This page lists the experimental features that are available in CockroachDB v19.2.
This page describes experimental features. Their interfaces and outputs are subject to change, and there may be bugs.
If you encounter a bug, please file an issue.
Session variables
The table below lists the experimental session settings that are available. For a complete list of session variables, see SHOW (session settings).
| Variable | Default Value | Description |
|---|---|---|
experimental_force_split_at |
'off' |
Indicates whether checks to prevent incorrect usage of ALTER TABLE ... SPLIT AT should be skipped. |
experimental_serial_normalization |
'rowid' |
If set to 'virtual_sequence', make the SERIAL pseudo-type optionally auto-create a sequence for better compatibility with Hibernate sequences. |
SQL statements
Keep SQL audit logs
Log all queries against a table to a file, for security purposes. For more information, see ALTER TABLE ... EXPERIMENTAL_AUDIT.
> ALTER TABLE t EXPERIMENTAL_AUDIT SET READ WRITE;
Relocate leases and replicas
You have the following options for controlling lease and replica location:
- Relocate leases and replicas using
EXPERIMENTAL_RELOCATE - Relocate just leases using
EXPERIMENTAL_RELOCATE LEASE
For example, to distribute leases and ranges for N primary keys across N stores in the cluster, run a statement with the following structure:
> ALTER TABLE t EXPERIMENTAL_RELOCATE SELECT ARRAY[<storeid1>, <storeid2>, ..., <storeidN>], <primarykeycol1>, <primarykeycol2>, ..., <primarykeycolN>;
To relocate just the lease without moving the replicas, run a statement like the one shown below, which moves the lease for the range containing primary key 'foo' to store 1.
> ALTER TABLE t EXPERIMENTAL_RELOCATE LEASE SELECT 1, 'foo';
Show table fingerprints
Table fingerprints are used to compute an identification string of an entire table, for the purpose of gauging whether two tables have the same data. This is useful, for example, when restoring a table from backup.
Example:
> SHOW EXPERIMENTAL_FINGERPRINTS FROM TABLE t;
index_name | fingerprint
------------+---------------------
primary | 1999042440040364641
(1 row)
Turn on KV event tracing
Use session tracing (via SHOW TRACE FOR SESSION) to report the replicas of all KV events that occur during its execution.
Example:
> SET tracing = on;
> SELECT * from t;
> SET tracing = off;
> SHOW EXPERIMENTAL_REPLICA TRACE FOR SESSION;
timestamp | node_id | store_id | replica_id
----------------------------------+---------+----------+------------
2018-10-18 15:50:13.345879+00:00 | 3 | 3 | 7
2018-10-18 15:50:20.628383+00:00 | 2 | 2 | 26
Check for constraint violations with SCRUB
Checks the consistency of UNIQUE indexes, CHECK constraints, and more. Partially implemented; see cockroachdb/cockroach#10425 for details.
This example uses the users table from our open-source, fictional peer-to-peer vehicle-sharing application, MovR.
> EXPERIMENTAL SCRUB table movr.users;
job_uuid | error_type | database | table | primary_key | timestamp | repaired | details
----------+--------------------------+----------+-------+----------------------------------------------------------+---------------------------+----------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| index_key_decoding_error | movr | users | ('boston','0009eeb5-d779-4bf8-b1bd-8566533b105c') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'06484 Christine Villages\\nGrantport, TN 01572'", "city": "'boston'", "credit_card": "'4634253150884'", "id": "'0009eeb5-d779-4bf8-b1bd-8566533b105c'", "name": "'Jessica Webb'"}}
| index_key_decoding_error | movr | users | ('los angeles','0001252c-fc16-4006-b6dc-c6b1a0fd1f5b') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'91309 Warner Springs\\nLake Danielmouth, PR 33400'", "city": "'los angeles'", "credit_card": "'3584736360686445'", "id": "'0001252c-fc16-4006-b6dc-c6b1a0fd1f5b'", "name": "'Rebecca Gibson'"}}
| index_key_decoding_error | movr | users | ('new york','000169a5-e337-4441-b664-dae63e682980') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'0787 Christopher Highway Apt. 363\\nHamptonmouth, TX 91864-2620'", "city": "'new york'", "credit_card": "'4578562547256688'", "id": "'000169a5-e337-4441-b664-dae63e682980'", "name": "'Christopher Johnson'"}}
| index_key_decoding_error | movr | users | ('paris','00089fc4-e5b1-48f6-9f0b-409905f228c4') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'46735 Martin Summit\\nMichaelview, OH 10906-5889'", "city": "'paris'", "credit_card": "'5102207609888778'", "id": "'00089fc4-e5b1-48f6-9f0b-409905f228c4'", "name": "'Nicole Fuller'"}}
| index_key_decoding_error | movr | users | ('rome','000209fc-69a1-4dd5-8053-3b5e5769876d') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'473 Barrera Vista Apt. 890\\nYeseniaburgh, CO 78087'", "city": "'rome'", "credit_card": "'3534605564661093'", "id": "'000209fc-69a1-4dd5-8053-3b5e5769876d'", "name": "'Sheryl Shea'"}}
| index_key_decoding_error | movr | users | ('san francisco','00058767-1e83-4e18-999f-13b5a74d7225') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'5664 Acevedo Drive Suite 829\\nHernandezview, MI 13516'", "city": "'san francisco'", "credit_card": "'376185496850202'", "id": "'00058767-1e83-4e18-999f-13b5a74d7225'", "name": "'Kevin Turner'"}}
| index_key_decoding_error | movr | users | ('seattle','0002e904-1256-4528-8b5f-abad16e695ff') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'81499 Samuel Crescent Suite 631\\nLake Christopherborough, PR 50401'", "city": "'seattle'", "credit_card": "'38743493725890'", "id": "'0002e904-1256-4528-8b5f-abad16e695ff'", "name": "'Mark Williams'"}}
| index_key_decoding_error | movr | users | ('washington dc','00007caf-2014-4696-85b0-840e7d8b6db9') | 2018-10-18 16:00:38.65916 | f | {"error_message": "key ordering did not match datum ordering. IndexDescriptor=ASC", "index_name": "primary", "row_data": {"address": "e'4578 Holder Trafficway\\nReynoldsside, IL 23520-7418'", "city": "'washington dc'", "credit_card": "'30454993082943'", "id": "'00007caf-2014-4696-85b0-840e7d8b6db9'", "name": "'Marie Miller'"}}
(8 rows)
Show range information for a specific row
The SHOW RANGE ... FOR ROW statement shows information about a range for a particular row of data. This information is useful for verifying how SQL data maps to underlying ranges, and where the replicas for a range are located.
Functions and Operators
The table below lists the experimental SQL functions and operators available in CockroachDB. For more information, see each function's documentation at Functions and Operators.
| Function | Description |
|---|---|
experimental_strftime |
Format time using standard strftime notation. |
experimental_strptime |
Format time using standard strptime notation. |
experimental_uuid_v4() |
Return a UUID. |
Vectorized execution on memory-intensive operations
Vectorized query execution in CockroachDB is experimental for the following memory-intensive operations:
- Global sorts
- Window functions
- Unordered aggregations
- Hash joins
- Merge joins on non-unique columns. Merge joins on columns that are guaranteed to have one row per value, also known as "key columns", can execute entirely in-memory.
During the execution of these operations, some intermediate results are written to an in-memory data buffer. In CockroachDB v19.2, the vectorized engine does not spill the contents of intermediate data buffers to disk. As a result, memory-intensive queries can buffer an unlimited quantity of data in memory and lead to memory issues.
To turn vectorized execution on for all operations, set the vectorize session variable to experimental_on.
See Also
SHOW(session)- Functions and Operators
ALTER TABLE ... EXPERIMENTAL_AUDITSHOW TRACE FOR SESSIONSHOW RANGE ... FOR ROW- Vectorized Query Execution
Was this helpful?
