Grammar: Add complete datetime units to postgres dialect (#2025)

src/sqlfluff/dialects/dialect_postgres.py

@@ -134,8 +134,24 @@
     get_keywords(postgres_keywords, "not-keyword")
 )
 
-# Add the EPOCH datetime unit
-postgres_dialect.sets("datetime_units").update(["EPOCH"])
+# Add datetime units
+postgres_dialect.sets("datetime_units").update(
+    [
+        "CENTURY",
+        "DECADE",
+        "DOW",
+        "DOY",
+        "EPOCH",
+        "ISODOW",
+        "ISOYEAR",
+        "MICROSECONDS",
+        "MILLENNIUM",
+        "MILLISECONDS",
+        "TIMEZONE",
+        "TIMEZONE_HOUR",
+        "TIMEZONE_MINUTE",
+    ]
+)
 
 postgres_dialect.add(
     JsonOperatorSegment=NamedParser(

test/fixtures/dialects/postgres/postgres_datetime_units.sql

@@ -0,0 +1,64 @@
+SELECT
+    t1.field,
+    EXTRACT(CENTURY FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(DECADE FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(DOW FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(DOY FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(EPOCH FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(ISODOW FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(ISOYEAR FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(MICROSECONDS FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(MILLENNIUM FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(MILLISECONDS FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(TIMEZONE FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(TIMEZONE_HOUR FROM t1.sometime) AS a
+FROM t1;
+
+SELECT
+    t1.field,
+    EXTRACT(TIMEZONE_MINUTE FROM t1.sometime) AS a
+FROM t1;