[GitHub] [calcite] vlsi commented on a change in pull request #2330: [CALCITE-4465] Estimate the number of distinct values by predicates

[GitBox <gi...@apache.org>]

vlsi commented on a change in pull request #2330:
URL: https://github.com/apache/calcite/pull/2330#discussion_r560953103



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File path: core/src/test/java/org/apache/calcite/rex/RexProgramTest.java
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@@ -2857,6 +2857,108 @@ private void checkSarg(String message, Sarg sarg,
         is(2), is("Sarg[[3..8], [10..20]]"));
   }
 
+  /** Tests {@link Sarg#numDistinctVals(RelDataType)}. */
+  @Test void testSargNdv() {
+    RelDataType nonNullableInt = typeFactory.createSqlType(SqlTypeName.INTEGER);
+    RelDataType nullableInt = typeFactory.createTypeWithNullability(nonNullableInt, true);
+
+    RelDataType nonNullableFloat = typeFactory.createSqlType(SqlTypeName.FLOAT);
+    RelDataType nullableFloat = typeFactory.createTypeWithNullability(nonNullableFloat, true);
+
+    // point: 10 (non-nullable)
+    Sarg sarg = Sarg.of(false,
+        ImmutableRangeSet.of(Range.closed(10, 10)));
+    assertThat(sarg.numDistinctVals(nonNullableInt), is(1.0));

Review comment:
       Could you please factor this to a helper method that receives `sarg`, `type`, and the expected matcher?
   
   Then the error message could include `sarg + ".numDistinctVals(" + type + ")"` so the developers could see the inputs that produced invalid output.
   
   The current assertion failures would look like "expected 1.0 got 1.5", and it would be hard to tell what is going on.
   
   
   An alternative option is to split assertions to individual tests (e.g. parameterized)




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