[jira] [Created] (CALCITE-7440) RelToSqlConverter throws NPE (variable $cor1 not found) for correlated projection after semi-join rewrites

[Bruno Volpato da Cunha (Jira)]

Bruno Volpato da Cunha created CALCITE-7440:
-----------------------------------------------

             Summary: RelToSqlConverter throws NPE (variable $cor1 not found) 
for correlated projection after semi-join rewrites
                 Key: CALCITE-7440
                 URL: https://issues.apache.org/jira/browse/CALCITE-7440
             Project: Calcite
          Issue Type: Bug
            Reporter: Bruno Volpato da Cunha


Reproduction query
{code:sql}
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
)
{code}

Optimizer rules
{code}
CoreRules.FILTER_SUB_QUERY_TO_CORRELATE
CoreRules.PROJECT_SUB_QUERY_TO_CORRELATE
CoreRules.JOIN_SUB_QUERY_TO_CORRELATE
CoreRules.FILTER_SUB_QUERY_TO_MARK_CORRELATE
CoreRules.PROJECT_SUB_QUERY_TO_MARK_CORRELATE
CoreRules.MARK_TO_SEMI_OR_ANTI_JOIN_RULE
CoreRules.PROJECT_TO_SEMI_JOIN
CoreRules.JOIN_TO_SEMI_JOIN
CoreRules.SEMI_JOIN_FILTER_TRANSPOSE
CoreRules.SEMI_JOIN_JOIN_TRANSPOSE
{code}

Generated SQL
{code:sql}
SELECT "t4"."product_id"
FROM (SELECT "$cor0"."product_id", "t1"."EXPR$0" AS "mx"
FROM "foodmart"."product" AS "$cor0",
LATERAL (SELECT MAX("product_id") AS "EXPR$0"
FROM "foodmart"."product"
WHERE "product_id" = "$cor0"."product_id") AS "t1"
WHERE EXISTS (SELECT 1
FROM (SELECT "product_id"
FROM "foodmart"."product") AS "t3"
WHERE "$cor0"."product_id" = "t3"."product_id")) AS "t4"
LEFT JOIN "foodmart"."product" AS "product2" ON "t4"."product_id" = 
"product2"."product_id"
GROUP BY "t4"."product_id"
{code}

Actual behavior
RelToSql conversion fails with:
{code}
java.lang.NullPointerException: variable $cor1 is not found
  at 
org.apache.calcite.rel.rel2sql.SqlImplementor.getAliasContext(SqlImplementor.java:1590)
{code}

Expected behavior
RelToSqlConverter should preserve correlation scope and generate valid SQL for 
this rule pipeline, without missing correlation variables.

Environment
- Calcite main branch (1.42.0-SNAPSHOT)
- RelToSqlConverterTest with PostgreSQL dialect
- Java 21



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