mihaibudiu commented on code in PR #3648:
URL: https://github.com/apache/calcite/pull/3648#discussion_r1477438271


##########
testkit/src/main/java/org/apache/calcite/test/SqlOperatorTest.java:
##########
@@ -6215,6 +6215,71 @@ void checkRegexpExtract(SqlOperatorFixture f0, 
FunctionAlias functionAlias) {
     f.checkNull("log(10, cast(null as real))");
   }
 
+  /** Test case for
+   * <a 
href="https://issues.apache.org/jira/browse/CALCITE-6224";>[CALCITE-6224]
+   * Add LOG@ function (enabled in MYSQL, Spark library)</a>. */
+  @Test void testLog2Func() {
+    final SqlOperatorFixture f0 = fixture();
+    final Consumer<SqlOperatorFixture> consumer = f -> {
+      f.setFor(SqlLibraryOperators.LOG2);
+      f.checkScalarApprox("log2(2)", "DOUBLE NOT NULL",
+          isWithin(1.0, 0.000001));
+      f.checkScalarApprox("log2(4)", "DOUBLE NOT NULL",
+          isWithin(2.0, 0.000001));
+      f.checkScalarApprox("log2(65536)", "DOUBLE NOT NULL",
+          isWithin(16.0, 0.000001));
+      f.checkScalarApprox("log2(-2)", "DOUBLE NOT NULL",
+          "NaN");
+      f.checkScalarApprox("log2(2/3)", "DOUBLE NOT NULL",
+          "-Infinity");
+      f.checkScalarApprox("log2(2.2)", "DOUBLE NOT NULL",
+          "1.1375035237499351");
+      f.checkScalarApprox("log2(0.5)", "DOUBLE NOT NULL",
+          "-1.0");
+      f.checkScalarApprox("log2(3)", "DOUBLE NOT NULL",
+          isWithin(1.5849625007211563, 0.000001));
+      f.checkNull("log2(cast(null as real))");
+    };
+    f0.forEachLibrary(list(SqlLibrary.MYSQL, SqlLibrary.SPARK), consumer);
+  }
+
+  /** Test case for
+   * <a 
href="https://issues.apache.org/jira/browse/CALCITE-6232";>[CALCITE-6232]
+   * Using fractions in LOG function does not return correct results</a>. */
+  @Test void testLogFuncByConvert() {
+    final SqlOperatorFixture f0 = fixture();
+    f0.setFor(SqlLibraryOperators.LOG, VmName.EXPAND);
+    final SqlOperatorFixture f = f0.withLibrary(SqlLibrary.BIG_QUERY);
+    f.checkScalarApprox("log(2.0/3, 2)", "DOUBLE NOT NULL",

Review Comment:
   If a function is part of a dialect, it should definitely have the same 
behavior as the dialect requires. This should also be documented. We may be 
dealing with multiple LOG functions, with slightly different behaviors. That's 
why it is very important to test all corner cases, including writing negative 
tests.



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