[GitHub] [calcite] julianhyde commented on a change in pull request #1554: [CALCITE-3462] Add method in RelBuilder for conveniently projecting out expressions

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julianhyde commented on a change in pull request #1554: [CALCITE-3462] Add method in RelBuilder for conveniently projecting out expressions
URL: https://github.com/apache/calcite/pull/1554#discussion_r355708215
 
 

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 File path: core/src/main/java/org/apache/calcite/tools/RelBuilder.java
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 @@ -1259,15 +1255,33 @@ public RelBuilder projectPlus(RexNode... nodes) {
     return projectPlus(ImmutableList.copyOf(nodes));
   }
 
-  /** Creates a {@link Project} of all original fields, plus the given list of
+  /** Creates a {@link Project} of all original fields, plus the given
    * expressions. */
   public RelBuilder projectPlus(Iterable<RexNode> nodes) {
     final ImmutableList.Builder<RexNode> builder = ImmutableList.builder();
     return project(builder.addAll(fields()).addAll(nodes).build());
   }
 
-  /** Creates a {@link Project} of the given list
-   * of expressions, using the given names.
+  /** Creates a {@link Project} of all original fields, except the given
+   * expressions. */
+  public RelBuilder projectExcept(RexNode... expressions) {
+    return projectExcept(ImmutableList.copyOf(expressions));
+  }
+
+  /** Creates a {@link Project} of all original fields, except the given
+   * expressions. */
+  public RelBuilder projectExcept(Iterable<RexNode> expressions) {
+    List<RexNode> allExpressions = new ArrayList<>(fields());
+    for (RexNode excludeExp : expressions) {
+      if (!allExpressions.remove(excludeExp)) {
+        throw RESOURCE.expressionNotFound(excludeExp.toString()).ex();
 
 Review comment:
   My vote would be to throw IllegalArgumentException, not throw RESOURCE.something. This is an API error, not a user error.
   
   Don't make too much effort to accommodate people who are using the API incorrectly. Make the specification as simple as possible, and if people use it wrong, throw. 
   
   The simplest thing is probably `Collections.removeAll(Collection)`. Keep the argument as type `Iterable`, but cast or convert it to a collection.

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