Merge cockroachdb#128540

128540: sql: support creating and dropping triggers r=DrewKimball a=DrewKimball

#### sql: add trigger descriptor

This commit adds a `Triggers` field to the table descriptor, which is
a list of `TriggerDescriptor` structs. `TriggerDescriptor` contains all
the information needed to build and execute a trigger, including the
timing, matched event type, and fully-resolved trigger function body.
This commit also adds the logic needed to track and update object
references and back-references within descriptors due to triggers.

Informs cockroachdb#126359

Release note: None

#### schemachanger: support CREATE TRIGGER in the declarative schema changer

This commit adds support for `CREATE TRIGGER` statements to the declarative
schema changer. The implementation assumes that most of the validation will
be carried out during planning, apart from checking for cross-database
references. Note that `CREATE TRIGGER` will not be implemented in the
legacy schema changer.

Informs cockroachdb#126359

Release note: None

#### schemachanger: support DROP TRIGGER in the declarative schema changer

This commit adds `DROP TRIGGER` support to the declarative schema changer.
Just as with `CREATE TRIGGER`, `DROP TRIGGER` will not be implemented in
the legacy schema changer.

Informs cockroachdb#126359

Release note (sql change): Implemented DROP TRIGGER statements. Note that
the CASCADE option for dropping a trigger is not supported.

#### opt: add support for CREATE TRIGGER in optimizer

This commit finalizes support for `CREATE TRIGGER` by adding support
for it in the optimizer. This includes validation for the statement,
dependency resolution, and logic tests.

Fixes cockroachdb#126359

Release note (sql change): Added support for CREATE TRIGGER. Note that
OR REPLACE syntax is not yet supported.

Co-authored-by: Drew Kimball <[email protected]>

docs/generated/eventlog.md

@@ -1380,6 +1380,30 @@ An event of type `create_table` is recorded when a table is created.
 | `Owner` | The name of the owner for the new table. | yes |
 
 
+#### Common fields
+
+| Field | Description | Sensitive |
+|--|--|--|
+| `Timestamp` | The timestamp of the event. Expressed as nanoseconds since the Unix epoch. | no |
+| `EventType` | The type of the event. | no |
+| `Statement` | A normalized copy of the SQL statement that triggered the event. The statement string contains a mix of sensitive and non-sensitive details (it is redactable). | partially |
+| `Tag` | The statement tag. This is separate from the statement string, since the statement string can contain sensitive information. The tag is guaranteed not to. | no |
+| `User` | The user account that triggered the event. The special usernames `root` and `node` are not considered sensitive. | depends |
+| `DescriptorID` | The primary object descriptor affected by the operation. Set to zero for operations that don't affect descriptors. | no |
+| `ApplicationName` | The application name for the session where the event was emitted. This is included in the event to ease filtering of logging output by application. | no |
+| `PlaceholderValues` | The mapping of SQL placeholders to their values, for prepared statements. | yes |
+
+### `create_trigger`
+
+An event of type `create_trigger` is recorded when a trigger is created.
+
+
+| Field | Description | Sensitive |
+|--|--|--|
+| `TableName` | Name of the trigger's table. | yes |
+| `TriggerName` | Name of the created trigger. | yes |
+
+
 #### Common fields
 
 | Field | Description | Sensitive |
@@ -1473,7 +1497,7 @@ An event of type `drop_function` is recorded when a user-defined function is dro
 
 | Field | Description | Sensitive |
 |--|--|--|
-| `FunctionName` | Name of the created function. | yes |
+| `FunctionName` | Name of the dropped function. | yes |
 
 
 #### Common fields
@@ -1572,6 +1596,30 @@ An event of type `drop_table` is recorded when a table is dropped.
 | `CascadeDroppedViews` | The names of the views dropped as a result of a cascade operation. | yes |
 
 
+#### Common fields
+
+| Field | Description | Sensitive |
+|--|--|--|
+| `Timestamp` | The timestamp of the event. Expressed as nanoseconds since the Unix epoch. | no |
+| `EventType` | The type of the event. | no |
+| `Statement` | A normalized copy of the SQL statement that triggered the event. The statement string contains a mix of sensitive and non-sensitive details (it is redactable). | partially |
+| `Tag` | The statement tag. This is separate from the statement string, since the statement string can contain sensitive information. The tag is guaranteed not to. | no |
+| `User` | The user account that triggered the event. The special usernames `root` and `node` are not considered sensitive. | depends |
+| `DescriptorID` | The primary object descriptor affected by the operation. Set to zero for operations that don't affect descriptors. | no |
+| `ApplicationName` | The application name for the session where the event was emitted. This is included in the event to ease filtering of logging output by application. | no |
+| `PlaceholderValues` | The mapping of SQL placeholders to their values, for prepared statements. | yes |
+
+### `drop_trigger`
+
+An event of type `drop_trigger` is recorded when a trigger is dropped.
+
+
+| Field | Description | Sensitive |
+|--|--|--|
+| `TableName` | Name of the trigger's table. | yes |
+| `TriggerName` | Name of the dropped trigger. | yes |
+
+
 #### Common fields
 
 | Field | Description | Sensitive |

docs/generated/sql/bnf/stmt_block.bnf

@@ -3260,7 +3260,6 @@ trigger_event ::=
  | 'UPDATE'
  | 'UPDATE' 'OF' name_list
  | 'TRUNCATE'
- | 'UPSERT'
 
 trigger_transition_list ::=
  ( trigger_transition ) ( ( trigger_transition ) )*