Revert "Add support for Snowflake AT/BEFORE (apache#1667)"

This reverts commit 748a274.

Author: Vedin

src/ast/query.rs

@@ -1873,19 +1873,13 @@ impl fmt::Display for TableAliasColumnDef {
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub enum TableVersion {
-    /// When the table version is defined using `FOR SYSTEM_TIME AS OF`.
-    /// For example: `SELECT * FROM tbl FOR SYSTEM_TIME AS OF TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 1 HOUR)`
     ForSystemTimeAsOf(Expr),
-    /// When the table version is defined using a function.
-    /// For example: `SELECT * FROM tbl AT(TIMESTAMP => '2020-08-14 09:30:00')`
-    Function(Expr),
 }
 
 impl Display for TableVersion {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
             TableVersion::ForSystemTimeAsOf(e) => write!(f, " FOR SYSTEM_TIME AS OF {e}")?,
-            TableVersion::Function(func) => write!(f, " {func}")?,
         }
         Ok(())
     }

src/dialect/bigquery.rs

@@ -77,9 +77,4 @@ impl Dialect for BigQueryDialect {
     fn supports_struct_literal(&self) -> bool {
         true
     }
-
-    // See <https://cloud.google.com/bigquery/docs/access-historical-data>
-    fn supports_timestamp_versioning(&self) -> bool {
-        true
-    }
 }

src/dialect/mod.rs

@@ -834,12 +834,6 @@ pub trait Dialect: Debug + Any {
     fn is_table_factor_alias(&self, explicit: bool, kw: &Keyword, _parser: &mut Parser) -> bool {
         explicit || !keywords::RESERVED_FOR_TABLE_ALIAS.contains(kw)
     }
-
-    /// Returns true if this dialect supports querying historical table data
-    /// by specifying which version of the data to query.
-    fn supports_timestamp_versioning(&self) -> bool {
-        false
-    }
 }
 
 /// This represents the operators for which precedence must be defined

src/dialect/mssql.rs

@@ -90,9 +90,4 @@ impl Dialect for MsSqlDialect {
     fn supports_set_stmt_without_operator(&self) -> bool {
         true
     }
-
-    /// See: <https://learn.microsoft.com/en-us/sql/relational-databases/tables/querying-data-in-a-system-versioned-temporal-table>
-    fn supports_timestamp_versioning(&self) -> bool {
-        true
-    }
 }

src/dialect/snowflake.rs

@@ -307,11 +307,6 @@ impl Dialect for SnowflakeDialect {
             _ => true,
         }
     }
-
-    /// See: <https://docs.snowflake.com/en/sql-reference/constructs/at-before>
-    fn supports_timestamp_versioning(&self) -> bool {
-        true
-    }
 }
 
 fn parse_file_staging_command(kw: Keyword, parser: &mut Parser) -> Result<Statement, ParserError> {

src/parser/mod.rs

@@ -11208,7 +11208,7 @@ impl<'a> Parser<'a> {
             };
 
             // Parse potential version qualifier
-            let version = self.maybe_parse_table_version()?;
+            let version = self.parse_table_version()?;
 
             // Postgres, MSSQL, ClickHouse: table-valued functions:
             let args = if self.consume_token(&Token::LParen) {
@@ -11639,20 +11639,18 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parses a the timestamp version specifier (i.e. query historical data)
-    pub fn maybe_parse_table_version(&mut self) -> Result<Option<TableVersion>, ParserError> {
-        if self.dialect.supports_timestamp_versioning() {
-            if self.parse_keywords(&[Keyword::FOR, Keyword::SYSTEM_TIME, Keyword::AS, Keyword::OF])
-            {
-                let expr = self.parse_expr()?;
-                return Ok(Some(TableVersion::ForSystemTimeAsOf(expr)));
-            } else if self.peek_keyword(Keyword::AT) || self.peek_keyword(Keyword::BEFORE) {
-                let func_name = self.parse_object_name(true)?;
-                let func = self.parse_function(func_name)?;
-                return Ok(Some(TableVersion::Function(func)));
-            }
+    /// Parse a given table version specifier.
+    ///
+    /// For now it only supports timestamp versioning for BigQuery and MSSQL dialects.
+    pub fn parse_table_version(&mut self) -> Result<Option<TableVersion>, ParserError> {
+        if dialect_of!(self is BigQueryDialect | MsSqlDialect)
+            && self.parse_keywords(&[Keyword::FOR, Keyword::SYSTEM_TIME, Keyword::AS, Keyword::OF])
+        {
+            let expr = self.parse_expr()?;
+            Ok(Some(TableVersion::ForSystemTimeAsOf(expr)))
+        } else {
+            Ok(None)
         }
-        Ok(None)
     }
 
     /// Parses MySQL's JSON_TABLE column definition.

tests/sqlparser_snowflake.rs

@@ -3144,10 +3144,3 @@ fn test_sql_keywords_as_select_item_aliases() {
             .is_err());
     }
 }
-
-#[test]
-fn test_timetravel_at_before() {
-    snowflake().verified_only_select("SELECT * FROM tbl AT(TIMESTAMP => '2024-12-15 00:00:00')");
-    snowflake()
-        .verified_only_select("SELECT * FROM tbl BEFORE(TIMESTAMP => '2024-12-15 00:00:00')");
-}