| Document matched | 1 |
| Total queries stored | 2 |
| Term only queries | 2 |
| Fast rejected queries | 1 |
| Time per query | 69 |
| Time of matched queries | 69 |
+-------------------------+-----------+
10 rows in set (0.00 sec)