chore(isthmus): remove dead code (#604)

Since the use of DdlSqlToRelConverter was added to SubstraitSqlToCalcite
in commit 260a1c4, the original
invocation of SqlToRelConverter that was left as a fallback when it
returns null is never called. The reason is that DdlSqlToRelConverter
itself already falls back to calling SqlToRelConverter so it never
returns null. This means that removeRedundantProjects is never applied
to the Rel structure since this only occurs in the uncalled fallback
path. All tests continue to pass, which indicates that this optimiation
is unnecessary.

If it required in the future, it might be better written as follows to
provide flexibility in the rules applied:

static RelRoot applyPlannerRules(RelRoot root, RelOptRule... rules) {
  HepProgramBuilder builder = HepProgram.builder();
  for (RelOptRule rule : rules) {
    builder.addRuleInstance(rule);
  }

  HepPlanner planner = new HepPlanner(builder.build());
  planner.setRoot(root.rel);

  RelNode optimizedExpression = planner.findBestExp();

  return root.withRel(optimizedExpression);
}

Signed-off-by: Mark S. Lewis <Mark.S.Lewis@outlook.com>

Author: bestbeforetoday

isthmus/src/main/java/io/substrait/isthmus/sql/SubstraitSqlToCalcite.java

@@ -13,7 +13,6 @@
 import org.apache.calcite.prepare.Prepare;
 import org.apache.calcite.rel.RelNode;
 import org.apache.calcite.rel.RelRoot;
-import org.apache.calcite.rel.rules.CoreRules;
 import org.apache.calcite.rex.RexBuilder;
 import org.apache.calcite.sql.SqlNode;
 import org.apache.calcite.sql.parser.SqlParseException;
@@ -129,21 +128,9 @@ static List<RelRoot> convert(
             cluster,
             StandardConvertletTable.INSTANCE,
             SqlToRelConverter.CONFIG);
-    // apply validation
-    boolean needsValidation = true;
-    // query is the root of the tree
-    boolean top = true;
     DdlSqlToRelConverter ddlSqlToRelConverter = new DdlSqlToRelConverter(converter);
     return sqlNodes.stream()
-        .map(
-            sqlNode -> {
-              RelRoot relRoot = sqlNode.accept(ddlSqlToRelConverter);
-              if (relRoot == null) {
-                relRoot =
-                    removeRedundantProjects(converter.convertQuery(sqlNode, needsValidation, top));
-              }
-              return relRoot;
-            })
+        .map(sqlNode -> sqlNode.accept(ddlSqlToRelConverter))
         .collect(Collectors.toList());
   }
 
@@ -154,18 +141,4 @@ static RelOptCluster createDefaultRelOptCluster() {
     RelOptPlanner emptyPlanner = new HepPlanner(program);
     return RelOptCluster.create(emptyPlanner, rexBuilder);
   }
-
-  static RelRoot removeRedundantProjects(RelRoot root) {
-    return root.withRel(removeRedundantProjects(root.rel));
-  }
-
-  static RelNode removeRedundantProjects(RelNode root) {
-    // The Calcite RelBuilder, when constructing Project that does not modify its inputs in any way,
-    // simply elides it. The PROJECT_REMOVE rule can be used to remove such projects from Rel trees.
-    // This facilitates roundtrip testing.
-    HepProgram program = HepProgram.builder().addRuleInstance(CoreRules.PROJECT_REMOVE).build();
-    HepPlanner planner = new HepPlanner(program);
-    planner.setRoot(root);
-    return planner.findBestExp();
-  }
 }