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Merged
iffyio merged 4 commits into from
Feb 3, 2026
Merged

MSSQL: Support standalone BEGIN...END blocks #2186

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b6f225d
MSSQL: Support standalone BEGIN...END blocks
guan404ming Jan 30, 2026
bf35213
Fix lint error
guan404ming Jan 30, 2026
74ce546
Refactor logic to mod.rs
guan404ming Feb 2, 2026
b89d16c
Apply suggestions from code review
guan404ming Feb 3, 2026
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17 changes: 16 additions & 1 deletion src/dialect/mssql.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -145,7 +145,22 @@ impl Dialect for MsSqlDialect {
}

fn parse_statement(&self, parser: &mut Parser) -> Option<Result<Statement, ParserError>> {
if parser.peek_keyword(Keyword::IF) {
if parser.parse_keyword(Keyword::BEGIN) {
if parser.peek_keyword(Keyword::TRANSACTION)
|| parser.peek_keyword(Keyword::WORK)
|| parser.peek_keyword(Keyword::TRY)
|| parser.peek_keyword(Keyword::CATCH)
|| parser.peek_keyword(Keyword::DEFERRED)
|| parser.peek_keyword(Keyword::IMMEDIATE)
|| parser.peek_keyword(Keyword::EXCLUSIVE)
|| parser.peek_token_ref().token == Token::SemiColon
|| parser.peek_token_ref().token == Token::EOF
{
parser.prev_token();
return None;
}
Some(parser.parse_begin_exception_end())
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@iffyio iffyio Jan 31, 2026

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would a condition like this do what we want?

if parse.peek_keywords(BEGIN, TRANSACTION) {
    None
} else if parse_keyword(BEGIN) {
    Some(parser.parse_begin_exception_end())
}

its not super clear to me why the current logic looks at WORK, TRY etc keywords?

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@guan404ming guan404ming Jan 31, 2026 •
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Thanks for the review. These keywords are checked because parse_begin() handles more than just BEGIN TRANSACTION. It also handles WORK, TRY, CATCH, DEFERRED, IMMEDIATE, EXCLUSIVE (since MsSql's supports_start_transaction_modifier() returns true), as well as bare BEGIN;. If any of these are missed, they'd be incorrectly routed to parse_begin_exception_end() and fail to parse.

For example, BEGIN TRY ... END TRY is valid MSSQL syntax. If we only check for BEGIN TRANSACTION, then BEGIN TRY would fall through to parse_begin_exception_end(), which would try to parse TRY as a SQL statement and fail. because TRY is supposed to be handled as a

datafusion-sqlparser-rs/src/parser/mod.rs

Lines 17938 to 17939 in c8b7f7c

} else if self.parse_keyword(Keyword::TRY) {
Some(TransactionModifier::Try)

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@guan404ming guan404ming Jan 31, 2026

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Feel free to let me know if there are any not clear, thanks!

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@iffyio iffyio Feb 2, 2026

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Oh I see, that makes sense! Can we do something like this to clarify the code?

we pull out the linked fallback logic into a function parse_transaction_modifier(). So that it can be reused.

Then here we can do e.g.

if without_modifier = self.maybe_parse(|parser| {
    if parser.parse_transaction_modifier()?.is_some() {
        parser_error!()
    } else {
        Some(())
    }
})?.is_some();

such that with that bool we know whether to defer to the main parser logic or continue with the begin/exception logic

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@guan404ming guan404ming Feb 2, 2026

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Thanks for the really nice suggestion. I just updated it does more clean and work as well.

} else if parser.peek_keyword(Keyword::IF) {
Some(self.parse_if_stmt(parser))
} else if parser.parse_keywords(&[Keyword::CREATE, Keyword::TRIGGER]) {
Some(self.parse_create_trigger(parser, false))
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71 changes: 71 additions & 0 deletions tests/sqlparser_mssql.rs
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Expand Up @@ -2554,3 +2554,74 @@ fn test_sql_keywords_as_column_aliases() {
}
}
}

#[test]
fn parse_mssql_begin_end_block() {
// Single statement
let sql = "BEGIN SELECT 1; END";
let stmt = ms().verified_stmt(sql);
match &stmt {
Statement::StartTransaction {
begin,
has_end_keyword,
statements,
transaction,
modifier,
..
} => {
assert!(begin);
assert!(has_end_keyword);
assert!(transaction.is_none());
assert!(modifier.is_none());
assert_eq!(statements.len(), 1);
}
_ => panic!("Expected StartTransaction, got: {stmt:?}"),
}

// Multiple statements
let sql = "BEGIN SELECT 1; SELECT 2; END";
let stmt = ms().verified_stmt(sql);
match &stmt {
Statement::StartTransaction {
statements,
has_end_keyword,
..
} => {
assert!(has_end_keyword);
assert_eq!(statements.len(), 2);
}
_ => panic!("Expected StartTransaction, got: {stmt:?}"),
}

// DML inside BEGIN/END
let sql = "BEGIN INSERT INTO t VALUES (1); UPDATE t SET x = 2; END";
let stmt = ms().verified_stmt(sql);
match &stmt {
Statement::StartTransaction {
statements,
has_end_keyword,
..
} => {
assert!(has_end_keyword);
assert_eq!(statements.len(), 2);
}
_ => panic!("Expected StartTransaction, got: {stmt:?}"),
}

// BEGIN TRANSACTION still works
let sql = "BEGIN TRANSACTION";
let stmt = ms().verified_stmt(sql);
match &stmt {
Statement::StartTransaction {
begin,
has_end_keyword,
transaction,
..
} => {
assert!(begin);
assert!(!has_end_keyword);
assert!(transaction.is_some());
}
_ => panic!("Expected StartTransaction, got: {stmt:?}"),
}
}