PostgreSQL: Allow non-reserved keywords as table aliases

src/dialect/postgresql.rs

@@ -33,7 +33,21 @@ use crate::keywords::Keyword;
 use crate::parser::{Parser, ParserError};
 use crate::tokenizer::Token;
 
-use super::keywords::RESERVED_FOR_IDENTIFIER;
+use super::keywords::{self, RESERVED_FOR_IDENTIFIER};
+
+/// Keywords in [`keywords::RESERVED_FOR_TABLE_ALIAS`] because of other dialects, yet are safe for aliasing in PostgreSQL.
+/// See <https://www.postgresql.org/docs/current/sql-keywords-appendix.html>.
+const RESERVED_EXCLUSIONS_FOR_TABLE_ALIAS: &[Keyword] = &[
+    Keyword::CLUSTER,
+    Keyword::DISTRIBUTE,
+    Keyword::EXPLAIN,
+    Keyword::MINUS,
+    Keyword::SAMPLE,
+    Keyword::SORT,
+    Keyword::START,
+    Keyword::TOP,
+    Keyword::VIEW,
+];
 
 /// A [`Dialect`] for [PostgreSQL](https://www.postgresql.org/)
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
@@ -91,6 +105,11 @@ impl Dialect for PostgreSqlDialect {
         }
     }
 
+    fn is_table_alias(&self, kw: &Keyword, _parser: &mut Parser) -> bool {
+        !keywords::RESERVED_FOR_TABLE_ALIAS.contains(kw)
+            || RESERVED_EXCLUSIONS_FOR_TABLE_ALIAS.contains(kw)
+    }
+
     /// See <https://www.postgresql.org/docs/current/sql-createoperator.html>
     fn is_custom_operator_part(&self, ch: char) -> bool {
         matches!(

tests/sqlparser_postgres.rs

@@ -9852,3 +9852,26 @@ fn parse_alter_table_constraint_check_no_inherit() {
     }
     pg_and_generic().verified_stmt("ALTER TABLE docs ADD CONSTRAINT c CHECK (id > 0) NO INHERIT");
 }
+
+#[test]
+fn parse_non_reserved_keywords_as_table_alias() {
+    // PostgreSQL allows these keywords as explicit table aliases.
+    for kw in [
+        "cluster",
+        "distribute",
+        "explain",
+        "minus",
+        "sample",
+        "sort",
+        "start",
+        "top",
+        "view",
+    ] {
+        pg().verified_stmt(&format!(
+            "SELECT * FROM tbl_name AS {kw} JOIN tbl_name_2 ON {kw}.id = tbl_name_2.id"
+        ));
+        pg().verified_stmt(&format!(
+            "SELECT * FROM tbl_name {kw} JOIN tbl_name_2 ON {kw}.id = tbl_name_2.id"
+        ));
+    }
+}