ref-docs: sql: add remaining compatibility fixes for pg_dump

src/current/v26.1/lock.md

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+---
+title: sql: add remaining compatibility fixes for pg_dump
+summary: ```yaml
+toc: true
+docs_area: reference
+---
+
+```yaml
+---
+title: LOCK
+summary: Acquire table-level locks for PostgreSQL compatibility.
+toc: true
+docs_area: reference.sql
+---
+```
+
+The `LOCK` statement acquires table-level locks on specified tables. This statement is primarily intended for PostgreSQL compatibility, particularly with `pg_dump`. When the `pg_dump_compatibility` cluster setting is enabled, all lock modes are accepted as no-ops since CockroachDB uses Multi-Version Concurrency Control (MVCC) where reads never block. When compatibility mode is disabled, `LOCK` returns a feature not supported error.
+
+## Required privileges
+
+No specific privileges are documented in the implementation. [NEEDS REVIEW: privilege requirements]
+
+## Synopsis
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+LOCK [TABLE] table_name [, ...] [IN lock_mode MODE] [NOWAIT]
+~~~
+
+## Parameters
+
+| Parameter | Description | Required |
+|-----------|-------------|----------|
+| `table_name` | The name of the table(s) to lock. Multiple tables can be specified as a comma-separated list. | Yes |
+| `lock_mode` | The lock mode to acquire. If omitted, defaults to `ACCESS EXCLUSIVE`. | No |
+| `NOWAIT` | If specified, the statement will not wait if the lock cannot be acquired immediately. In CockroachDB, this has no effect when `pg_dump_compatibility` is enabled. | No |
+
+### Lock modes
+
+The following lock modes are supported:
+
+- `ACCESS SHARE`
+- `ROW SHARE`  
+- `ROW EXCLUSIVE`
+- `SHARE UPDATE EXCLUSIVE`
+- `SHARE ROW EXCLUSIVE`
+- `SHARE`
+- `EXCLUSIVE`
+- `ACCESS EXCLUSIVE` (default when no mode specified)
+
+{{site.data.alerts.callout_info}}
+All lock modes are treated as no-ops when `pg_dump_compatibility` is enabled, since CockroachDB's MVCC concurrency control makes explicit locking unnecessary.
+{{site.data.alerts.end}}
+
+## Examples
+
+### Basic table locking
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+SET pg_dump_compatibility = 'postgres';
+LOCK TABLE employees IN ACCESS SHARE MODE;
+~~~
+
+### Locking multiple tables
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+LOCK TABLE employees, departments IN ACCESS SHARE MODE;
+~~~
+
+### Using NOWAIT
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+LOCK TABLE employees IN ACCESS SHARE MODE NOWAIT;
+~~~
+
+### Default lock mode (ACCESS EXCLUSIVE)
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+LOCK TABLE employees;
+~~~
+
+### Without TABLE keyword
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+LOCK employees IN SHARE MODE;
+~~~
+
+## Compatibility notes
+
+{{site.data.alerts.callout_danger}}
+`LOCK TABLE` is only supported when the `pg_dump_compatibility` cluster setting is enabled. When disabled, all `LOCK` statements return a "feature not supported" error.
+{{site.data.alerts.end}}
+
+{% include_cached copy-clipboard.html %}
+~~~ sql
+-- Enable pg_dump compatibility
+SET pg_dump_compatibility = 'postgres';
+
+-- Now LOCK statements work
+LOCK TABLE mytable IN ACCESS SHARE MODE;
+
+-- Disable compatibility  
+SET pg_dump_compatibility = 'off';
+
+-- This will now fail
+LOCK TABLE mytable IN ACCESS SHARE MODE;
+-- Error: LOCK TABLE is not supported
+~~~
+
+## See also
+
+- [`SET (session variable)`]({% link {{ page.version.version }}/set-vars.md %}) for setting `pg_dump_compatibility`
+- [PostgreSQL compatibility]({% link {{ page.version.version }}/postgresql-compatibility.md %})