Grammar: Add RESET statement to Postgres dialect (#2182)

Co-authored-by: Barry Pollard <barry@tunetheweb.com>

src/sqlfluff/dialects/dialect_postgres.py

@@ -2764,6 +2764,7 @@ class StatementSegment(BaseSegment):
             Ref("DropDatabaseStatementSegment"),
             Ref("AlterFunctionStatementSegment"),
             Ref("AlterViewStatementSegment"),
+            Ref("ResetStatementSegment"),
             Ref("DiscardStatementSegment"),
         ],
     )
@@ -3057,6 +3058,20 @@ class DropPolicyStatementSegment(BaseSegment):
     )
 
 
+@postgres_dialect.segment()
+class ResetStatementSegment(BaseSegment):
+    """A `RESET` statement.
+
+    As Specified in https://www.postgresql.org/docs/14/sql-reset.html
+    """
+
+    type = "reset_statement"
+    match_grammar = Sequence(
+        "RESET",
+        OneOf("ALL", Ref("ParameterNameSegment")),
+    )
+
+
 @postgres_dialect.segment()
 class DiscardStatementSegment(BaseSegment):
     """A `DISCARD` statement.

test/fixtures/dialects/postgres/postgres_reset.sql

@@ -0,0 +1,2 @@
+RESET timezone;
+RESET ALL;

test/fixtures/dialects/postgres/postgres_reset.yml

@@ -0,0 +1,17 @@
+# YML test files are auto-generated from SQL files and should not be edited by
+# hand. To help enforce this, the "hash" field in the file must match a hash
+# computed by SQLFluff when running the tests. Please run
+# `python test/generate_parse_fixture_yml.py`  to generate them after adding or
+# altering SQL files.
+_hash: e9e279911916c47d20deb5cce0ef040ce5e573f71b5044dc43b3a1f3b64bbc23
+file:
+- statement:
+    reset_statement:
+      keyword: RESET
+      parameter: timezone
+- statement_terminator: ;
+- statement:
+    reset_statement:
+    - keyword: RESET
+    - keyword: ALL
+- statement_terminator: ;