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DuckDB: parse slices with omitted bounds or a step - #2794
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`l[2:]`, `l[:]` and `l[-5:]` failed, `l[2:3]` parsed as the JSON path `2 : 3` and `l[:2]` as the numeric bind `:2`. Inside a subscript, a `:` now separates the bounds of a slice rather than starting a JSON path. Slices also take DuckDB's optional step, `l[1:5:2]`, where a `-` stop stands for the end of the list, `l[1:-:2]`. `RangeExpression` and `ArrayExpression` gain a step and accept missing bounds.
guizmaii
marked this pull request as draft
October 13, 2026 07:58
guizmaii
changed the title
`l[(SELECT c:a FROM t)]`, `l[f(x, c:a)]` and `l[CASE WHEN c:a = 1 ...]` failed: the subscript depth disabled the JSON path operator in every expression nested in the subscript. Only a `:` at the subscript's own top level, outside brackets, braces, parentheses and CASE, now separates slice bounds.
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For DuckDB, whose lists and strings support slices with omitted bounds and a step (docs).
Inside a subscript,
:was read as the Snowflake JSON path operator, so slices did not parse as slices:l[2:3]JsonExpression2 : 3l[:2]NumericBind:2l[2:],l[:],l[-5:]l[1:5:2],l[1:-:2](DuckDB step,-= end):at the top level of a subscript (col[...],expr[...]), outside any brackets, braces, parentheses or CASE opened in it, separates slice bounds instead of starting a JSON path. JSON paths elsewhere are unchanged:c:a[1],l[(SELECT c:a FROM t)],l[f(c:a)],l[ARRAY[c:a]].l[:name]/l[:1]are now slices up toname/1, no longer a JDBC named parameter / numeric bind; Snowflake'sl[v:i]is now a slice. Both follow PostgreSQL and DuckDB slice syntax.RangeExpression(column subscripts) andArrayExpression(other subscripts) gain a step and accept missing bounds. A missing stop before a step deparses as-, sincel[1::2]would lex as a cast.TablesNamesFinderTraversalTestasserted theJsonExpressionparse off()[1:2]; it now asserts the slice bounds.checkGrammarAmbiguity: no conflicts../gradlew check: 10,121 tests, 0 failures.test/sql, 70,729 statements): 36 more parse, none less.