STL_SAVE
Contains details for save steps in queries. A save step saves the input stream to a transient table. A transient table is a temporary table that stores intermediate results during query execution.
A query consists of multiple segments, and each segment consists of one or more steps. For more information, see Query processing.
STL_SAVE 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. |
| bytes | bigint | Size, in bytes, of all the output rows for the step. |
| tbl | integer | ID of the materialized transient table. |
| is_diskbased | character(1) | Whether this step of the query was executed as a
disk-based operation: true (t) or false
(f).
|
| workmem | bigint | Number of bytes of working memory assigned to the step. |
Sample queries
The following query shows which save steps in the most recent query were executed on each slice.
select query, slice, segment, step, tasknum, rows, tbl from stl_save where query = pg_last_query_id(); query | slice | segment | step | tasknum | rows | tbl -------+-------+---------+------+---------+------+----- 52236 | 3 | 0 | 2 | 21 | 0 | 239 52236 | 2 | 0 | 2 | 20 | 0 | 239 52236 | 2 | 2 | 2 | 20 | 0 | 239 52236 | 3 | 2 | 2 | 21 | 0 | 239 52236 | 1 | 0 | 2 | 21 | 0 | 239 52236 | 0 | 0 | 2 | 20 | 0 | 239 52236 | 0 | 2 | 2 | 20 | 0 | 239 52236 | 1 | 2 | 2 | 21 | 0 | 239 (8 rows)
