[
https://issues.apache.org/jira/browse/DRILL-4735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16089662#comment-16089662
]
Arina Ielchiieva commented on DRILL-4735:
-----------------------------------------
Fix will cover the following aspects:
1. {{ConvertCountToDirectScan}} will be able to distinguish between implicit /
directory and non-existent columns, relates to current Jira DRILL-4735.
To achieve this `Agg_on_scan` and `Agg_on_proj_on_scan` rules will take new
parameter in constructor {{OptimizerRulesContext}}, similar for [prune scan
rules|https://github.com/apache/drill/blob/3e8b01d5b0d3013e3811913f0fd6028b22c1ac3f/exec/java-exec/src/main/java/org/apache/drill/exec/planner/PlannerPhase.java#L345].
It will help to find out if column is implicit / directory or not.
{{OptimizerRulesContext}} has access to session options through
{{PlannerSettings}} which are crucial for defining current implicit / directory
column names. In case when [GroupScan will return column value as
0|https://github.com/apache/drill/blob/3e8b01d5b0d3013e3811913f0fd6028b22c1ac3f/exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/ConvertCountToDirectScan.java#L140],
we'll check if this column implicit / directory or not. If not, we'll proceed
with applying our rule.
2. {{ConvertCountToDirectScan}} rule to be applicable for 2 or more COUNT
aggregates, relates to DRILL-1691.
When column statistics is available we use {{PojoRecordReader}} to return its
value. {{PojoRecordReader}} requires exact model. In our case we'll need reader
that will allow dynamic model usage (the one where we don't know how many
columns it will have). For this purpose {{DynamicPojoRecordReader}} will be
used. Instead of exact model it will accept dynamic model represented by
{{List<LinkedHashMap<String, Object>> records}}, list of maps where key ->
column name, value -> column value. Common logic between {{PojoRecordReader}}
and {{DynamicPojoRecordReader}} will extracted in abstract parent class.
3. Currently when {{ConvertCountToDirectScan}} is applied in plan we see the
following:
{noformat}
Scan(groupscan=[org.apache.drill.exec.store.pojo.PojoRecordReader@60017daf[columns
= null, isStarQuery = false, isSkipQuery = false]])
{noformat}
User has no idea that column statistics was used to calculate the result, if
partition pruning took place etc, relates to DRILL-5357 and DRILL-3407.
Currently we use {{DirectGroupScan}} to hold our record reader. To include more
information we'll extend {{DirectGroupScan}} to {{MetadataDirectGroupScan}}
which will contain information about read files if any. Also
{{PojoRecordReader}} and {{DirectPojoRecordReader}} {{toString}} methods will
be overridden to show meaningful information to the user.
Example:
{noformat}
Scan(groupscan=[usedMetadata = true, files = [/tpch/nation.parquet],
DynamicPojoRecordReader{records=[{count0=25, count1=25, count2=25}]}])
{noformat}
> Count(dir0) on parquet returns 0 result
> ---------------------------------------
>
> Key: DRILL-4735
> URL: https://issues.apache.org/jira/browse/DRILL-4735
> Project: Apache Drill
> Issue Type: Bug
> Components: Query Planning & Optimization, Storage - Parquet
> Affects Versions: 1.0.0, 1.4.0, 1.6.0, 1.7.0
> Reporter: Krystal
> Assignee: Arina Ielchiieva
> Priority: Critical
>
> Selecting a count of dir0, dir1, etc against a parquet directory returns 0
> rows.
> select count(dir0) from `min_max_dir`;
> +---------+
> | EXPR$0 |
> +---------+
> | 0 |
> +---------+
> select count(dir1) from `min_max_dir`;
> +---------+
> | EXPR$0 |
> +---------+
> | 0 |
> +---------+
> If I put both dir0 and dir1 in the same select, it returns expected result:
> select count(dir0), count(dir1) from `min_max_dir`;
> +---------+---------+
> | EXPR$0 | EXPR$1 |
> +---------+---------+
> | 600 | 600 |
> +---------+---------+
> Here is the physical plan for count(dir0) query:
> {code}
> 00-00 Screen : rowType = RecordType(BIGINT EXPR$0): rowcount = 20.0,
> cumulative cost = {22.0 rows, 22.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id
> = 1346
> 00-01 Project(EXPR$0=[$0]) : rowType = RecordType(BIGINT EXPR$0):
> rowcount = 20.0, cumulative cost = {20.0 rows, 20.0 cpu, 0.0 io, 0.0 network,
> 0.0 memory}, id = 1345
> 00-02 Project(EXPR$0=[$0]) : rowType = RecordType(BIGINT EXPR$0):
> rowcount = 20.0, cumulative cost = {20.0 rows, 20.0 cpu, 0.0 io, 0.0 network,
> 0.0 memory}, id = 1344
> 00-03
> Scan(groupscan=[org.apache.drill.exec.store.pojo.PojoRecordReader@3da85d3b[columns
> = null, isStarQuery = false, isSkipQuery = false]]) : rowType =
> RecordType(BIGINT count): rowcount = 20.0, cumulative cost = {20.0 rows, 20.0
> cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 1343
> {code}
> Here is part of the explain plan for the count(dir0) and count(dir1) in the
> same select:
> {code}
> 00-00 Screen : rowType = RecordType(BIGINT EXPR$0, BIGINT EXPR$1):
> rowcount = 60.0, cumulative cost = {1206.0 rows, 15606.0 cpu, 0.0 io, 0.0
> network, 0.0 memory}, id = 1623
> 00-01 Project(EXPR$0=[$0], EXPR$1=[$1]) : rowType = RecordType(BIGINT
> EXPR$0, BIGINT EXPR$1): rowcount = 60.0, cumulative cost = {1200.0 rows,
> 15600.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 1622
> 00-02 StreamAgg(group=[{}], EXPR$0=[COUNT($0)], EXPR$1=[COUNT($1)]) :
> rowType = RecordType(BIGINT EXPR$0, BIGINT EXPR$1): rowcount = 60.0,
> cumulative cost = {1200.0 rows, 15600.0 cpu, 0.0 io, 0.0 network, 0.0
> memory}, id = 1621
> 00-03 Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath
> [path=maprfs:/drill/testdata/min_max_dir/1999/Apr/voter20.parquet/0_0_0.parquet],
> ReadEntryWithPath
> [path=maprfs:/drill/testdata/min_max_dir/1999/MAR/voter15.parquet/0_0_0.parquet],
> ReadEntryWithPath
> [path=maprfs:/drill/testdata/min_max_dir/1985/jan/voter5.parquet/0_0_0.parquet],
> ReadEntryWithPath
> [path=maprfs:/drill/testdata/min_max_dir/1985/apr/voter60.parquet/0_0_0.parquet],...,
> ReadEntryWithPath
> [path=maprfs:/drill/testdata/min_max_dir/2014/jul/voter35.parquet/0_0_0.parquet]],
> selectionRoot=maprfs:/drill/testdata/min_max_dir, numFiles=16,
> usedMetadataFile=false, columns=[`dir0`, `dir1`]]]) : rowType =
> RecordType(ANY dir0, ANY dir1): rowcount = 600.0, cumulative cost = {600.0
> rows, 1200.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 1620
> {code}
> Notice that in the first case,
> "org.apache.drill.exec.store.pojo.PojoRecordReader" is used.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
