[CALCITE-7440] Preserve correlated scope mapping in RelToSqlConverter

[bvolpato]

Summary

RelToSqlConverter failed during PostgreSQL round-trip validation when semi-join rewrites introduced a correlated filter with an unresolved correlation id.

Reproduction query

WITH product_keys AS (
  SELECT p."product_id",
         (SELECT MAX(p3."product_id")
          FROM "foodmart"."product" p3
          WHERE p3."product_id" = p."product_id") AS "mx"
  FROM "foodmart"."product" p
)
SELECT DISTINCT pk."product_id"
FROM product_keys pk
LEFT JOIN "foodmart"."product" p2 USING ("product_id")
WHERE pk."product_id" IN (
  SELECT p4."product_id"
  FROM "foodmart"."product" p4
)

Error before this PR

java.lang.NullPointerException: variable $cor1 is not found
  at org.apache.calcite.rel.rel2sql.SqlImplementor.getAliasContext(SqlImplementor.java:1590)

Fix

Register missing RexCorrelVariable ids while visiting filter conditions, without overriding existing correlation mappings.

Test

• Added RelToSqlConverterTest.testPostgresqlRoundTripCorrelatedProjectWithSemiJoinRules
• Ran: ./gradlew :core:test --tests org.apache.calcite.rel.rel2sql.RelToSqlConverterTest
• Result: 563 passed, 0 failed

Disclaimer

The changes were done with the assistance of Codex (gpt-5.3-codex) in response to an actual bug when using Calcite in production. The changes were manually verified prior to sending this to review.

[xiedeyantu]

I ran this test on the main branch, and strangely it passed. Could you check if your case can reproduce the problem you mentioned?

  @Test void testPostgresqlRoundTripCorrelatedProjectWithSemiJoinRules() {
    final String query = "WITH product_keys AS (\n"
        + "  SELECT p.\"product_id\",\n"
        + "         (SELECT MAX(p3.\"product_id\")\n"
        + "          FROM \"foodmart\".\"product\" p3\n"
        + "          WHERE p3.\"product_id\" = p.\"product_id\") AS \"mx\"\n"
        + "  FROM \"foodmart\".\"product\" p\n"
        + ")\n"
        + "SELECT DISTINCT pk.\"product_id\"\n"
        + "FROM product_keys pk\n"
        + "LEFT JOIN \"foodmart\".\"product\" p2 USING (\"product_id\")\n"
        + "WHERE pk.\"product_id\" IN (\n"
        + "  SELECT p4.\"product_id\"\n"
        + "  FROM \"foodmart\".\"product\" p4\n"
        + ")";

    final RuleSet rules = RuleSets.ofList();
    final String generated = sql(query).withPostgresql().optimize(rules, null).exec();
    sql(generated).withPostgresql().exec();
  }

[xiedeyantu]

Please take a look at my description; you may not have solved my problem.

[bvolpato]

Thanks for the review! Updated this PR with both requested changes:

Reduced the regression to the minimal reproducer on main (empty rules was a mistake):

• FILTER_SUB_QUERY_TO_MARK_CORRELATE
• PROJECT_SUB_QUERY_TO_MARK_CORRELATE
• MARK_TO_SEMI_OR_ANTI_JOIN_RULE
• SEMI_JOIN_JOIN_TRANSPOSE

Added a plain round-trip test without extra rules:

• testPostgresqlRoundTripCorrelatedProject

Both new/updated tests pass locally in this branch.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
86.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud