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Commit & Pull Request Guidelines

Commits

  • Use a Conventional-style subject such as fix(storage): avoid stale snapshot (#19174) or feat: support self join elimination (#19169).
  • Keep the first line imperative and under 72 characters.
  • Keep each commit scoped to one logical change set.
  • Include formatting and linting updates in the same patch when they belong to the change.

Pull Requests

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  • Outline motivation, implementation notes, and validation commands.
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Example PR Description

I hereby agree to the terms of the CLA available at: https://docs.databend.com/dev/policies/cla/

## Summary

- Enable table functions like `generate_series` and `range` to accept scalar subqueries as arguments
- Return NULL for empty scalar subqueries to align with existing scalar subquery semantics

## Changes

This PR enables SQL like:

```sql
SELECT generate_series AS install_date
FROM generate_series(
    (SELECT count() FROM numbers(10))::int,
    (SELECT count() FROM numbers(39))::int
);

Previously, table function arguments could only be constants. Now they can be scalar subqueries that return a single value.

Implementation

  1. Added contains_subquery() function to detect subqueries in AST expressions
  2. Added execute_subquery_for_scalar() to execute and extract scalar values from subqueries
  3. Modified bind_table_args to try constant folding first, then fall back to subquery execution
  4. The subquery executor is passed from the binder to enable runtime evaluation
  5. Returns Scalar::Null for empty subquery results (aligns with LeftSingleJoin behavior)

Tests

  • Unit Test
  • Logic Test
  • Benchmark Test
  • No Test - Pair with the reviewer to explain why

Added tests in 02_0063_function_generate_series.test for:

  • generate_series with subquery arguments
  • range with subquery arguments

Type of change

  • New feature (non-breaking change which adds functionality)

This change is Reviewable