[ 
https://issues.apache.org/jira/browse/DRILL-1328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15213138#comment-15213138
 ] 

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_r57517122
  
    --- Diff: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/StatisticsAggrFunctions.java
 ---
    @@ -0,0 +1,295 @@
    
+/*******************************************************************************
    + * 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.
    + 
******************************************************************************/
    +
    +/*
    + * This class is automatically generated from AggrTypeFunctions2.tdd using 
FreeMarker.
    + */
    +
    +package org.apache.drill.exec.expr.fn.impl;
    +
    +import io.netty.buffer.DrillBuf;
    +import org.apache.drill.exec.expr.DrillAggFunc;
    +import org.apache.drill.exec.expr.DrillSimpleFunc;
    +import org.apache.drill.exec.expr.annotations.FunctionTemplate;
    +import 
org.apache.drill.exec.expr.annotations.FunctionTemplate.NullHandling;
    +import 
org.apache.drill.exec.expr.annotations.FunctionTemplate.FunctionScope;
    +import org.apache.drill.exec.expr.annotations.Output;
    +import org.apache.drill.exec.expr.annotations.Param;
    +import org.apache.drill.exec.expr.annotations.Workspace;
    +import org.apache.drill.exec.expr.holders.BigIntHolder;
    +import org.apache.drill.exec.expr.holders.NullableBigIntHolder;
    +import org.apache.drill.exec.expr.holders.NullableVarBinaryHolder;
    +import org.apache.drill.exec.expr.holders.ObjectHolder;
    +import org.apache.drill.exec.vector.complex.reader.FieldReader;
    +
    +import javax.inject.Inject;
    +
    +@SuppressWarnings("unused")
    +public class StatisticsAggrFunctions {
    +  static final org.slf4j.Logger logger = 
org.slf4j.LoggerFactory.getLogger(StatisticsAggrFunctions.class);
    +
    +  @FunctionTemplate(name = "statcount", scope = 
FunctionTemplate.FunctionScope.POINT_AGGREGATE)
    +  public static class StatCount implements DrillAggFunc {
    +    @Param
    +    FieldReader in;
    +    @Workspace
    +    BigIntHolder count;
    +    @Output
    +    NullableBigIntHolder out;
    +
    +    @Override
    +    public void setup() {
    +      count = new BigIntHolder();
    +    }
    +
    +    @Override
    +    public void add() {
    +      count.value++;
    +    }
    +
    +    @Override
    +    public void output() {
    +      out.isSet = 1;
    +      out.value = count.value;
    +    }
    +
    +    @Override
    +    public void reset() {
    +      count.value = 0;
    +    }
    +  }
    +
    +  @FunctionTemplate(name = "nonnullstatcount", scope = 
FunctionTemplate.FunctionScope.POINT_AGGREGATE)
    +  public static class NonNullStatCount implements DrillAggFunc {
    +    @Param
    +    FieldReader in;
    +    @Workspace
    +    BigIntHolder count;
    +    @Output
    +    NullableBigIntHolder out;
    +
    +    @Override
    +    public void setup() {
    +      count = new BigIntHolder();
    +    }
    +
    +    @Override
    +    public void add() {
    +      if (in.isSet()) {
    +        count.value++;
    +      }
    +    }
    +
    +    @Override
    +    public void output() {
    +      out.isSet = 1;
    +      out.value = count.value;
    +    }
    +
    +    @Override
    +    public void reset() {
    +      count.value = 0;
    +    }
    +  }
    +
    +  @FunctionTemplate(name = "hll", scope = 
FunctionTemplate.FunctionScope.POINT_AGGREGATE)
    +  public static class HllFieldReader implements DrillAggFunc {
    +    @Param
    +    FieldReader in;
    +    @Workspace
    +    ObjectHolder work;
    +    @Output
    +    NullableVarBinaryHolder out;
    +    @Inject
    +    DrillBuf buffer;
    +
    +    @Override
    +    public void setup() {
    +      work = new ObjectHolder();
    +      work.obj = new 
com.clearspring.analytics.stream.cardinality.HyperLogLog(10);
    +    }
    +
    +    @Override
    +    public void add() {
    +      if (work.obj != null) {
    +        com.clearspring.analytics.stream.cardinality.HyperLogLog hll =
    +            (com.clearspring.analytics.stream.cardinality.HyperLogLog) 
work.obj;
    +        int mode = in.getType().getMode().getNumber();
    +        int type = in.getType().getMinorType().getNumber();
    +
    +        switch (mode) {
    +          case 
org.apache.drill.common.types.TypeProtos.DataMode.OPTIONAL_VALUE:
    +            if (!in.isSet()) {
    +              hll.offer(null);
    +              break;
    +            }
    +            // fall through //
    +          case 
org.apache.drill.common.types.TypeProtos.DataMode.REQUIRED_VALUE:
    +            switch (type) {
    +              case 
org.apache.drill.common.types.TypeProtos.MinorType.VARCHAR_VALUE:
    +                hll.offer(in.readText().toString());
    +                break;
    +              default:
    +                work.obj = null;
    +            }
    +            break;
    +          default:
    +            work.obj = null;
    +        }
    +      }
    +    }
    +
    +    @Override
    +    public void output() {
    +      if (work.obj != null) {
    +        com.clearspring.analytics.stream.cardinality.HyperLogLog hll =
    +            (com.clearspring.analytics.stream.cardinality.HyperLogLog) 
work.obj;
    +
    +        try {
    +          byte[] ba = hll.getBytes();
    +          out.buffer = buffer.reallocIfNeeded(ba.length);
    +          out.start = 0;
    +          out.end = ba.length;
    +          out.buffer.setBytes(0, ba);
    +          out.isSet = 1;
    +        } catch (java.io.IOException e) {
    +          throw new 
org.apache.drill.common.exceptions.DrillRuntimeException("Failed to get 
HyperLogLog output", e);
    --- End diff --
    
    Throwing exception in the generated code is generally discouraged...or are 
we ok with RuntimeException ? 


> 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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