UNSPLIT AT

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The UNSPLIT AT statement removes a split enforcement on a range split, at a specified row in a table or index. UNSPLIT ALL removes all split enforcements for a table or index.

Removing a split enforcement from a table or index ("unsplitting") allows CockroachDB to merge ranges as needed, to help improve your cluster's performance. For more information, see Range Merges.

Synopsis

ALTER TABLE table_name UNSPLIT AT select_stmt ALL
ALTER INDEX table_name @ index_name UNSPLIT AT select_stmt ALL

Required privileges

The user must have the INSERT privilege on the table or index.

Parameters

Parameter Description
table_name The name of the table to unsplit.
table_name @ index_name
standalone_index_name
The name of the index to unsplit.
select_stmt A selection query that produces one or more rows at which to unsplit a table or index.

Examples

Setup

The following examples use MovR, a fictional vehicle-sharing application, to demonstrate CockroachDB SQL statements. For more information about the MovR example application and dataset, see MovR: A Global Vehicle-sharing App.

To follow along, run cockroach demo with the --geo-partitioned-replicas flag. This command opens an interactive SQL shell to a temporary, 9-node in-memory cluster with the movr database.

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$ cockroach demo --geo-partitioned-replicas

Unsplit a table

Create a drivers table and split the table based on the compound primary key as described in Split a table with a compound primary key.

To remove the split enforcements, run the following:

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> ALTER TABLE drivers UNSPLIT AT VALUES ('new york', '3'), ('new york', '7'), ('chicago', '3'), ('chicago', '7'), ('seattle', '3'), ('seattle', '7');
                     key                    |           pretty
--------------------------------------------+-----------------------------
  \xc3\x89\x12new york\x00\x01\x123\x00\x01 | /Table/59/1/"new york"/"3"
  \xc3\x89\x12new york\x00\x01\x127\x00\x01 | /Table/59/1/"new york"/"7"
  \xc3\x89\x12chicago\x00\x01\x123\x00\x01  | /Table/59/1/"chicago"/"3"
  \xc3\x89\x12chicago\x00\x01\x127\x00\x01  | /Table/59/1/"chicago"/"7"
  \xc3\x89\x12seattle\x00\x01\x123\x00\x01  | /Table/59/1/"seattle"/"3"
  \xc3\x89\x12seattle\x00\x01\x127\x00\x01  | /Table/59/1/"seattle"/"7"
(6 rows)

You can see the split's expiration date in the split_enforced_until column. The crdb_internal.ranges table also contains information about ranges in your CockroachDB cluster, including the split_enforced_until column.

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> SELECT range_id, start_pretty, end_pretty, split_enforced_until FROM crdb_internal.ranges WHERE table_name='drivers';
  range_id |        start_pretty        |         end_pretty         | split_enforced_until
-----------+----------------------------+----------------------------+-----------------------
        74 | /Table/59                  | /Table/59/1/"chicago"/"3"  | NULL
        77 | /Table/59/1/"chicago"/"3"  | /Table/59/1/"chicago"/"7"  | NULL
        78 | /Table/59/1/"chicago"/"7"  | /Table/59/1/"new york"/"3" | NULL
        75 | /Table/59/1/"new york"/"3" | /Table/59/1/"new york"/"7" | NULL
        76 | /Table/59/1/"new york"/"7" | /Table/59/1/"seattle"/"3"  | NULL
        79 | /Table/59/1/"seattle"/"3"  | /Table/59/1/"seattle"/"7"  | NULL
        80 | /Table/59/1/"seattle"/"7"  | /Max                       | NULL
(7 rows)

The drivers table is still split into ranges at specific primary key column values, but the split_enforced_until column is now NULL for all ranges in the table. The split is no longer enforced, and CockroachDB can merge the data in the table as needed.

Unsplit an index

Add a new secondary index to the rides table, on the revenue column, and then split the table ranges by secondary index values as described in Split an index.

To remove the split enforcements, run the following:

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> ALTER INDEX rides@revenue_idx UNSPLIT AT VALUES (25.00), (50.00), (75.00);
         key        |      pretty
--------------------+-------------------
  \277\214*2\000    | /Table/55/4/25
  \277\214*d\000    | /Table/55/4/5E+1
  \277\214*\226\000 | /Table/55/4/75
(3 rows)

You can see the split's expiration date in the split_enforced_until column. The crdb_internal.ranges table also contains information about ranges in your CockroachDB cluster, including the split_enforced_until column.

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> SELECT range_id, start_pretty, end_pretty, split_enforced_until FROM crdb_internal.ranges WHERE table_name='rides';
  range_id |                                        start_pretty                                         |                                         end_pretty                                          |        split_enforced_until
-----------+---------------------------------------------------------------------------------------------+---------------------------------------------------------------------------------------------+--------------------------------------
        39 | /Table/55                                                                                   | /Table/55/1/"amsterdam"/"\xc5\x1e\xb8Q\xeb\x85@\x00\x80\x00\x00\x00\x00\x00\x01\x81"        | NULL
        56 | /Table/55/1/"amsterdam"/"\xc5\x1e\xb8Q\xeb\x85@\x00\x80\x00\x00\x00\x00\x00\x01\x81"        | /Table/55/1/"boston"/"8Q\xeb\x85\x1e\xb8B\x00\x80\x00\x00\x00\x00\x00\x00n"                 | 2262-04-11 23:47:16.854776+00:00:00
        55 | /Table/55/1/"boston"/"8Q\xeb\x85\x1e\xb8B\x00\x80\x00\x00\x00\x00\x00\x00n"                 | /Table/55/1/"los angeles"/"\xa8\xf5\u008f\\(H\x00\x80\x00\x00\x00\x00\x00\x01J"             | 2262-04-11 23:47:16.854776+00:00:00
        53 | /Table/55/1/"los angeles"/"\xa8\xf5\u008f\\(H\x00\x80\x00\x00\x00\x00\x00\x01J"             | /Table/55/1/"new york"/"\x1c(\xf5\u008f\\I\x00\x80\x00\x00\x00\x00\x00\x007"                | 2262-04-11 23:47:16.854776+00:00:00
        66 | /Table/55/1/"new york"/"\x1c(\xf5\u008f\\I\x00\x80\x00\x00\x00\x00\x00\x007"                | /Table/55/1/"paris"/"\xe1G\xae\x14z\xe1H\x00\x80\x00\x00\x00\x00\x00\x01\xb8"               | 2262-04-11 23:47:16.854776+00:00:00
        52 | /Table/55/1/"paris"/"\xe1G\xae\x14z\xe1H\x00\x80\x00\x00\x00\x00\x00\x01\xb8"               | /Table/55/1/"san francisco"/"\x8c\xcc\xcc\xcc\xcc\xcc@\x00\x80\x00\x00\x00\x00\x00\x01\x13" | 2262-04-11 23:47:16.854776+00:00:00
        65 | /Table/55/1/"san francisco"/"\x8c\xcc\xcc\xcc\xcc\xcc@\x00\x80\x00\x00\x00\x00\x00\x01\x13" | /Table/55/1/"seattle"/"p\xa3\xd7\n=pD\x00\x80\x00\x00\x00\x00\x00\x00\xdc"                  | 2262-04-11 23:47:16.854776+00:00:00
        64 | /Table/55/1/"seattle"/"p\xa3\xd7\n=pD\x00\x80\x00\x00\x00\x00\x00\x00\xdc"                  | /Table/55/1/"washington dc"/"Tz\xe1G\xae\x14L\x00\x80\x00\x00\x00\x00\x00\x00\xa5"          | 2262-04-11 23:47:16.854776+00:00:00
        54 | /Table/55/1/"washington dc"/"Tz\xe1G\xae\x14L\x00\x80\x00\x00\x00\x00\x00\x00\xa5"          | /Table/55/4                                                                                 | 2262-04-11 23:47:16.854776+00:00:00
        68 | /Table/55/4                                                                                 | /Table/55/4/25                                                                              | 2021-04-08 16:27:45.201336+00:00:00
        69 | /Table/55/4/25                                                                              | /Table/55/4/5E+1                                                                            | NULL
        70 | /Table/55/4/5E+1                                                                            | /Table/55/4/75                                                                              | NULL
        71 | /Table/55/4/75                                                                              | /Table/56                                                                                   | NULL
(13 rows)

The table is still split into ranges at 25.00, 50.00, and 75.00, but the split_enforced_until column is now NULL for all ranges in the table. The split is no longer enforced, and CockroachDB can merge the data in the table as needed.

See also


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