Oops, missed the "not" in one of my sentences. The corrected sentence should be:
You can tell that's the case because in the case of the view query, the explain plan has a Filter operation, whereas in the case of the non-view query you do NOT. -- Zelaine On Sun, Feb 7, 2016 at 11:09 AM, Zelaine Fong <[email protected]> wrote: > It looks like in the case of the non-view query, the WHERE clause is being > pushed down to MapR-DB. The pushdown isn't happening in the case of the > view. You can tell that's the case because in the case of the view query, > the explain plan has a Filter operation, whereas in the case of the > non-view query you do. As you noted, in the case of the non-view, the Scan > has a startRow/stopRow/filter, which corresponds to the pushdown of the > filter. > > I'm wondering if the problem is related to the CONVERT_FROM() in the WHERE > clause, or if all filters on views aren't being pushed down? > > -- Zelaine > > On Sat, Feb 6, 2016 at 2:02 PM, John Omernik <[email protected]> wrote: > >> Hey all, I was running some queries on a MapR-DB Table I have. 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 >> } ] >> } | >> > >
