Merge cockroachdb#130089

130089: sql: make sql.txn.repeatable_read_isolation.enabled public r=dikshant a=nvanbenschoten

This commit makes the `sql.txn.repeatable_read_isolation.enabled` cluster setting public, as part of moving REPEATABLE READ isolation into a public preview.

Epic: None

Release note (sql change): The cluster setting
`sql.txn.repeatable_read_isolation.enabled` was added and defaults to false. When set to true, the following statements will configure transactions to run under REPEATABLE READ isolation, rather than being automatically interpreted as SERIALIZABLE.
- `BEGIN TRANSACTION ISOLATION LEVEL REPEATABLE READ`
- `SET TRANSACTION ISOLATION LEVEL REPEATABLE READ`
- `SET default_transaction_isolation = 'repeatable read'`
- `SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL REPEATABLE READ`

This setting was added since REPEATABLE READ transactions are a preview feature, so usage of it is opt-in for v24.3. In a future CockroachDB major version, this setting will change to default to true.

Co-authored-by: Nathan VanBenschoten <[email protected]>

docs/generated/settings/settings-for-tenants.txt

@@ -382,6 +382,7 @@ sql.ttl.default_select_batch_size	integer	500	default amount of rows to select i
 sql.ttl.default_select_rate_limit	integer	0	default select rate limit (rows per second) per node for each TTL job. Use 0 to signify no rate limit.	application
 sql.ttl.job.enabled	boolean	true	whether the TTL job is enabled	application
 sql.txn.read_committed_isolation.enabled	boolean	true	set to true to allow transactions to use the READ COMMITTED isolation level if specified by BEGIN/SET commands	application
+sql.txn.repeatable_read_isolation.enabled (alias: sql.txn.snapshot_isolation.enabled)	boolean	false	set to true to allow transactions to use the REPEATABLE READ isolation level if specified by BEGIN/SET commands	application
 sql.txn_fingerprint_id_cache.capacity	integer	100	the maximum number of txn fingerprint IDs stored	application
 storage.ingestion.value_blocks.enabled	boolean	true	set to true to enable writing of value blocks in ingestion sstables	application
 storage.max_sync_duration	duration	20s	maximum duration for disk operations; any operations that take longer than this setting trigger a warning log entry or process crash	system-visible

docs/generated/settings/settings.html

@@ -335,6 +335,7 @@
 <tr><td><div id="setting-sql-ttl-default-select-rate-limit" class="anchored"><code>sql.ttl.default_select_rate_limit</code></div></td><td>integer</td><td><code>0</code></td><td>default select rate limit (rows per second) per node for each TTL job. Use 0 to signify no rate limit.</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-sql-ttl-job-enabled" class="anchored"><code>sql.ttl.job.enabled</code></div></td><td>boolean</td><td><code>true</code></td><td>whether the TTL job is enabled</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-sql-txn-read-committed-isolation-enabled" class="anchored"><code>sql.txn.read_committed_isolation.enabled</code></div></td><td>boolean</td><td><code>true</code></td><td>set to true to allow transactions to use the READ COMMITTED isolation level if specified by BEGIN/SET commands</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
+<tr><td><div id="setting-sql-txn-snapshot-isolation-enabled" class="anchored"><code>sql.txn.repeatable_read_isolation.enabled<br />(alias: sql.txn.snapshot_isolation.enabled)</code></div></td><td>boolean</td><td><code>false</code></td><td>set to true to allow transactions to use the REPEATABLE READ isolation level if specified by BEGIN/SET commands</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-sql-txn-fingerprint-id-cache-capacity" class="anchored"><code>sql.txn_fingerprint_id_cache.capacity</code></div></td><td>integer</td><td><code>100</code></td><td>the maximum number of txn fingerprint IDs stored</td><td>Serverless/Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-storage-experimental-eventually-file-only-snapshots-enabled" class="anchored"><code>storage.experimental.eventually_file_only_snapshots.enabled</code></div></td><td>boolean</td><td><code>true</code></td><td>set to false to disable eventually-file-only-snapshots (kv.snapshot_receiver.excise.enabled must also be false)</td><td>Dedicated/Self-Hosted</td></tr>
 <tr><td><div id="setting-storage-ingest-split-enabled" class="anchored"><code>storage.ingest_split.enabled</code></div></td><td>boolean</td><td><code>true</code></td><td>set to false to disable ingest-time splitting that lowers write-amplification</td><td>Dedicated/Self-Hosted</td></tr>

pkg/sql/conn_executor.go

@@ -3533,10 +3533,10 @@ var allowRepeatableReadIsolation = settings.RegisterBoolSetting(
 	settings.ApplicationLevel,
 	"sql.txn.snapshot_isolation.enabled",
 	"set to true to allow transactions to use the REPEATABLE READ isolation "+
-		"level. At the time of writing, this setting is intended only for usage by "+
-		"CockroachDB developers.",
+		"level if specified by BEGIN/SET commands",
 	false,
 	settings.WithName("sql.txn.repeatable_read_isolation.enabled"),
+	settings.WithPublic,
 )
 
 var logIsolationLevelLimiter = log.Every(10 * time.Second)