Document limitation: cannot flatten OR/AND chains in EXPLAIN output#92
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kyleconroy merged 2 commits intomainfrom Dec 30, 2025
Merged
Document limitation: cannot flatten OR/AND chains in EXPLAIN output#92kyleconroy merged 2 commits intomainfrom
kyleconroy merged 2 commits intomainfrom
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The 02711_trim_aliases test expects OR chains like "a OR b OR c" to be flattened to or(a, b, c) with 3 children. However, tests like 01661_join_complex expect "(a OR b) OR c" to remain nested as or(or(a,b), c) with 2 children. Both SQL patterns produce identical parse trees due to left-associative parsing. Our parser doesn't track explicit parenthesization, but ClickHouse's EXPLAIN output distinguishes between them based on the original SQL syntax. Since we cannot tell implicit grouping apart from explicit parentheses at the AST level, any fix for 02711 would break 01661 (and vice versa). The 02711_trim_aliases test remains in explain_todo as this is a fundamental limitation of our parser architecture.
…ization Add a Parenthesized field to BinaryExpr in the AST to track when an expression was wrapped in explicit parentheses. This allows the EXPLAIN output to correctly distinguish between: - "a OR b OR c" → or(a, b, c) [flattened, no explicit parens] - "(a OR b) OR c" → or(or(a,b), c) [nested, explicit parens preserved] Changes: - ast/ast.go: Add Parenthesized field to BinaryExpr - parser/expression.go: Set Parenthesized=true when parsing grouped expressions - internal/explain/expressions.go: Add collectLogicalOperands() that respects the Parenthesized flag when flattening OR/AND chains This fixes the 02711_trim_aliases test and many other tests that were previously in explain_todo due to incorrect OR/AND chain handling.
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The 02711_trim_aliases test expects OR chains like "a OR b OR c" to be
flattened to or(a, b, c) with 3 children. However, tests like 01661_join_complex
expect "(a OR b) OR c" to remain nested as or(or(a,b), c) with 2 children.
Both SQL patterns produce identical parse trees due to left-associative parsing.
Our parser doesn't track explicit parenthesization, but ClickHouse's EXPLAIN
output distinguishes between them based on the original SQL syntax.
Since we cannot tell implicit grouping apart from explicit parentheses at the
AST level, any fix for 02711 would break 01661 (and vice versa).
The 02711_trim_aliases test remains in explain_todo as this is a fundamental
limitation of our parser architecture.