fix: check and mutate should check for existence on empty byte values (#3480)

Author: kolea2

CONTRIBUTING.md

@@ -24,6 +24,7 @@ again.
 
    ```sh
    mvn clean verify \
+       -Penable-integration-tests \
        -PbigtableIntegrationTest \
        -Dgoogle.bigtable.project.id=[your cloud project id] \
        -Dgoogle.bigtable.instance.id=[your cloud bigtable instance id]
@@ -33,6 +34,7 @@ again.
 
    ```sh
    mvn clean verify \
+       -Penable-integration-tests \
        -PbigtableIntegrationTestH2 \
        -Dgoogle.bigtable.project.id=[your cloud project id] \
        -Dgoogle.bigtable.instance.id=[your cloud bigtable instance id]

bigtable-client-core-parent/bigtable-hbase-integration-tests-common/src/test/java/com/google/cloud/bigtable/hbase/AbstractTestCheckAndMutate.java

@@ -55,10 +55,10 @@ public void testCheckAndPutSameQual() throws Exception {
       Assert.assertFalse(
           "Column doesn't exist. Should fail.",
           checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual, value2, put1));
-      Assert.assertFalse(
-          "Column still doesn't exist. Should fail.",
+      Assert.assertTrue(
+          "Column should be created on zero bytes.",
           checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual, ZERO_BYTES, put1));
-      Assert.assertTrue(checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual, null, put1));
+      Assert.assertFalse(checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual, null, put1));
 
       // Fail on null check, now there's a value there
       Put put2 = new Put(rowKey).addColumn(SharedTestEnvRule.COLUMN_FAMILY, qual, value2);
@@ -153,8 +153,8 @@ public void testCheckAndPutDiffQual() throws Exception {
     Assert.assertFalse(
         "Column doesn't exist. Should fail.",
         checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual2, value2, put1));
-    Assert.assertFalse(
-        "Column still doesn't exist. Should fail.",
+    Assert.assertTrue(
+        "Column should be created on zero bytes.",
         checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual2, ZERO_BYTES, put1));
     Assert.assertTrue(checkAndPut(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual2, null, put1));
 
@@ -172,7 +172,7 @@ public void testCheckAndPutDiffQual() throws Exception {
     Get get = new Get(rowKey);
     get.setMaxVersions(5);
     Result result = table.get(get);
-    Assert.assertEquals("Should be two results", 2, result.size());
+    Assert.assertEquals(3, result.size());
     Assert.assertArrayEquals(
         value1,
         CellUtil.cloneValue(result.getColumnLatestCell(SharedTestEnvRule.COLUMN_FAMILY, qual1)));
@@ -199,8 +199,8 @@ public void testCheckAndDeleteDiffQual() throws Exception {
     Assert.assertFalse(
         "Column doesn't exist. Should fail.",
         checkAndDelete(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual2, value2, delete));
-    Assert.assertFalse(
-        "Column still doesn't exist. Should fail.",
+    Assert.assertTrue(
+        "Column should be created on zero bytes.",
         checkAndDelete(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual2, ZERO_BYTES, delete));
     Assert.assertTrue(checkAndDelete(rowKey, SharedTestEnvRule.COLUMN_FAMILY, qual2, null, delete));
 
@@ -296,8 +296,8 @@ public void testCheckAndMutate() throws Exception {
         "Column doesn't exist. Should fail.",
         checkAndMutate(
             rowKey, SharedTestEnvRule.COLUMN_FAMILY, qualCheck, CompareOp.EQUAL, valueCheck, rm));
-    Assert.assertFalse(
-        "Column still doesn't exist. Should fail.",
+    Assert.assertTrue(
+        "Column should be created on zero bytes",
         checkAndMutate(
             rowKey, SharedTestEnvRule.COLUMN_FAMILY, qualCheck, CompareOp.EQUAL, ZERO_BYTES, rm));
     Assert.assertTrue(

bigtable-client-core-parent/bigtable-hbase/src/main/java/com/google/cloud/bigtable/hbase/adapters/CheckAndMutateUtil.java

@@ -217,7 +217,7 @@ public ConditionalRowMutation build() {
       scan.setMaxVersions(1);
       scan.addColumn(family, qualifier);
 
-      if (value == null || checkNonExistence) {
+      if (value == null || value.length == 0 || checkNonExistence) {
         // See ifMatches javadoc for more information on this
         if (CompareOp.NOT_EQUAL.equals(compareOp)) {
           // check for existence