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From Yingyi Bu <buyin...@gmail.com>
Subject Re: [jira] [Commented] (ASTERIXDB-1249) Self index join chooses wrong probe/index branch
Date Fri, 08 Jan 2016 17:08:07 GMT
In left-outer hash join, if the the probe branch is locally clustered (or
sorted) by a column superset of the join key,
the output will still be locally clustered.
Inner hash join couldn't maintain that because of the "role reversal"
optimization in the runtime.

Best,
Yingyi

On Thu, Jan 7, 2016 at 10:07 PM, Taewoo Kim <wangsaeu@gmail.com> wrote:

> Interesting. Can you be more specific?
>
> Best,
> Taewoo
>
> On Thu, Jan 7, 2016 at 6:36 PM, Yingyi Bu <buyingyi@gmail.com> wrote:
>
> > Sorry, to be more precise:
> > Left-outer hash join cannot preserve all local data properties for its
> > probe branch (because spilling can happen) but can preserve (or
> downgrade)
> > some when certain conditions meet.
> >
> > On Thu, Jan 7, 2016 at 6:28 PM, Yingyi Bu <buyingyi@gmail.com> wrote:
> >
> > > In the logical/physical query plan, I think it is statically
> determined.
> > > However, that doesn't mean the execution is faithful to that
> probe/build
> > > decision because we have the "role reversal" optimization for inner
> hash
> > > joins:-)
> > > (That's also why our inner hash join cannot maintain any local data
> > > property from its probe branch, but left-outer hash can preserve that.)
> > >
> > > Best,
> > > Yingyi
> > >
> > >
> > > On Thu, Jan 7, 2016 at 5:34 PM, Mike Carey <dtabass@gmail.com> wrote:
> > >
> > >> Also, do we (separately want to make sure that our hash join behavior
> is
> > >> comparable - i.e., that the initial build/probe decision is statically
> > >> determined from the query?  (I think we do want that, and I think it
> is
> > in
> > >> fact that way - but I'm not 100% sure, as its been awhile since that
> was
> > >> discussed, and it's not in-cache for me. :-))
> > >>
> > >>
> > >> On 1/7/16 3:22 PM, Taewoo Kim wrote:
> > >>
> > >>> Thanks Yingyi. Yes. If there is an equality condition and if we can't
> > >>> transform a join into an index-nested loop join, then a hybrid hash
> > join
> > >>> will be used.
> > >>>
> > >>> Best,
> > >>> Taewoo
> > >>>
> > >>> On Thu, Jan 7, 2016 at 3:14 PM, Yingyi Bu <buyingyi@gmail.com>
> wrote:
> > >>>
> > >>> +1!
> > >>>>
> > >>>>> 3. We only try to use applicable indexes from the inner branch.
So,
> > if
> > >>>>>> there are no applicable indexes from the inner branch,
we abort
> > >>>>>> transforming a join into an index-nested-loop join.
> > >>>>>>
> > >>>>> "index-nested-loop join" -> "hybrid hash join"?
> > >>>>
> > >>>> Thanks!
> > >>>>
> > >>>> Yingyi
> > >>>>
> > >>>>
> > >>>>
> > >>>> On Thu, Jan 7, 2016 at 3:01 PM, Taewoo Kim <wangsaeu@gmail.com>
> > wrote:
> > >>>>
> > >>>> Hello dev,
> > >>>>>
> > >>>>> Regarding this issue (ASTERIXDB-1249), I would like to make
an
> > >>>>> index-join
> > >>>>> hint clarification. Let's start with an example query other
than a
> > >>>>> self-join query in this issue.
> > >>>>>
> > >>>>> for $c in dataset('Customers')
> > >>>>>
> > >>>>> for $o in dataset('Orders')
> > >>>>>
> > >>>>> where $c.cid /*+ indexnl */ = $o.cid
> > >>>>>
> > >>>>> order by $c.cid, $o.oid
> > >>>>>
> > >>>>> return {"cid":$c.cid, "oid": $o.oid}
> > >>>>>
> > >>>>> Right now, in the master branch, the first dataset (e.g.,
> Customers)
> > >>>>> becomes the outer branch and the second dataset (e.g., Orders)
> > becomes
> > >>>>>
> > >>>> the
> > >>>>
> > >>>>> inner branch. And, when the optimizer tries to honor the given
> > indexnl
> > >>>>>
> > >>>> hint
> > >>>>
> > >>>>> (transforming a join into an index-nested-loop join), if there
are
> > >>>>> applicable indexes from the inner branch (e.g., Orders), then
it is
> > >>>>> going
> > >>>>> to use one of those indexes. If there are no applicable indexes
> from
> > >>>>> the
> > >>>>> inner branch, it tries to use indexes from the outer branch
(e.g.,
> > >>>>> Customers). We are going to change the last part; we will not
use
> > >>>>> indexes
> > >>>>> from the outer branch. So, the following are refined rules
for
> > >>>>>
> > >>>> transforming
> > >>>>
> > >>>>> a join into an index-nested-loop join.
> > >>>>>
> > >>>>> 1. The first dataset in a join (the first parameter of the
given
> > join)
> > >>>>> becomes the outer branch.
> > >>>>> 2. The second dataset in a join (the second parameter of the
given
> > >>>>> join)
> > >>>>> becomes the inner branch.
> > >>>>> 3. We only try to use applicable indexes from the inner branch.
So,
> > if
> > >>>>> there are no applicable indexes from the inner branch, we abort
> > >>>>> transforming a join into an index-nested-loop join.
> > >>>>> 4. Variable order in the given join predicate is not important.
It
> > can
> > >>>>> be
> > >>>>> either outer.fieldA = inner.fieldB or inner.fieldB = outer.fieldA.
> > >>>>>
> > >>>>> So, for the left-outer join and inner join altogether, the
left
> > subtree
> > >>>>>
> > >>>> is
> > >>>>
> > >>>>> the probing side and the right subtree is the index side. So,
this
> > can
> > >>>>> be
> > >>>>> applied to the self-join case, too just like the following
query in
> > >>>>> this
> > >>>>> issue. In the following query, $t1 becomes the outer and $t2
> becomes
> > >>>>> the
> > >>>>> inner.
> > >>>>>
> > >>>>> for $t1 in dataset('TweetMessages')
> > >>>>>
> > >>>>> for $t2 in dataset('TweetMessages')
> > >>>>>
> > >>>>> let $c := $t1.countA + 20
> > >>>>>
> > >>>>> where $c /* +indexnl */= $t2.countB
> > >>>>>
> > >>>>> order by $t2.tweetid
> > >>>>>
> > >>>>> return {"tweetid2": $t2.tweetid, "count2":$t2.countB};
> > >>>>>
> > >>>>> Thank you. Any opinion would be appreciated before I finalize
this
> > fix.
> > >>>>>
> > >>>>> Best,
> > >>>>> Taewoo
> > >>>>>
> > >>>>> ---------- Forwarded message ----------
> > >>>>> From: Yingyi Bu (JIRA) <jira@apache.org>
> > >>>>> Date: Wed, Jan 6, 2016 at 10:23 AM
> > >>>>> Subject: [jira] [Commented] (ASTERIXDB-1249) Self index join
> chooses
> > >>>>>
> > >>>> wrong
> > >>>>
> > >>>>> probe/index branch
> > >>>>> To: notifications@asterixdb.incubator.apache.org
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>>      [
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>
> >
> https://issues.apache.org/jira/browse/ASTERIXDB-1249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15085992#comment-15085992
> > >>>>
> > >>>>> ]
> > >>>>>
> > >>>>> Yingyi Bu commented on ASTERIXDB-1249:
> > >>>>> --------------------------------------
> > >>>>>
> > >>>>> That's right. Basically in AcessMethod implementations, e.g.:
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>
> >
> https://github.com/apache/incubator-asterixdb/blob/master/asterix-algebra/src/main/java/org/apache/asterix/optimizer/rules/am/RTreeAccessMethod.java#L124
> > >>>>
> > >>>>> Choosing probe/index branch is only based on dataset names,
instead
> > of
> > >>>>> being based on the join condition.
> > >>>>>
> > >>>>> Self index join chooses wrong probe/index branch
> > >>>>>> ------------------------------------------------
> > >>>>>>
> > >>>>>>                  Key: ASTERIXDB-1249
> > >>>>>>                  URL:
> > >>>>>>
> > >>>>> https://issues.apache.org/jira/browse/ASTERIXDB-1249
> > >>>>>
> > >>>>>>              Project: Apache AsterixDB
> > >>>>>>           Issue Type: Bug
> > >>>>>>           Components: Optimizer
> > >>>>>>             Reporter: Yingyi Bu
> > >>>>>>             Assignee: Taewoo Kim
> > >>>>>>
> > >>>>>> DDLs:
> > >>>>>> {noformat}
> > >>>>>> drop dataverse test if exists;
> > >>>>>> create dataverse test;
> > >>>>>> use dataverse test;
> > >>>>>> create type TwitterUserType as closed {
> > >>>>>>      screen-name: string,
> > >>>>>>      lang: string,
> > >>>>>>      friends-count: int64,
> > >>>>>>      statuses-count: int64,
> > >>>>>>      name: string,
> > >>>>>>      followers-count: int64
> > >>>>>> }
> > >>>>>> create type TweetMessageType as closed {
> > >>>>>>      tweetid: int64,
> > >>>>>>          user: TwitterUserType,
> > >>>>>>          sender-location: point,
> > >>>>>>      send-time: datetime,
> > >>>>>>          referred-topics: {{ string }},
> > >>>>>>      message-text: string,
> > >>>>>>      countA: int64,
> > >>>>>>      countB: int64
> > >>>>>> }
> > >>>>>> create dataset TweetMessages(TweetMessageType)
> > >>>>>> primary key tweetid;
> > >>>>>> create index twmSndLocIx on TweetMessages(sender-location)
type
> > rtree;
> > >>>>>> create index msgCountAIx on TweetMessages(countA) type
btree;
> > >>>>>> create index msgCountBIx on TweetMessages(countB) type
btree;
> > >>>>>> create index msgTextIx on TweetMessages(message-text) type
> keyword;
> > >>>>>> {noformat}
> > >>>>>> Query:
> > >>>>>> {noformat}
> > >>>>>> for $t1 in dataset('TweetMessages')
> > >>>>>> for $t2 in dataset('TweetMessages')
> > >>>>>> let $n :=  create-circle($t1.sender-location, 0.5)
> > >>>>>> where spatial-intersect($t2.sender-location, $n)
> > >>>>>> order by $t2.tweetid
> > >>>>>> return {"tweetid2":$t2.tweetid, "loc2":$t2.sender-location};
> > >>>>>> {noformat}
> > >>>>>> Optimized plan:
> > >>>>>> {noformat}
> > >>>>>> distribute result [%0->$$10]
> > >>>>>> -- DISTRIBUTE_RESULT  |PARTITIONED|
> > >>>>>>    exchange
> > >>>>>>    -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
> > >>>>>>      project ([$$10])
> > >>>>>>      -- STREAM_PROJECT  |PARTITIONED|
> > >>>>>>        assign [$$10] <- [function-call:
> > >>>>>>
> > >>>>> asterix:closed-record-constructor,
> > >>>>
> > >>>>> Args:[AString: {tweetid2}, %0->$$15, AString: {loc2}, %0->$$13]]
> > >>>>>
> > >>>>>>        -- ASSIGN  |PARTITIONED|
> > >>>>>>          exchange
> > >>>>>>          -- SORT_MERGE_EXCHANGE [$$15(ASC) ]  |PARTITIONED|
> > >>>>>>            order (ASC, %0->$$15)
> > >>>>>>            -- STABLE_SORT [$$15(ASC)]  |PARTITIONED|
> > >>>>>>              exchange
> > >>>>>>              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
> > >>>>>>                project ([$$13, $$15])
> > >>>>>>                -- STREAM_PROJECT  |PARTITIONED|
> > >>>>>>                  select (function-call: asterix:spatial-intersect,
> > >>>>>>
> > >>>>> Args:[%0->$$13, function-call: asterix:create-circle,
> > >>>>>
> > >>>> Args:[function-call:
> > >>>>
> > >>>>> asterix:field-access-by-index, Args:[%0->$$0, AInt32: {2}],
> ADouble:
> > >>>>> {0.5}]])
> > >>>>>
> > >>>>>>                  -- STREAM_SELECT  |PARTITIONED|
> > >>>>>>                    project ([$$0, $$13, $$15])
> > >>>>>>                    -- STREAM_PROJECT  |PARTITIONED|
> > >>>>>>                      exchange
> > >>>>>>                      -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
> > >>>>>>                        unnest-map [$$14, $$0] <- function-call:
> > >>>>>>
> > >>>>> asterix:index-search, Args:[AString: {TweetMessages}, AInt32:
{0},
> > >>>>>
> > >>>> AString:
> > >>>>
> > >>>>> {test}, AString: {TweetMessages}, ABoolean: {true}, ABoolean:
> > {false},
> > >>>>> ABoolean: {false}, AInt32: {1}, %0->$$27, AInt32: {1}, %0->$$27,
> > TRUE,
> > >>>>> TRUE, TRUE]
> > >>>>>
> > >>>>>>                        -- BTREE_SEARCH  |PARTITIONED|
> > >>>>>>                          exchange
> > >>>>>>                          -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
> > >>>>>>                            order (ASC, %0->$$27)
> > >>>>>>                            -- STABLE_SORT [$$27(ASC)]
> |PARTITIONED|
> > >>>>>>                              exchange
> > >>>>>>                              -- ONE_TO_ONE_EXCHANGE  |PARTITIONED|
> > >>>>>>                                project ([$$27, $$13, $$15])
> > >>>>>>                                -- STREAM_PROJECT  |PARTITIONED|
> > >>>>>>                                  exchange
> > >>>>>>                                  -- ONE_TO_ONE_EXCHANGE
> > |PARTITIONED|
> > >>>>>>                                    unnest-map [$$23, $$24,
$$25,
> > $$26,
> > >>>>>>
> > >>>>> $$27] <- function-call: asterix:index-search, Args:[AString:
> > >>>>>
> > >>>> {twmSndLocIx},
> > >>>>
> > >>>>> AInt32: {1}, AString: {test}, AString: {TweetMessages}, ABoolean:
> > >>>>> {true},
> > >>>>> ABoolean: {false}, ABoolean: {true}, AInt32: {4}, %0->$$19,
> %0->$$20,
> > >>>>> %0->$$21, %0->$$22]
> > >>>>>
> > >>>>>>                                    -- RTREE_SEARCH  |PARTITIONED|
> > >>>>>>                                      exchange
> > >>>>>>                                      -- BROADCAST_EXCHANGE
> > >>>>>>
> > >>>>> |PARTITIONED|
> > >>>>
> > >>>>>                                        assign [$$19, $$20,
$$21,
> > $$22]
> > >>>>>>
> > >>>>> <-
> > >>>>
> > >>>>> [function-call: asterix:create-mbr, Args:[%0->$$13, AInt32:
{2},
> > >>>>> AInt32:
> > >>>>> {0}], function-call: asterix:create-mbr, Args:[%0->$$13,
AInt32:
> {2},
> > >>>>> AInt32: {1}], function-call: asterix:create-mbr, Args:[%0->$$13,
> > >>>>> AInt32:
> > >>>>> {2}, AInt32: {2}], function-call: asterix:create-mbr,
> Args:[%0->$$13,
> > >>>>> AInt32: {2}, AInt32: {3}]]
> > >>>>>
> > >>>>>>                                        -- ASSIGN  |PARTITIONED|
> > >>>>>>                                          project ([$$13,
$$15])
> > >>>>>>                                          -- STREAM_PROJECT
> > >>>>>>
> > >>>>> |PARTITIONED|
> > >>>>
> > >>>>>                                            assign [$$13] <-
> > >>>>>>
> > >>>>> [function-call: asterix:field-access-by-index, Args:[%0->$$1,
> AInt32:
> > >>>>>
> > >>>> {2}]]
> > >>>>
> > >>>>>                                            -- ASSIGN  |PARTITIONED|
> > >>>>>>                                              exchange
> > >>>>>>                                              --
> ONE_TO_ONE_EXCHANGE
> > >>>>>>
> > >>>>> |PARTITIONED|
> > >>>>>
> > >>>>>>                                                data-scan
> []<-[$$15,
> > >>>>>> $$1]
> > >>>>>>
> > >>>>> <- test:TweetMessages
> > >>>>>
> > >>>>>>                                                -- DATASOURCE_SCAN
> > >>>>>>
> > >>>>> |PARTITIONED|
> > >>>>>
> > >>>>>>                                                  exchange
> > >>>>>>                                                  --
> > >>>>>> ONE_TO_ONE_EXCHANGE
> > >>>>>>
> > >>>>> |PARTITIONED|
> > >>>>>
> > >>>>>>
> > empty-tuple-source
> > >>>>>>                                                    --
> > >>>>>> EMPTY_TUPLE_SOURCE
> > >>>>>>
> > >>>>> |PARTITIONED|
> > >>>>>
> > >>>>>> {noformat}
> > >>>>>> The optimized plan is incorrect --- the index search doesn't
use
> the
> > >>>>>>
> > >>>>> right join condition and hence the result is different from
> expected.
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> --
> > >>>>> This message was sent by Atlassian JIRA
> > >>>>> (v6.3.4#6332)
> > >>>>>
> > >>>>>
> > >>
> > >
> >
>

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