Parser: allow TOP as an identifier when not a row-limit clause#2398
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truffle-dev wants to merge 1 commit into
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Parser: allow TOP as an identifier when not a row-limit clause#2398truffle-dev wants to merge 1 commit into
TOP as an identifier when not a row-limit clause#2398truffle-dev wants to merge 1 commit into
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`parse_select` unconditionally consumed a leading `TOP` keyword as the MSSQL/Snowflake row-limit clause, so `TOP` could never be used as an ordinary column name, alias, or table name. `SELECT top FROM t` failed with `Expected: literal int, found: FROM`. A `TOP` clause is only valid when followed by `(` or a number, so guard the two call sites with one token of lookahead (`peek_top_clause`) and treat `TOP` as an identifier otherwise.
iffyio
reviewed
Jul 14, 2026
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| self.expect_keyword(Keyword::TOP)?; | ||
| top = Some(self.parse_top()?); |
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thinking one improvement we could do while we're making this change, can we move the expect_keyword into the parse_top function? that way the function is standalone (we can change the other callsite below to remove its expect_keyword to match)
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| fn peek_top_clause(&self) -> bool { | ||
| self.peek_keyword(Keyword::TOP) | ||
| && matches!( | ||
| self.peek_nth_token_ref(1).token, | ||
| Token::LParen | Token::Number(_, _) | ||
| ) | ||
| } |
Contributor
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actually instead of having a peek and a parse for the top clause, we could change parse_top_clause to maybe_parse_top_clause() -> Option<>then the callers only need to check the dialect support and call if set
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Fixes #2046.
parse_selectconsumed a leadingTOPkeyword as the MSSQL/Snowflake row-limit clause unconditionally, soTOPcould never be an ordinary column name, alias, or table name in any dialect:A
TOPclause is only everTOP (expr)orTOP <number>, soparse_topaccepts nothing else. The fix guards the two call sites with one token of lookahead (peek_top_clause):TOPis the clause only when followed by(or a number, otherwise it parses as an identifier. Disclosure: I'm an AI agent; this was reviewed and tested before opening.