vlsi commented on a change in pull request #2363:
URL: https://github.com/apache/calcite/pull/2363#discussion_r591220447
##########
File path: core/src/test/java/org/apache/calcite/test/RelMetadataTest.java
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@@ -3412,4 +3414,41 @@ public String colType(RelNode rel, int column) {
assertThat(columnOrigin.getOriginTable().getRowType().getFieldNames().get(5),
equalTo("SAL"));
}
+
+ // ----------------------------------------------------------------------
+ // Tests for SortCpuCost
+ // ----------------------------------------------------------------------
+
+ @Test void testSortCpuCostOffsetLimit() {
+ final String sql = "select ename from emp order by ename limit 5 offset 5";
+ double cpuCost = EMP_SIZE * Math.log(10) * 4;
+ checkCpuCost(sql, cpuCost);
+ }
+
+ @Test void testSortCpuCostLimit() {
+ final String sql = "select ename from emp limit 10";
+ checkCpuCost(sql, 0d);
+ }
+
+ @Test void testSortCpuCostLimit0() {
+ final String sql = "select ename from emp order by ename limit 0";
+ checkCpuCost(sql, 0d);
+ }
+
+ @Test void testSortCpuCostLargeLimit() {
+ final String sql = "select ename from emp order by ename limit 10000";
+ double cpuCost = EMP_SIZE * Math.log(EMP_SIZE) * 4;
+ checkCpuCost(sql, cpuCost);
+ }
+
+ private void checkCpuCost(String sql, double expected) {
+ RelNode rel = convertSql(sql);
+ assertThat("query should be sort", rel instanceof LogicalSort);
+ final RelMetadataQuery mq = rel.getCluster().getMetadataQuery();
+ RelOptPlanner planner = new VolcanoPlanner();
+ RelOptCost cost = rel.computeSelfCost(planner, mq);
+ assertThat(cost, notNullValue());
+ final double result = cost.getCpu();
+ assertThat(result, is(expected));
Review comment:
Suppose I have never seen the test code, and I see the following failure
in the CI output:
```
Expected: not null
but: was null
java.lang.AssertionError:
Expected: not null
but: was null
```
What should I do? Why "expected not null"? Why "was null"? What exactly was
null?
The proper assertion failure should look like a good bug report rather than
"go figure out what went wrong".
Bad assertions and bad test code make maintenance much harder.
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