Added alter external table support for snowflake (#2122)

Author: romanoff

src/ast/ddl.rs

@@ -371,10 +371,15 @@ pub enum AlterTableOperation {
     DropClusteringKey,
     SuspendRecluster,
     ResumeRecluster,
-    /// `REFRESH`
+    /// `REFRESH [ '<subpath>' ]`
     ///
-    /// Note: this is Snowflake specific for dynamic tables <https://docs.snowflake.com/en/sql-reference/sql/alter-table>
-    Refresh,
+    /// Note: this is Snowflake specific for dynamic/external tables
+    /// <https://docs.snowflake.com/en/sql-reference/sql/alter-dynamic-table>
+    /// <https://docs.snowflake.com/en/sql-reference/sql/alter-external-table>
+    Refresh {
+        /// Optional subpath for external table refresh
+        subpath: Option<String>,
+    },
     /// `SUSPEND`
     ///
     /// Note: this is Snowflake specific for dynamic tables <https://docs.snowflake.com/en/sql-reference/sql/alter-table>
@@ -863,8 +868,12 @@ impl fmt::Display for AlterTableOperation {
                 write!(f, "RESUME RECLUSTER")?;
                 Ok(())
             }
-            AlterTableOperation::Refresh => {
-                write!(f, "REFRESH")
+            AlterTableOperation::Refresh { subpath } => {
+                write!(f, "REFRESH")?;
+                if let Some(path) = subpath {
+                    write!(f, " '{path}'")?;
+                }
+                Ok(())
             }
             AlterTableOperation::Suspend => {
                 write!(f, "SUSPEND")
@@ -3977,8 +3986,11 @@ pub enum AlterTableType {
     /// <https://docs.snowflake.com/en/sql-reference/sql/alter-iceberg-table>
     Iceberg,
     /// Dynamic table type
-    /// <https://docs.snowflake.com/en/sql-reference/sql/alter-table>
+    /// <https://docs.snowflake.com/en/sql-reference/sql/alter-dynamic-table>
     Dynamic,
+    /// External table type
+    /// <https://docs.snowflake.com/en/sql-reference/sql/alter-external-table>
+    External,
 }
 
 /// ALTER TABLE statement
@@ -4008,6 +4020,7 @@ impl fmt::Display for AlterTable {
         match &self.table_type {
             Some(AlterTableType::Iceberg) => write!(f, "ALTER ICEBERG TABLE ")?,
             Some(AlterTableType::Dynamic) => write!(f, "ALTER DYNAMIC TABLE ")?,
+            Some(AlterTableType::External) => write!(f, "ALTER EXTERNAL TABLE ")?,
             None => write!(f, "ALTER TABLE ")?,
         }
 

src/ast/spans.rs

@@ -1145,7 +1145,7 @@ impl Spanned for AlterTableOperation {
             AlterTableOperation::DropClusteringKey => Span::empty(),
             AlterTableOperation::SuspendRecluster => Span::empty(),
             AlterTableOperation::ResumeRecluster => Span::empty(),
-            AlterTableOperation::Refresh => Span::empty(),
+            AlterTableOperation::Refresh { .. } => Span::empty(),
             AlterTableOperation::Suspend => Span::empty(),
             AlterTableOperation::Resume => Span::empty(),
             AlterTableOperation::Algorithm { .. } => Span::empty(),

src/dialect/snowflake.rs

@@ -221,6 +221,11 @@ impl Dialect for SnowflakeDialect {
             return Some(parse_alter_dynamic_table(parser));
         }
 
+        if parser.parse_keywords(&[Keyword::ALTER, Keyword::EXTERNAL, Keyword::TABLE]) {
+            // ALTER EXTERNAL TABLE
+            return Some(parse_alter_external_table(parser));
+        }
+
         if parser.parse_keywords(&[Keyword::ALTER, Keyword::SESSION]) {
             // ALTER SESSION
             let set = match parser.parse_one_of_keywords(&[Keyword::SET, Keyword::UNSET]) {
@@ -619,7 +624,7 @@ fn parse_alter_dynamic_table(parser: &mut Parser) -> Result<Statement, ParserErr
 
     // Parse the operation (REFRESH, SUSPEND, or RESUME)
     let operation = if parser.parse_keyword(Keyword::REFRESH) {
-        AlterTableOperation::Refresh
+        AlterTableOperation::Refresh { subpath: None }
     } else if parser.parse_keyword(Keyword::SUSPEND) {
         AlterTableOperation::Suspend
     } else if parser.parse_keyword(Keyword::RESUME) {
@@ -649,6 +654,45 @@ fn parse_alter_dynamic_table(parser: &mut Parser) -> Result<Statement, ParserErr
     }))
 }
 
+/// Parse snowflake alter external table.
+/// <https://docs.snowflake.com/en/sql-reference/sql/alter-external-table>
+fn parse_alter_external_table(parser: &mut Parser) -> Result<Statement, ParserError> {
+    let if_exists = parser.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);
+    let table_name = parser.parse_object_name(true)?;
+
+    // Parse the operation (REFRESH for now)
+    let operation = if parser.parse_keyword(Keyword::REFRESH) {
+        // Optional subpath for refreshing specific partitions
+        let subpath = match parser.peek_token().token {
+            Token::SingleQuotedString(s) => {
+                parser.next_token();
+                Some(s)
+            }
+            _ => None,
+        };
+        AlterTableOperation::Refresh { subpath }
+    } else {
+        return parser.expected("REFRESH after ALTER EXTERNAL TABLE", parser.peek_token());
+    };
+
+    let end_token = if parser.peek_token_ref().token == Token::SemiColon {
+        parser.peek_token_ref().clone()
+    } else {
+        parser.get_current_token().clone()
+    };
+
+    Ok(Statement::AlterTable(AlterTable {
+        name: table_name,
+        if_exists,
+        only: false,
+        operations: vec![operation],
+        location: None,
+        on_cluster: None,
+        table_type: Some(AlterTableType::External),
+        end_token: AttachedToken(end_token),
+    }))
+}
+
 /// Parse snowflake alter session.
 /// <https://docs.snowflake.com/en/sql-reference/sql/alter-session>
 fn parse_alter_session(parser: &mut Parser, set: bool) -> Result<Statement, ParserError> {

tests/sqlparser_snowflake.rs

@@ -4635,3 +4635,12 @@ fn test_alter_dynamic_table() {
     snowflake().verified_stmt("ALTER DYNAMIC TABLE my_dyn_table SUSPEND");
     snowflake().verified_stmt("ALTER DYNAMIC TABLE my_dyn_table RESUME");
 }
+
+#[test]
+fn test_alter_external_table() {
+    snowflake().verified_stmt("ALTER EXTERNAL TABLE some_table REFRESH");
+    snowflake().verified_stmt("ALTER EXTERNAL TABLE some_table REFRESH 'year=2025/month=12/'");
+    snowflake().verified_stmt("ALTER EXTERNAL TABLE IF EXISTS some_table REFRESH");
+    snowflake()
+        .verified_stmt("ALTER EXTERNAL TABLE IF EXISTS some_table REFRESH 'year=2025/month=12/'");
+}