Adds ability to change compaction default in YAML

and switches to UCS for the trie unit test suite

Author: blambov

src/java/org/apache/cassandra/config/Config.java

@@ -1083,6 +1083,11 @@ public enum PaxosOnLinearizabilityViolation
     public volatile long min_tracked_partition_tombstone_count = 5000;
     public volatile boolean top_partitions_enabled = true;
 
+    /**
+     * Default compaction configuration, used if a table does not specify any.
+     */
+    public ParameterizedClass default_compaction = null;
+
     public static Supplier<Config> getOverrideLoadConfig()
     {
         return overrideLoadConfig;

src/java/org/apache/cassandra/config/DatabaseDescriptor.java

@@ -4677,4 +4677,9 @@ public static void setClientRequestSizeMetricsEnabled(boolean enabled)
     {
         return Objects.requireNonNull(sstableFormatFactories, "Forgot to initialize DatabaseDescriptor?");
     }
+
+    public static ParameterizedClass getDefaultCompaction()
+    {
+        return conf != null ? conf.default_compaction : null;
+    }
 }

src/java/org/apache/cassandra/schema/CompactionParams.java

@@ -30,6 +30,8 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import org.apache.cassandra.config.DatabaseDescriptor;
+import org.apache.cassandra.config.ParameterizedClass;
 import org.apache.cassandra.db.compaction.AbstractCompactionStrategy;
 import org.apache.cassandra.db.compaction.LeveledCompactionStrategy;
 import org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy;
@@ -84,8 +86,23 @@ public static Optional<TombstoneOption> forName(String name)
         ImmutableMap.of(Option.MIN_THRESHOLD.toString(), Integer.toString(DEFAULT_MIN_THRESHOLD),
                         Option.MAX_THRESHOLD.toString(), Integer.toString(DEFAULT_MAX_THRESHOLD));
 
-    public static final CompactionParams DEFAULT =
-        new CompactionParams(SizeTieredCompactionStrategy.class, DEFAULT_THRESHOLDS, DEFAULT_ENABLED, DEFAULT_PROVIDE_OVERLAPPING_TOMBSTONES);
+    public static final CompactionParams DEFAULT;
+    static
+    {
+        ParameterizedClass defaultCompaction = DatabaseDescriptor.getDefaultCompaction();
+        if (defaultCompaction == null)
+        {
+            DEFAULT = new CompactionParams(SizeTieredCompactionStrategy.class,
+                                           DEFAULT_THRESHOLDS,
+                                           DEFAULT_ENABLED,
+                                           DEFAULT_PROVIDE_OVERLAPPING_TOMBSTONES);
+        }
+        else
+        {
+            DEFAULT = create(classFromName(defaultCompaction.class_name),
+                             defaultCompaction.parameters);
+        }
+    }
 
     private final Class<? extends AbstractCompactionStrategy> klass;
     private final ImmutableMap<String, String> options;

test/conf/trie_memtable.yaml

@@ -15,6 +15,13 @@
 # specific language governing permissions and limitations
 # under the License.
 
+# Change default memtable implementation to TrieMemtable
 # Note: this attaches at the end of cassandra.yaml, where the memtable configuration setting must be.
         default:
             inherits: trie
+
+# Change default compaction to UCS
+default_compaction:
+  class_name: UnifiedCompactionStrategy
+  parameters:
+    base_shard_count: 1

test/unit/org/apache/cassandra/cql3/statements/DescribeStatementTest.java

@@ -18,6 +18,7 @@
 package org.apache.cassandra.cql3.statements;
 
 import java.util.Iterator;
+import java.util.Map;
 import java.util.Optional;
 
 import com.google.common.collect.ImmutableList;
@@ -34,9 +35,11 @@
 
 import org.apache.cassandra.config.DatabaseDescriptor;
 import org.apache.cassandra.cql3.CQLTester;
+import org.apache.cassandra.cql3.CqlBuilder;
 import org.apache.cassandra.dht.Token;
 import org.apache.cassandra.locator.InetAddressAndPort;
 import org.apache.cassandra.locator.TokenMetadata;
+import org.apache.cassandra.schema.CompactionParams;
 import org.apache.cassandra.schema.Schema;
 import org.apache.cassandra.schema.TableId;
 import org.apache.cassandra.service.StorageService;
@@ -844,21 +847,26 @@ private static String tableParametersCql()
                "    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}\n" +
                "    AND cdc = false\n" +
                "    AND comment = ''\n" +
-               "    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}\n" +
+               "    AND compaction = " + cqlQuoted(CompactionParams.DEFAULT.asMap()) + "\n" +
                "    AND compression = {'chunk_length_in_kb': '16', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}\n" +
                "    AND memtable = 'default'\n" +
                "    AND crc_check_chance = 1.0\n" +
                "    AND default_time_to_live = 0\n" +
                "    AND extensions = {}\n" +
                "    AND gc_grace_seconds = 864000\n" +
-               "    AND incremental_backups = true\n" + 
+               "    AND incremental_backups = true\n" +
                "    AND max_index_interval = 2048\n" +
                "    AND memtable_flush_period_in_ms = 0\n" +
                "    AND min_index_interval = 128\n" +
                "    AND read_repair = 'BLOCKING'\n" +
                "    AND speculative_retry = '99p';";
     }
 
+    private static String cqlQuoted(Map<String, String> map)
+    {
+        return new CqlBuilder().append(map).toString();
+    }
+
     private static String mvParametersCql()
     {
         return "additional_write_policy = '99p'\n" +
@@ -867,7 +875,7 @@ private static String mvParametersCql()
                "    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}\n" +
                "    AND cdc = false\n" +
                "    AND comment = ''\n" +
-               "    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}\n" +
+               "    AND compaction = " + cqlQuoted(CompactionParams.DEFAULT.asMap()) + "\n" +
                "    AND compression = {'chunk_length_in_kb': '16', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}\n" +
                "    AND memtable = 'default'\n" +
                "    AND crc_check_chance = 1.0\n" +