.show extents
Applies to: ✅ Azure Data Explorer
Note
Data shards are called extents, and all commands use "extent" or "extents" as a synonym. For more information on extents, see Extents (Data Shards) Overview.
The types of .show extents commands are as follows:
- Show some or all extents for a specific table scope
- Show some or all extents for a specific database scope
- Show some or all extents for the entire cluster
Note
The .show extents command may consume a lot of resources if it runs on a scope
(such as a database or a cluster) with many extents. We recommended
using the command variant at the lowest possible scope. Table-scope
is preferable over database-scope, and database-scope over cluster-scope. The
command variant that includes filtering extents is preferable to filtering the results
of the command using another query.
Permissions
To see extents on the cluster, you must have AllDatabasesMonitor permissions.
To see extents on a database, you must have Database User, Database Viewer, or Database Monitor permissions.
For more information, see role-based access control.
Table scope
Syntax
Shows information about extents (data shards) that are present in the specified tables. The database is taken from the command's context.
If hot is specified, shows only extents that are expected to be in the hot cache.
.show table TableName extents [( ExtentId [, ...])] [hot] [where tags (has|contains|!has|!contains) TagName [and tags (has|contains|!has|!contains) TagName [, ...]]]
.show tables (TableName [, ...]) extents [( ExtentId [, ...])] [hot] [where tags (has|contains|!has|!contains) TagName [and tags (has|contains|!has|!contains) TagName [, ...]]]
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| TableName | string |
✔️ | The name of the table. |
| ExtentId | string |
The ID of the extent to show. | |
| Tag | string |
The name of a tag to filter by as specified. |
Recommendations
- Using built-in filtering capabilities in the command is preferred over adding
a query-based filter (such as adding
| where DatabaseName == '...'andTableName == '...'). - If the optional list of extent IDs is provided, the returned dataset is limited to those extents only.
- This method is faster than filtering (adding
| where ExtentId in(...)) to the results of "bare" commands.
- This method is faster than filtering (adding
- If
tagsfilters are specified:- The returned list is limited to those extents whose tags collection obeys all of the provided tags filters.
- This method is faster than filtering (adding
| where Tags has '...' and Tags contains '...'to) the results of "bare" commands. hasfilters are equality filters. Extents that aren't tagged with either of the specified tags are filtered out.!hasfilters are equality negative filters. Extents that are tagged with either of the specified tags are filtered out.containsfilters are case-insensitive substring filters. Extents that don't have the specified strings as a substring of any of their tags are filtered out.!containsfilters are case-insensitive substring negative filters. Extents that have the specified strings as a substring of any of their tags are filtered out.
Database scope
Shows information about extents (data shards) that are present in the specified database.
If hot is specified - shows only extents that expected to be in the hot cache.
Syntax
.show database DatabaseName extents [( ExtentId [, ...])] [hot] [where tags (has|contains|!has|!contains) TagName [and tags (has|contains|!has|!contains) TagName [, ...]]]
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| DatabaseName | string |
✔️ | The name of the database. |
| ExtentId | string |
The ID of the extent to show. | |
| Tag | string |
The name of a tag to filter by as specified. |
Cluster scope
Syntax
.show cluster extents [hot]
Learn more about syntax conventions.
Shows information about extents (data shards) that are present in the cluster.
If hot is specified - shows only extents that are expected to be in the hot cache.
Returns
| Output parameter | Type | Description |
|---|---|---|
| ExtentId | guid |
ID of the extent |
| DatabaseName | string |
Database that the extent belongs to. |
| TableName | string |
Table that the extents belong to. |
| MaxCreatedOn | datetime |
Date-time when the extent was created. For a merged extent, the maximum of creation times among source extents. |
| OriginalSize | Double | Original size in bytes of the extent data. |
| ExtentSize | Double | Size of the extent in memory (compressed + index). |
| CompressedSize | Double | Compressed size of the extent data in memory. |
| IndexSize | Double | Index size of the extent data. |
| Blocks | long |
Number of data blocks in the extent. |
| Segments | long |
Number of data segments in the extent. |
| ExtentContainerId | string |
ID of the extent container the extent is in. |
| RowCount | long |
Number of rows in the extent. |
| MinCreatedOn | datetime |
Date-time when the extent was created. For a merged extent, the minimum of creation times among the source extents. |
| Tags | string |
Tags, if any, defined for the extent. |
| Kind | string |
The kind of the storage engine that created the extent. |
| DeletedRowCount | long |
Number of deleted rows in the extent. |
Examples
Tagged extent
Extent E in table T is tagged with tags aaa, BBB, and ccc.
This query returns
E:.show table T extents where tags has 'aaa' and tags contains 'bb'This query doesn't return
Esince it isn't tagged withaa:.show table T extents where tags has 'aa' and tags contains 'bb'This query returns
E:.show table T extents where tags contains 'aaa' and tags contains 'bb'
Show volume of extents created
Show volume of extents being created per hour in a specific database
.show database MyDatabase extents | summarize count(ExtentId) by MaxCreatedOn bin=time(1h) | render timechart
Show volume of data arriving by table per hour
.show database MyDatabase extents
| summarize sum(OriginalSize) by TableName, MaxCreatedOn bin=time(1h)
| render timechart
Show data size distribution by table
.show database MyDatabase extents | summarize sum(OriginalSize) by TableName
Show all extents in the database named 'GamesDB'
.show database GamesDB extents
Show all extents in the table named 'Games'
.show table Games extents
Show all extents in specific tables
Show all extents in the tables named 'TaggingGames1' and 'TaggingGames2', tagged with both 'tag1' and 'tag2'
.show tables (TaggingGames1,TaggingGames2) extents where tags has 'tag1' and tags has 'tag2'