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Let postfix IS tests chain onto predicate results - #2840
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manticore-projects merged 1 commit intoOct 21, 2026
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A boolean test applied to a comparison or another predicate was a
parse error: a > 0 IS TRUE, a IN (1, 2) IS FALSE, a IS NULL IS NOT
TRUE all failed at the IS, though SQL:2016 6.39 applies IS [NOT]
{TRUE|FALSE|UNKNOWN} to any boolean primary and PostgreSQL, MySQL
and SQLite accept the forms.
After the first condition suffix, postfix IS predicates (IS [NOT]
NULL / TRUE / FALSE / UNKNOWN / JSON) now chain onto the result. A
semantic guard keeps the loop from claiming IS DISTINCT FROM and
from consuming a column's NOT NULL constraint after a DEFAULT
expression.
Fixes JSQLParser#2759
Contributor
That's a strong argument, even I can't ignore. |
| | LOOKAHEAD(3) result=IsDistinctExpression(left) | ||
| | result=SimilarToExpression(left) | ||
| ) | ||
| // SQL:2016 6.39: a boolean test applies to any boolean primary, |
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Kudos, clean documentation! I like this.
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Summary
A boolean test applied to a comparison or another predicate is a parse error:
a > 0 IS TRUE,a IN (1, 2) IS FALSEanda IS NULL IS NOT TRUEall fail at theIS, while the same tests on a bare column or a parenthesized comparison parse (#2759).SQL:2016 6.39 defines
<boolean test> ::= <boolean primary> [ IS [NOT] <truth value> ], so the test applies to any boolean primary. PostgreSQL, MySQL and SQLite all accept these forms.The condition suffix dispatch fired once:
a > 0consumed the>comparison and the trailingIS TRUEhad nowhere to go. Postfix IS predicates (IS [NOT] NULL / TRUE / FALSE / UNKNOWN / JSON) now chain onto the result of any earlier suffix in a loop.Two traps the loop has to avoid, both covered by a semantic guard (
isPostfixIsTestAhead) rather than first tokens:IS DISTINCT FROMis also IS-led but takes a right-hand operand; the guard only enters on TRUE/FALSE/UNKNOWN/NULL/JSON, soa IS DISTINCT FROM bstill resolves through the existing first-suffix dispatch.NOT NULLas a column constraint after a DEFAULT expression (CREATE TABLE t (a INT DEFAULT 1 > 0 NOT NULL, ...)) is inIsNullExpression's first set; the guard rejects it before the loop commits, so that path is unchanged.Test plan
SELECT * FROM t WHERE a > 0 IS TRUEparses and round-tripsSELECT * FROM t WHERE a IN (1, 2) IS FALSEparses and round-tripsSELECT * FROM t WHERE a IS NULL IS NOT TRUEchains both testsSELECT * FROM t WHERE a IS TRUE IS FALSEchains a test onto a testCREATE TABLE t (a INT DEFAULT 1 > 0 NOT NULL, b INT)keepsNOT NULLas a column constraint (existingColumnDefaultExpressionTest)