STL_MERGEJOIN
Analyzes merge join execution steps for queries.
This table is visible to all users. Superusers can see all rows; regular users can see only their own data. For more information, see Visibility of Data in System Tables and Views.
Table Columns
| Column Name | Data Type | Description |
|---|---|---|
| userid | integer | ID of the user who generated the entry. |
| query | integer | Query ID. The query column can be used to join other system tables and views. |
| slice | integer | Number that identifies the slice where the query was running. |
| segment | integer | Number that identifies the query segment. |
| step | integer | Query step that executed. |
| starttime | timestamp | Time in UTC that the query started executing, with 6 digits of precision for fractional
seconds. For example: 2009-06-12 11:29:19.131358.
|
| endtime | timestamp | Time in UTC that the query finished executing, with 6 digits of precision for fractional
seconds. For example: 2009-06-12 11:29:19.131358.
|
| tasknum | integer | Number of the query task process that was assigned to execute the step. |
| rows | bigint | Total number of rows that were processed. |
| tbl | integer | Table ID. This is the ID for the inner table that was used in the merge join. |
| checksum | bigint | This information is for internal use only. |
Sample Queries
The following example returns merge join results for the most recent query.
select sum(s.qtysold), e.eventname from event e, listing l, sales s where e.eventid=l.eventid and l.listid= s.listid group by e.eventname; select * from stl_mergejoin where query=pg_last_query_id();
userid | query | slice | segment | step | starttime | endtime | tasknum | rows | tbl --------+-------+-------+---------+------+---------------------+---------------------+---------+------+----- 100 | 27399 | 3 | 4 | 4 | 2013-10-02 16:30:41 | 2013-10-02 16:30:41 | 19 |43428 | 240 100 | 27399 | 0 | 4 | 4 | 2013-10-02 16:30:41 | 2013-10-02 16:30:41 | 19 |43159 | 240 100 | 27399 | 2 | 4 | 4 | 2013-10-02 16:30:41 | 2013-10-02 16:30:41 | 19 |42778 | 240 100 | 27399 | 1 | 4 | 4 | 2013-10-02 16:30:41 | 2013-10-02 16:30:41 | 19 |43091 | 240
