[GitHub] [calcite] helloppx commented on a change in pull request #1680: [CALCITE-3621] Push down sort to DB, SQL of Sort rel contains explicit field name instead of * when sort is not top rel

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helloppx commented on a change in pull request #1680: [CALCITE-3621] Push down sort to DB, SQL of Sort rel contains explicit field name instead of * when sort is not top rel
URL: https://github.com/apache/calcite/pull/1680#discussion_r360756860
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java
 ##########
 @@ -634,6 +634,13 @@ public Result visit(Sort e) {
     }
     Result x = visitChild(0, e.getInput());
     Builder builder = x.builder(e, Clause.ORDER_BY);
+    if (builder.select.getSelectList() == null) {
 
 Review comment:
   When JdbcSort is used, a regression issue will be trigged: JdbcTest#testSelfJoinDifferentColumns()
   
   Following is the regression issue info:
   
   Input SQL: A
   select e1."full_name"
     from "foodmart"."employee" as e1
     join "foodmart"."employee" as e2 on e1."first_name" = e2."last_name"
   order by e1."last_name" limit 3
   
   Best REL:
   JdbcToEnumerableConverter
   --JdbcProject(full_name=[$1], last_name=[$3])
   ----JdbcSort(sort0=[$3], dir0=[ASC], fetch=[3])
   ------JdbcJoin(condition=[=($2, $0)], joinType=[inner])
   --------JdbcProject(last_name=[$3])
   ----------JdbcTableScan(table=[[foodmart, employee]])
   --------JdbcProject(full_name=[$1], first_name=[$2], last_name=[$3])
   ----------JdbcTableScan(table=[[foodmart, employee]])
   
   Output SQL: B
   SELECT "t2"."full_name", "t2"."last_name0" AS "last_name"
   FROM (SELECT *
   FROM (SELECT "last_name"
   FROM "foodmart"."employee") AS "t"
   INNER JOIN (SELECT "full_name", "first_name", "last_name"
   FROM "foodmart"."employee") AS "t0" ON "t"."last_name" = "t0"."first_name"
   ORDER BY "t0"."last_name" NULLS LAST
   LIMIT 3) AS "t2"
   
   After fix, output SQL: C
   SELECT "t2"."full_name", "t2"."last_name0" AS "last_name"
   FROM (SELECT "t"."last_name", "t0"."full_name", "t0"."first_name", "t0"."last_name" AS "last_name0"
   FROM (SELECT "last_name"
   FROM "foodmart"."employee") AS "t"
   INNER JOIN (SELECT "full_name", "first_name", "last_name"
   FROM "foodmart"."employee") AS "t0" ON "t"."last_name" = "t0"."first_name"
   ORDER BY "t0"."last_name" NULLS LAST
   LIMIT 3) AS "t2"
   
   SQL B is wrong, since "t2" is a subquery but it's select list is ambiguous. Database complains "last_name0" cannot be found in schema. 
   that is, the SQL of RelToSqlConverter#visit(Sort e) generated should has explicit select list when the Sort is not outter rel.
   

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