Github user sudheeshkatkam commented on a diff in the pull request:
https://github.com/apache/drill/pull/425#discussion_r63799682
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/DrillStatsTable.java
---
@@ -0,0 +1,161 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ * <p/>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p/>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.drill.exec.planner.common;
+
+import java.util.Map;
+
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Maps;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.RelVisitor;
+import org.apache.calcite.rel.core.TableScan;
+import org.apache.drill.exec.client.DrillClient;
+import org.apache.drill.exec.ops.QueryContext;
+import org.apache.drill.exec.planner.logical.DrillTable;
+import org.apache.drill.exec.proto.UserBitShared;
+import org.apache.drill.exec.server.DrillbitContext;
+import org.apache.drill.exec.server.rest.QueryWrapper.Listener;
+
+/**
+ * Wraps the stats table info including schema and tableName. Also
materializes stats from storage and keeps them in
+ * memory.
+ */
+public class DrillStatsTable {
+ private static final org.slf4j.Logger logger =
org.slf4j.LoggerFactory.getLogger(DrillStatsTable.class);
+
+ /**
+ * List of columns in stats table.
+ */
+ public static final String COL_COLUMN = "column";
+ public static final String COL_COMPUTED = "computed";
+ public static final String COL_STATCOUNT = "statcount";
+ public static final String COL_NDV = "ndv";
+
+ private final String schemaName;
+ private final String tableName;
+
+ private final Map<String, Long> ndv = Maps.newHashMap();
+ private double rowCount = -1;
+
+ private boolean materialized = false;
+
+ public DrillStatsTable(String schemaName, String tableName) {
+ this.schemaName = schemaName;
+ this.tableName = tableName;
+ }
+
+ /**
+ * Get number of distinct values of given column. If stats are not
present for the given column, a null is returned.
+ *
+ * Note: returned data may not be accurate. Accuracy depends on whether
the table data has changed after the
+ * stats are computed.
+ *
+ * @param col
+ * @return
+ */
+ public Double getNdv(String col) {
+ Preconditions.checkState(materialized, "Stats are not yet
materialized.");
+
+ final String upperCol = col.toUpperCase();
+ final Long ndvCol = ndv.get(upperCol);
+ if (ndvCol != null) {
+ return Math.min(ndvCol, rowCount);
+ }
+
+ return null;
+ }
+
+ /**
+ * Get row count of the table. Returns null if stats are not present.
+ *
+ * Note: returned data may not be accurate. Accuracy depends on whether
the table data has changed after the
+ * stats are computed.
+ *
+ * @return
+ */
+ public Double getRowCount() {
+ Preconditions.checkState(materialized, "Stats are not yet
materialized.");
+ return rowCount > 0 ? rowCount : null;
+ }
+
+ /**
+ * Read the stats from storage and keep them in memory.
+ * @param context
+ * @throws Exception
+ */
+ public void materialize(final QueryContext context) throws Exception {
+ if (materialized) {
+ return;
+ }
+
+ final String fullTableName = "`" + schemaName + "`.`" + tableName +
"`";
+ final String sql = "SELECT a.* FROM " + fullTableName + " AS a INNER
JOIN " +
+ "(SELECT `" + COL_COLUMN + "`, max(`" + COL_COMPUTED +"`) AS `" +
COL_COMPUTED + "` " +
+ "FROM " + fullTableName + " GROUP BY `" + COL_COLUMN + "`) AS b " +
+ "ON a.`" + COL_COLUMN + "` = b.`" + COL_COLUMN +"` and a.`" +
COL_COMPUTED + "` = b.`" + COL_COMPUTED + "`";
+
+ final DrillbitContext dc = context.getDrillbitContext();
+ try(final DrillClient client = new DrillClient(dc.getConfig(),
dc.getClusterCoordinator(), dc.getAllocator())) {
--- End diff --
Few questions here:
(1) How does this work when authentication is enabled?
(2) Why does this use a listener from the rest package?
(3) Are there alternative way to run this query?
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
