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Amazon Redshift
Database Developer Guide (API Version 2012-12-01)

SVL_QUERY_SUMMARY

Use the SVL_QUERY_SUMMARY view to find general information about the execution of a query.

The SVL_QUERY_SUMMARY view contains a subset of data from the SVL_QUERY_REPORT view. Note that the information in SVL_QUERY_SUMMARY is aggregated from all nodes.

Note

The SVL_QUERY_SUMMARY view only contains information about queries executed by Amazon Redshift, not other utility and DDL commands. For a complete listing and information on all statements executed by Amazon Redshift, including DDL and utility commands, you can query the SVL_STATEMENTTEXT view.

SVL_QUERY_SUMMARY 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 user who generated entry.
query integer Query ID. Can be used to join various other system tables and views.
stm integer Stream: A set of concurrent segments in a query. A query has one or more streams.
seg integer Segment number. A query consists of multiple segments, and each segment consists of one or more steps. Query segments can run in parallel. Each segment runs in a single process.
step integer Query step that executed.
maxtime bigint Maximum amount of time for the step to execute (in microseconds).
avgtime bigint Average time for the step to execute (in microseconds).
rows bigint Number of data rows involved in the query step.
bytes bigint Number of data bytes involved in the query step.
rate_row double precision Query execution rate per row.
rate_byte double precision Query execution rate per byte.
label text Step label, which consists of a query step name and, when applicable, table ID and table name (for example, scan tbl=100448 name =user). Three-digit table IDs usually refer to scans of transient tables. When you see tbl=0, it usually refers to a scan of a constant value.
is_diskbased character(1) Whether this step of the query was executed as a disk-based operation on any node in the cluster: true (t) or false (f). Only certain steps, such as hash, sort, and aggregate steps, can go to disk. Many types of steps are always executed in memory.
workmem bigint Amount of working memory (in bytes) assigned to the query step.
is_rrscan character(1) If true (t), indicates that range-restricted scan was used on the step. Default is false (f).
is_delayed_scan character(1) If true (t), indicates that delayed scan was used on the step. Default is false (f).
rows_pre_filter bigint For scans of permanent tables, the total number of rows emitted before filtering rows marked for deletion (ghost rows).

Sample Queries

Viewing Processing Information for a Query Step

The following query shows basic processing information for each step of query 87:

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select query, stm, seg, step, rows, bytes from svl_query_summary where query = 87 order by query, seg, step;

This query retrieves the processing information about query 87, as shown in the following sample output:

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query | stm | seg | step | rows | bytes -------+-----+-----+------+--------+--------- 87 | 0 | 0 | 0 | 90 | 1890 87 | 0 | 0 | 2 | 90 | 360 87 | 0 | 1 | 0 | 90 | 360 87 | 0 | 1 | 2 | 90 | 1440 87 | 1 | 2 | 0 | 210494 | 4209880 87 | 1 | 2 | 3 | 89500 | 0 87 | 1 | 2 | 6 | 4 | 96 87 | 2 | 3 | 0 | 4 | 96 87 | 2 | 3 | 1 | 4 | 96 87 | 2 | 4 | 0 | 4 | 96 87 | 2 | 4 | 1 | 1 | 24 87 | 3 | 5 | 0 | 1 | 24 87 | 3 | 5 | 4 | 0 | 0 (13 rows)

Determining Whether Query Steps Spilled to Disk

The following query shows whether or not any of the steps for the query with query ID 1025 (see the SVL_QLOG view to learn how to obtain the query ID for a query) spilled to disk or if the query ran entirely in-memory:

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select query, step, rows, workmem, label, is_diskbased from svl_query_summary where query = 1025 order by workmem desc;

This query returns the following sample output:

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query| step| rows | workmem | label | is_diskbased -----+-----+--------+-----------+---------------+-------------- 1025 | 0 |16000000| 141557760 |scan tbl=9 | f 1025 | 2 |16000000| 135266304 |hash tbl=142 | t 1025 | 0 |16000000| 128974848 |scan tbl=116536| f 1025 | 2 |16000000| 122683392 |dist | f (4 rows)

By scanning the values for IS_DISKBASED, you can see which query steps went to disk. For query 1025, the hash step ran on disk. Steps might run on disk include hash, aggr, and sort steps. To view only disk-based query steps, add and is_diskbased = 't' clause to the SQL statement in the above example.