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From "Jinfeng Ni (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (DRILL-4378) CONVERT_FROM in View results in table scan of MapR-DB and perhaps HBASE
Date Tue, 09 Feb 2016 18:10:18 GMT

     [ https://issues.apache.org/jira/browse/DRILL-4378?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jinfeng Ni reassigned DRILL-4378:
---------------------------------

    Assignee: Jinfeng Ni

> CONVERT_FROM in View results in table scan of MapR-DB and perhaps HBASE
> -----------------------------------------------------------------------
>
>                 Key: DRILL-4378
>                 URL: https://issues.apache.org/jira/browse/DRILL-4378
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization, Storage - HBase
>    Affects Versions: 1.4.0
>            Reporter: John Omernik
>            Assignee: Jinfeng Ni
>
>  I created a view to avoid forcing users to write queries that always included the CONVERT_FROM
statements. (I am a huge advocate of making things easy for the the users and writing queries
with CONVERT_FROM statements isn't easy). 
> I ran a query the other day on one of these views and noticed that a query that took
30 seconds really shouldn't take 30 seconds.  What do I mean? well I wanted to get part of
a record by looking up the MapR-DB Row key (equiv. to HBASE row key)  That should be an instant
lookup.  Sure enough, when I tried it in the hbase shell that returns instantly.  So why did
Drill take 30 seconds?  I shot an email to Ted and Jim at MapR to ask this very question.
Ted suggested that I try the query without a view.  Sure enough, If I use the convert_from
in a direct query, it's an instant (sub second) return.  Thus it appears something in the
view is not allowing the query to short circuit the read.  
> Ted suggests I post here  (I am curious if anyone who has HBASE setup is seeing this
same issue with views) but also include the EXPLAIN plan.  Basically, using my very limited
ability to read EXPLAIN plans (If someone has a pointer to a blog post or docs on how to read
EXPLAIN I would love that!) it looks like in the view the startRow and stopRow in the hbaseScanSpec
are not set, seeming to cause a scan.  Is there any away to assist the planner when running
this through a view so that we can get the performance of the query without the view but with
the easy of use/readability of using the view?
> Thanks!!!
> John
> View Creation
> CREATE VIEW view_testpaste as 
> SELECT 
> CONVERT_FROM(row_key, 'UTF8') AS pasteid,
> CONVERT_FROM(pastes.pdata.lang, 'UTF8') AS lang,
> CONVERT_FROM(pastes.raw.paste, 'UTF8') AS paste
> FROM dfs.`pastes`.`/pastes` pastes;
> Select from view takes 32 seconds (seems to be a scan)
> > select paste from view_testpaste where pasteid = 'djHEHcPM'
> 1 row selected (32.302 seconds)
> Just a direct select returns very fast (0.486 seconds)
> > select CONVERT_FROM(pastes.raw.paste, 'UTF8') AS paste
> FROM dfs.`pastes`.`/pastes` pastes where 
> CONVERT_FROM(row_key, 'UTF8') = 'djHEHcPM';
> 1 row selected (0.486 seconds)
> EXPLAIN PLAN FOR select paste from view_testpaste where pasteid = 'djHEHcPM'
> +------+------+
> | text | json |
> +------+------+
> | 00-00    Screen
> 00-01      UnionExchange
> 01-01        Project(paste=[CONVERT_FROMUTF8($1)])
> 01-02          SelectionVectorRemover
> 01-03            Filter(condition=[=(CONVERT_FROMUTF8($0), 'djHEHcPM')])
> 01-04              Project(row_key=[$1], ITEM=[ITEM($0, 'paste')])
> 01-05                Scan(groupscan=[MapRDBGroupScan [HBaseScanSpec=HBaseScanSpec [tableName=maprfs:///data/pastebiner/pastes,
startRow=null, stopRow=null, filter=null], columns=[`row_key`, `raw`.`paste`]]])
>  | {
>   "head" : {
>     "version" : 1,
>     "generator" : {
>       "type" : "ExplainHandler",
>       "info" : ""
>     },
>     "type" : "APACHE_DRILL_PHYSICAL",
>     "options" : [ ],
>     "queue" : 0,
>     "resultMode" : "EXEC"
>   },
>   "graph" : [ {
>     "pop" : "maprdb-scan",
>     "@id" : 65541,
>     "userName" : "darkness",
>     "hbaseScanSpec" : {
>       "tableName" : "maprfs:///data/pastebiner/pastes",
>       "startRow" : "",
>       "stopRow" : "",
>       "serializedFilter" : null
>     },
>     "storage" : {
>       "type" : "file",
>       "enabled" : true,
>       "connection" : "maprfs:///",
>       "workspaces" : {
>         "root" : {
>           "location" : "/",
>           "writable" : false,
>           "defaultInputFormat" : null
>         },
>          "pastes" : {
>           "location" : "/data/pastebiner",
>           "writable" : true,
>           "defaultInputFormat" : null
>         },
>         "dev" : {
>           "location" : "/data/dev",
>           "writable" : true,
>           "defaultInputFormat" : null
>         },
>         "hive" : {
>           "location" : "/user/hive",
>           "writable" : true,
>           "defaultInputFormat" : null
>         },
>         "tmp" : {
>           "location" : "/tmp",
>           "writable" : true,
>           "defaultInputFormat" : null
>         }
>       },
>       "formats" : {
>         "psv" : {
>           "type" : "text",
>           "extensions" : [ "tbl" ],
>           "delimiter" : "|"
>         },
>         "csv" : {
>           "type" : "text",
>           "extensions" : [ "csv" ],
>           "escape" : "`",
>           "delimiter" : ","
>         },
>         "tsv" : {
>           "type" : "text",
>           "extensions" : [ "tsv" ],
>           "delimiter" : "\t"
>         },
>         "parquet" : {
>           "type" : "parquet"
>         },
>         "json" : {
>           "type" : "json"
>         },
>         "maprdb" : {
>           "type" : "maprdb"
>         }
>       }
>     },
>     "columns" : [ "`row_key`", "`raw`.`paste`" ],
>     "cost" : 573950.0
>   }, {
>     "pop" : "project",
>     "@id" : 65540,
>     "exprs" : [ {
>       "ref" : "`row_key`",
>       "expr" : "`row_key`"
>     }, {
>       "ref" : "`ITEM`",
>       "expr" : "`raw`.`paste`"
>     } ],
>     "child" : 65541,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 573950.0
>   }, {
>     "pop" : "filter",
>     "@id" : 65539,
>     "child" : 65540,
>     "expr" : "equal(convert_fromutf8(`row_key`) , 'djHEHcPM') ",
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 86092.5
>   }, {
>     "pop" : "selection-vector-remover",
>     "@id" : 65538,
>     "child" : 65539,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 86092.5
>   }, {
>     "pop" : "project",
>     "@id" : 65537,
>     "exprs" : [ {
>       "ref" : "`paste`",
>       "expr" : "convert_fromutf8(`ITEM`) "
>     } ],
>     "child" : 65538,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 86092.5
>   }, {
>     "pop" : "union-exchange",
>     "@id" : 1,
>     "child" : 65537,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 86092.5
>   }, {
>     "pop" : "screen",
>     "@id" : 0,
>     "child" : 1,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 86092.5
>   } ]
> } |
> +------+------+
> 1 row selected (0.42 seconds)
> EXPLAIN PLAN FOR select CONVERT_FROM(pastes.raw.paste, 'UTF8') AS paste
> FROM dfs.`pastes`.`/pastes` pastes where 
> CONVERT_FROM(row_key, 'UTF8') = 'djHEHcPM';
> +------+------+
> | text | json |
> +------+------+
> | 00-00    Screen
> 00-01      Project(paste=[CONVERT_FROMUTF8($1)])
> 00-02        Project(row_key=[$1], ITEM=[ITEM($0, 'paste')])
> 00-03          Scan(groupscan=[MapRDBGroupScan [HBaseScanSpec=HBaseScanSpec [tableName=maprfs:///data/pastebiner/pastes,
startRow=djHEHcPM, stopRow=djHEHcPM\x00, filter=RowFilter (EQUAL, djHEHcPM)], columns=[`row_key`,
`raw`.`paste`]]])
>  | {
>   "head" : {
>     "version" : 1,
>     "generator" : {
>       "type" : "ExplainHandler",
>       "info" : ""
>     },
>     "type" : "APACHE_DRILL_PHYSICAL",
>     "options" : [ ],
>     "queue" : 0,
>     "resultMode" : "EXEC"
>   },
>   "graph" : [ {
>     "pop" : "maprdb-scan",
>     "@id" : 3,
>     "userName" : "darkness",
>     "hbaseScanSpec" : {
>       "tableName" : "maprfs:///data/pastebiner/pastes",
>       "startRow" : "ZGpIRUhjUE0=",
>       "stopRow" : "ZGpIRUhjUE0A",
>       "serializedFilter" : "CihvcmcuYXBhY2hlLmhhZG9vcC5oYmFzZS5maWx0ZXIuUm93RmlsdGVyEkUKQwgCEj8KL29yZy5hcGFjaGUuaGFkb29wLmhiYXNlLmZpbHRlci5CaW5hcnlDb21wYXJhdG9yEgwKCgoIZGpIRUhjUE0="
>     },
>     "storage" : {
>       "type" : "file",
>       "enabled" : true,
>       "connection" : "maprfs:///",
>       "workspaces" : {
>         "root" : {
>           "location" : "/",
>           "writable" : false,
>           "defaultInputFormat" : null
>         },
>         "pastes" : {
>           "location" : "/data/pastebiner",
>           "writable" : true,
>           "defaultInputFormat" : null
>         },
>         "dev" : {
>           "location" : "/data/dev",
>           "writable" : true,
>           "defaultInputFormat" : null
>         },
>         "hive" : {
>           "location" : "/user/hive",
>           "writable" : true,
>           "defaultInputFormat" : null
>         },
>         "tmp" : {
>           "location" : "/tmp",
>           "writable" : true,
>           "defaultInputFormat" : null
>         }
>       },
>       "formats" : {
>         "psv" : {
>           "type" : "text",
>           "extensions" : [ "tbl" ],
>           "delimiter" : "|"
>         },
>         "csv" : {
>           "type" : "text",
>           "extensions" : [ "csv" ],
>           "escape" : "`",
>           "delimiter" : ","
>         },
>         "tsv" : {
>           "type" : "text",
>           "extensions" : [ "tsv" ],
>           "delimiter" : "\t"
>         },
>         "parquet" : {
>           "type" : "parquet"
>         },
>         "json" : {
>           "type" : "json"
>         },
>         "maprdb" : {
>           "type" : "maprdb"
>         }
>       }
>     },
>     "columns" : [ "`row_key`", "`raw`.`paste`" ],
>     "cost" : 286975.0
>   }, {
>     "pop" : "project",
>     "@id" : 2,
>     "exprs" : [ {
>       "ref" : "`row_key`",
>       "expr" : "`row_key`"
>     }, {
>       "ref" : "`ITEM`",
>       "expr" : "`raw`.`paste`"
>     } ],
>     "child" : 3,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 286975.0
>   }, {
>     "pop" : "project",
>     "@id" : 1,
>     "exprs" : [ {
>       "ref" : "`paste`",
>       "expr" : "convert_fromutf8(`ITEM`) "
>     } ],
>     "child" : 2,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 286975.0
>   }, {
>     "pop" : "screen",
>     "@id" : 0,
>     "child" : 1,
>     "initialAllocation" : 1000000,
>     "maxAllocation" : 10000000000,
>     "cost" : 286975.0
>   } ]
> } |



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