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https://issues.apache.org/jira/browse/DRILL-1328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15213141#comment-15213141
]
ASF GitHub Bot commented on DRILL-1328:
---------------------------------------
Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/425#discussion_r57517236
--- 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) {
--- End diff --
When updating the drill stats file on the filesystem, similar to metadata
cache we should add a check: recompute stats only if the directory modification
time is later than the last stats timestamp. No need to recompute if stats is
not stale.
> Support table statistics
> ------------------------
>
> Key: DRILL-1328
> URL: https://issues.apache.org/jira/browse/DRILL-1328
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Cliff Buchanan
> Fix For: Future
>
> Attachments: 0001-PRE-Set-value-count-in-splitAndTransfer.patch
>
>
> This consists of several subtasks
> * implement operators to generate statistics
> * add "analyze table" support to parser/planner
> * create a metadata provider to allow statistics to be used by optiq in
> planning optimization
> * implement statistics functions
> Right now, the bulk of this functionality is implemented, but it hasn't been
> rigorously tested and needs to have some definite answers for some of the
> parts "around the edges" (how analyze table figures out where the table
> statistics are located, how a table "append" should work in a read only file
> system)
> Also, here are a few known caveats:
> * table statistics are collected by creating a sql query based on the string
> path of the table. This should probably be done with a Table reference.
> * Case sensitivity for column statistics is probably iffy
> * Math for combining two column NDVs into a joint NDV should be checked.
> * Schema changes aren't really being considered yet.
> * adding getDrillTable is probably unnecessary; it might be better to do
> getTable().unwrap(DrillTable.class)
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