fix: fdw/external support filter pushdown for numeric columns with integer constants#103
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MisterRaindrop merged 4 commits intoapache:mainfrom Apr 19, 2026
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When a numeric column is compared with an integer constant (e.g., biz_dt = 20260331), PostgreSQL wraps the constant in an implicit type cast FuncExpr (int4 -> numeric). The filter extraction code only recognized plain Const nodes, causing these filters to be dropped and resulting in full table scans on the source. Use eval_const_expressions() to evaluate implicit cast expressions back to plain Const nodes before filter extraction.
The previous commit fixed fdw/pxf_filter.c but the external table code path (external-table/src/pxffilters.c) has the same issue in opexpr_to_pxffilter(). Apply the same eval_const_expressions() fix to handle implicit type casts on constants.
Extend FilterPushDownTest / FDW_FilterPushDownTest regression suites with c3 = 5 and c3 < 5 to exercise the '=' and '<' operators with an integer constant against a numeric column — the original scenario behind the pushdown fix (biz_dt = 20260331) was previously only covered for >, <=, >=, <> and BETWEEN. Also sync FilterPushDownTest.sql to include the int-const block in both test segments, matching the expected output.
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Change logs
When a numeric column is compared with an integer constant (e.g.,
biz_dt = 20260331), PostgreSQL wraps the constant in an implicit
type cast FuncExpr (int4 -> numeric). The filter extraction code
only recognized plain Const nodes, causing these filters to be
dropped and resulting in full table scans on the source.
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