Grammar: Fix TRUNCATE statement in Postgres dialect

src/sqlfluff/dialects/dialect_postgres.py

@@ -3105,3 +3105,39 @@ class DiscardStatementSegment(BaseSegment):
             "TEMP",
         ),
     )
+
+
+@postgres_dialect.segment(replace=True)
+class TruncateStatementSegment(BaseSegment):
+    """`TRUNCATE TABLE` statement.
+
+    https://www.postgresql.org/docs/14/sql-truncate.html
+    """
+
+    type = "truncate_table"
+    match_grammar = Sequence(
+        "TRUNCATE",
+        Ref.keyword("TABLE", optional=True),
+        Delimited(
+            OneOf(
+                Sequence(
+                    Ref.keyword("ONLY", optional=True),
+                    Ref("TableReferenceSegment"),
+                ),
+                Sequence(
+                    Ref("TableReferenceSegment"),
+                    Ref("StarSegment", optional=True),
+                ),
+            ),
+        ),
+        Sequence(
+            OneOf("RESTART", "CONTINUE"),
+            "IDENTITY",
+            optional=True,
+        ),
+        OneOf(
+            "CASCADE",
+            "RESTRICT",
+            optional=True,
+        ),
+    )

test/fixtures/dialects/postgres/postgres_truncate.sql

@@ -0,0 +1,20 @@
+TRUNCATE bigtable;
+TRUNCATE some_schema.bigtable;
+TRUNCATE TABLE bigtable;
+TRUNCATE ONLY bigtable;
+TRUNCATE TABLE ONLY bigtable;
+TRUNCATE bigtable *;
+TRUNCATE TABLE bigtable *;
+TRUNCATE bigtable, fattable;
+TRUNCATE TABLE bigtable, fattable;
+TRUNCATE ONLY bigtable, fattable *;
+TRUNCATE bigtable RESTART IDENTITY;
+TRUNCATE bigtable CONTINUE IDENTITY;
+TRUNCATE bigtable CASCADE;
+TRUNCATE bigtable RESTRICT;
+TRUNCATE TABLE
+    ONLY bigtable,
+    fattable *,
+    ONLY slimtable
+CONTINUE IDENTITY CASCADE;
+

test/fixtures/dialects/postgres/postgres_truncate.yml

@@ -0,0 +1,137 @@
+# 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: b48839242732786fa04eb942fffb75a3fc7f0e195dd2da275337d7fe481be2d8
+file:
+- statement:
+    truncate_table:
+      keyword: TRUNCATE
+      table_reference:
+        identifier: bigtable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+      keyword: TRUNCATE
+      table_reference:
+      - identifier: some_schema
+      - dot: .
+      - identifier: bigtable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: TABLE
+    - table_reference:
+        identifier: bigtable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: ONLY
+    - table_reference:
+        identifier: bigtable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: TABLE
+    - keyword: ONLY
+    - table_reference:
+        identifier: bigtable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+      keyword: TRUNCATE
+      table_reference:
+        identifier: bigtable
+      star: '*'
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: TABLE
+    - table_reference:
+        identifier: bigtable
+    - star: '*'
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - table_reference:
+        identifier: bigtable
+    - comma: ','
+    - table_reference:
+        identifier: fattable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: TABLE
+    - table_reference:
+        identifier: bigtable
+    - comma: ','
+    - table_reference:
+        identifier: fattable
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: ONLY
+    - table_reference:
+        identifier: bigtable
+    - comma: ','
+    - table_reference:
+        identifier: fattable
+    - star: '*'
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - table_reference:
+        identifier: bigtable
+    - keyword: RESTART
+    - keyword: IDENTITY
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - table_reference:
+        identifier: bigtable
+    - keyword: CONTINUE
+    - keyword: IDENTITY
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - table_reference:
+        identifier: bigtable
+    - keyword: CASCADE
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - table_reference:
+        identifier: bigtable
+    - keyword: RESTRICT
+- statement_terminator: ;
+- statement:
+    truncate_table:
+    - keyword: TRUNCATE
+    - keyword: TABLE
+    - keyword: ONLY
+    - table_reference:
+        identifier: bigtable
+    - comma: ','
+    - table_reference:
+        identifier: fattable
+    - star: '*'
+    - comma: ','
+    - keyword: ONLY
+    - table_reference:
+        identifier: slimtable
+    - keyword: CONTINUE
+    - keyword: IDENTITY
+    - keyword: CASCADE
+- statement_terminator: ;