[GitHub] [calcite] amaliujia commented on a change in pull request #1587: [CALCITE-3272] Support TUMBLE as Table Value Function

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amaliujia commented on a change in pull request #1587: [CALCITE-3272] Support TUMBLE as Table Value Function
URL: https://github.com/apache/calcite/pull/1587#discussion_r347158057
 
 

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 File path: core/src/main/java/org/apache/calcite/adapter/enumerable/RexToLixTranslator.java
 ##########
 @@ -940,6 +956,49 @@ public static Expression translateLiteral(
     return list;
   }
 
+  private List<Expression> translateTableFunctionCall(RexCall rexCall, RelNode input) {
+    if (rexCall.op.getKind() == SqlKind.TUMBLE) {
+      // construct a input ref over watermarked column.
+      // Before DESCRIPTOR is implemented, the second parameter of TUMBLE
+      // is a string, which is one of the column from input.
+      assert rexCall.getOperands().get(1) instanceof RexLiteral;
+      String watermarkedColumnName =
+          ((RexLiteral) rexCall.getOperands().get(1)).getValueAs(String.class);
+      int watermarkedColumnIndex = -1;
+      List<RexNode> schemaForwardInputRefs = new ArrayList<>();
+      for (int i = 0; i < input.getRowType().getFieldCount(); i++) {
+        if (watermarkedColumnName.equals(input.getRowType().getFieldNames().get(i))) {
+          watermarkedColumnIndex = i;
+        }
+        schemaForwardInputRefs.add(builder.makeInputRef(input, i));
+      }
+      assert watermarkedColumnIndex > -1
+          && watermarkedColumnIndex < input.getRowType().getFieldCount();
+
+      List<Expression> translatedOperands = translateList(schemaForwardInputRefs);
+
+      // convert the third parameter, which should be a literal for an interval.
+      assert rexCall.getOperands().get(2) instanceof RexLiteral;
+      Expression intervalExpression = translate(rexCall.getOperands().get(2));
+
+      List<Expression> translatedOperandsForTumble = new ArrayList<>();
+      translatedOperandsForTumble.add(translatedOperands.get(watermarkedColumnIndex));
+      translatedOperandsForTumble.add(intervalExpression);
+      // compute the window_start
+      MethodNameImplementor windowStartMethod = new MethodNameImplementor("tumbleWindowStart");
 
 Review comment:
   I found it was hard to add these to `RexImpTable` because one operator has two implementor: window_start and window_end.
   
   For TUMBLE and HOP, a workaround is only provide implementor for window_start and later compute window_end by window_start + window_size. However, it won't work for `SESSION`. 

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