Simplify dialect settings wrt to insert alias

Author: xitep

src/dialect/mod.rs

@@ -1240,14 +1240,8 @@ pub trait Dialect: Debug + Any {
         false
     }
 
-    /// Returns true if this dialect supports `INSERT INTO t AS alias ...`.
-    fn supports_insert_table_explicit_alias(&self) -> bool {
-        false
-    }
-
-    /// Returns true if this dialect supports `INSERT INTO t alias ...` with
-    /// `alias` _not_ preceded by the "AS" keyword.
-    fn supports_insert_table_implicit_alias(&self) -> bool {
+    /// Returns true if this dialect supports `INSERT INTO t [[AS] alias] ...`.
+    fn supports_insert_table_alias(&self) -> bool {
         false
     }
 

src/dialect/oracle.rs

@@ -111,10 +111,7 @@ impl Dialect for OracleDialect {
         true
     }
 
-    /// Supports insert table aliases (but with no preceding "AS" keyword)
-    ///
-    /// See <https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/INSERT.html#GUID-903F8043-0254-4EE9-ACC1-CB8AC0AF3423__GUID-AC239E95-0DD5-4F4B-A849-55C87840D0E6>
-    fn supports_insert_table_implicit_alias(&self) -> bool {
+    fn supports_insert_table_alias(&self) -> bool {
         true
     }
 }

src/dialect/postgresql.rs

@@ -289,10 +289,7 @@ impl Dialect for PostgreSqlDialect {
         true
     }
 
-    /// [Postgres] supports insert table aliases with an explicit "AS" keyword.
-    ///
-    /// [Postgres]: https://www.postgresql.org/docs/17/sql-insert.html
-    fn supports_insert_table_explicit_alias(&self) -> bool {
+    fn supports_insert_table_alias(&self) -> bool {
         true
     }
 }

src/parser/mod.rs

@@ -17229,24 +17229,24 @@ impl<'a> Parser<'a> {
             let table = self.parse_keyword(Keyword::TABLE);
             let table_object = self.parse_table_object()?;
 
-            let table_alias = if self.dialect.supports_insert_table_implicit_alias()
+            let table_alias = if self.dialect.supports_insert_table_alias()
                 && !self.peek_sub_query()
                 && self
-                    .peek_one_of_keywords(&[Keyword::AS, Keyword::DEFAULT, Keyword::VALUES])
+                    .peek_one_of_keywords(&[Keyword::DEFAULT, Keyword::VALUES])
                     .is_none()
             {
-                self.maybe_parse(|parser| parser.parse_identifier())?
-                    .map(|alias| TableAliasWithoutColumns {
-                        explicit: false,
-                        alias,
+                if self.parse_keyword(Keyword::AS) {
+                    Some(TableAliasWithoutColumns {
+                        explicit: true,
+                        alias: self.parse_identifier()?,
                     })
-            } else if self.dialect.supports_insert_table_explicit_alias()
-                && self.parse_keyword(Keyword::AS)
-            {
-                Some(TableAliasWithoutColumns {
-                    explicit: true,
-                    alias: self.parse_identifier()?,
-                })
+                } else {
+                    self.maybe_parse(|parser| parser.parse_identifier())?
+                        .map(|alias| TableAliasWithoutColumns {
+                            explicit: false,
+                            alias,
+                        })
+                }
             } else {
                 None
             };

tests/sqlparser_oracle.rs

@@ -490,15 +490,6 @@ fn test_insert_without_alias() {
         ))
     );
 
-    // check AS
-    let sql = "INSERT INTO AS t default SELECT 'a' FROM dual";
-    assert_eq!(
-        oracle_dialect.parse_sql_statements(sql),
-        Err(ParserError::ParserError(
-            "Expected: SELECT, VALUES, or a subquery in the query body, found: default".into()
-        ))
-    );
-
     // check SELECT
     let sql = "INSERT INTO t SELECT 'a' FROM dual";
     let stmt = oracle_dialect.verified_stmt(sql);