Vitalii,
I made both the changes, it did not work and a full scan was issued as
shown in the plan below.
00-00 Screen : rowType = RecordType(INTEGER actor_id, VARCHAR(45)
first_name, VARCHAR(45) last_name, TIMESTAMP(3) last_update): rowcount
= 5.0, cumulative cost = {120.5 rows, 165.5 cpu, 0.0 io, 0.0 network,
0.0 memory}, id = 227
00-01 Project(actor_id=[$0], first_name=[$1], last_name=[$2],
last_update=[$3]) : rowType = RecordType(INTEGER actor_id, VARCHAR(45)
first_name, VARCHAR(45) last_name, TIMESTAMP(3) last_update): rowcount
= 5.0, cumulative cost = {120.0 rows, 165.0 cpu, 0.0 io, 0.0 network,
0.0 memory}, id = 226
00-02 SelectionVectorRemover : rowType = RecordType(INTEGER
actor_id, VARCHAR(45) first_name, VARCHAR(45) last_name, TIMESTAMP(3)
last_update): rowcount = 5.0, cumulative cost = {115.0 rows, 145.0
cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 225
00-03 Limit(fetch=[5]) : rowType = RecordType(INTEGER
actor_id, VARCHAR(45) first_name, VARCHAR(45) last_name, TIMESTAMP(3)
last_update): rowcount = 5.0, cumulative cost = {110.0 rows, 140.0
cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 224
00-04 Limit(fetch=[5]) : rowType = RecordType(INTEGER
actor_id, VARCHAR(45) first_name, VARCHAR(45) last_name, TIMESTAMP(3)
last_update): rowcount = 5.0, cumulative cost = {105.0 rows, 120.0
cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 223
00-05 Jdbc(sql=[SELECT * FROM "public"."actor" ]) :
rowType = RecordType(INTEGER actor_id, VARCHAR(45) first_name,
VARCHAR(45) last_name, TIMESTAMP(3) last_update): rowcount = 100.0,
cumulative cost = {100.0 rows, 100.0 cpu, 0.0 io, 0.0 network, 0.0
memory}, id = 164
Regards,
Rahul
On Fri, Oct 19, 2018 at 8:47 PM Rahul Raj <[email protected]> wrote:
> I will make the changes and update you.
>
> Regards,
> Rahul
>
> On Fri, Oct 19, 2018 at 1:05 AM Vitalii Diravka <[email protected]>
> wrote:
>
>> Rahul,
>>
>> Possibly *JdbcGroupScan* can be improved, for instance by overriding
>> *supportsLimitPushdown()* and *applyLimit()* methods,
>> *double rows *field can be updated by the limit value.
>>
>> I've performed the following query: select * from mysql.`testdb`.`table`
>> limit 2;
>> but the following one is passed to MySQL: SELECT * FROM `testdb`.`table`
>>
>> https://github.com/apache/drill/blob/master/contrib/storage-jdbc/src/main/java/org/apache/drill/exec/store/jdbc/JdbcRecordReader.java#L187
>> So it is definitely should be improved.
>>
>> *Note:* Changed mailing list to devs.
>>
>> On Sun, Oct 14, 2018 at 6:30 AM Rahul Raj <[email protected]> wrote:
>>
>> > Vitalii,
>> >
>> > Created documentation ticket DRILL-6794
>> >
>> > How do we proceed on extending the scan operators to support JDBC
>> plugins?
>> >
>> > Regards,
>> > Rahul
>> >
>> > On Sat, Oct 13, 2018 at 6:47 PM Vitalii Diravka <[email protected]>
>> > wrote:
>> >
>> > > To update the documentation, since that issues were solved by using
>> these
>> > > properties in connection URL:
>> > > defaultRowFetchSize=10000 [1]
>> > > defaultAutoCommit=false [2]
>> > > The full URL was there "url": "jdbc:postgresql://
>> > >
>> > >
>> >
>> myhost.mydomain.com/mydb?useCursorFetch=true&defaultAutoCommit=false&loggerLevel=TRACE&loggerFile=/tmp/jdbc.log&defaultRowFetchSize=10000
>> > > "
>> > >
>> > > If some issues are still present, it is also reasonable to create
>> tickets
>> > > to track them.
>> > >
>> > > [1]
>> > >
>> > >
>> >
>> https://mail-archives.apache.org/mod_mbox/drill-user/201808.mbox/%3CCADN0Fn9066hwvu_ZyDJ24tkAoJH5hqXoysCv83z7DdSSfjr-CQ%40mail.gmail.com%3E
>> > > [2]
>> > >
>> > >
>> >
>> https://mail-archives.apache.org/mod_mbox/drill-user/201808.mbox/%3C0d36e0e6e8dc1e77bbb67bbfde5f5296e290c075.camel%40omnicell.com%3E
>> > >
>> > > On Sat, Oct 13, 2018 at 3:56 PM Rahul Raj <[email protected]>
>> wrote:
>> > >
>> > > > Should I create tickets to track these issues or should I create a
>> > ticket
>> > > > to update the documentation?
>> > > >
>> > > > Rahul
>> > > >
>> > > > On Sat, Oct 13, 2018 at 6:16 PM Vitalii Diravka <[email protected]
>> >
>> > > > wrote:
>> > > >
>> > > > > 1. You are right, it means it is reasonable to extend this rule
>> for
>> > > > > applying on other Scan operators (or possibly to create the
>> separate
>> > > > one).
>> > > > > 2. There was a question about OOM issues in Drill + PostgreSQL,
>> > please
>> > > > take
>> > > > > a look [1].
>> > > > > Since you are trying to setup this configs, It will be good,
>> if
>> > you
>> > > > > create a Jira ticket to add this info to Drill docs [2]
>> > > > >
>> > > > > [1]
>> > > > >
>> > >
>> https://mail-archives.apache.org/mod_mbox/drill-user/201808.mbox/browser
>> > > > > [2] https://drill.apache.org/docs/rdbms-storage-plugin/
>> > > > >
>> > > > > On Sat, Oct 13, 2018 at 2:21 PM Rahul Raj <[email protected]>
>> > > wrote:
>> > > > >
>> > > > > > Regarding the heap out of error, it could be that the jdbc
>> driver
>> > is
>> > > > > > prefetching the entire record set to memory. I just had a look
>> at
>> > > > > > JdbcRecordReader, looks like by setting
>> > connection#autoCommit(false)
>> > > > and
>> > > > > a
>> > > > > > sufficient fetch size we could force the driver to stream data
>> as
>> > > > > required.
>> > > > > > This is how postgres driver works.
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://jdbc.postgresql.org/documentation/head/query.html#query-with-cursor
>> > > > > >
>> > > > > > We will have to see the behaviour of other drivers too.
>> > > > > >
>> > > > > > Let me know your thoughts here.
>> > > > > >
>> > > > > > Regards,
>> > > > > > Rahul
>> > > > > >
>> > > > > >
>> > > > > > On Sat, Oct 13, 2018 at 3:47 PM Rahul Raj <[email protected]
>> >
>> > > > wrote:
>> > > > > >
>> > > > > > > Hi Vitalii,
>> > > > > > >
>> > > > > > > There are two concrete implementations of the class -
>> > > > > > > DrillPushLimitToScanRule LIMIT_ON_SCAN and
>> > > > > > > DrillPushLimitToScanRule LIMIT_ON_PROJECT.
>> > > > > > > LIMIT_ON_SCAN has a comment mentioning "For now only applies
>> to
>> > > > > Parquet.
>> > > > > > > And pushdown only apply limit but not offset"
>> > > > > > >
>> > > > > > > Also I enabled debug mode and found LIMIT is not getting
>> pushed
>> > to
>> > > > the
>> > > > > > > query.
>> > > > > > > LimitPrel(fetch=[11]): rowcount = 11.0, cumulative cost =
>> > {83.0
>> > > > > rows,
>> > > > > > > 226.0 cpu, 0.0 io, 585728.0 network, 0.0 memory}, id = 261
>> > > > > > > UnionExchangePrel: rowcount = 11.0, cumulative cost =
>> {72.0
>> > > > rows,
>> > > > > > > 182.0 cpu, 0.0 io, 585728.0 network, 0.0 memory}, id = 259
>> > > > > > > LimitPrel(fetch=[11]): rowcount = 11.0, cumulative
>> cost =
>> > > > {61.0
>> > > > > > > rows, 94.0 cpu, 0.0 io, 0.0 network, 0.0 memory}, id = 257
>> > > > > > > JdbcPrel(sql=[SELECT * FROM
>> > "u_g001"."executioniteration"
>> > > > > WHERE
>> > > > > > > "id" > 360500000 ]): rowcount = 50.0, cumulative cost = {50.0
>> > rows,
>> > > > > 50.0
>> > > > > > cpu
>> > > > > > >
>> > > > > > > Regarding the second point, its the java heap getting filled
>> with
>> > > > jdbc
>> > > > > > > results. How do we address this?
>> > > > > > >
>> > > > > > > Regards,
>> > > > > > > Rahul
>> > > > > > >
>> > > > > > > On Fri, Oct 12, 2018 at 8:11 PM Vitalii Diravka <
>> > > [email protected]>
>> > > > > > > wrote:
>> > > > > > >
>> > > > > > >> Hi Rahul,
>> > > > > > >>
>> > > > > > >> Drill has *DrillPushLimitToScanRule* [1] rule, which should
>> do
>> > > this
>> > > > > > >> optimization, whether the GroupScan supports Limit Push Down.
>> > > > > > >> Also you can verify in debug mode whether this rule is fired.
>> > > > > > >> Possibly for some external DB (like MapR-DB) Drill should
>> have
>> > the
>> > > > > > >> separate
>> > > > > > >> class for this optimization [2].
>> > > > > > >>
>> > > > > > >> [1]
>> > > > > > >>
>> > > > > > >>
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillPushLimitToScanRule.java#L28
>> > > > > > >> [2]
>> > > > > > >>
>> > > > > > >>
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://github.com/apache/drill/pull/1466/files#diff-4819b70118487d81bc9c46a04b0eaaa3R37
>> > > > > > >>
>> > > > > > >> On Fri, Oct 12, 2018 at 3:19 PM Rahul Raj <
>> [email protected]
>> > >
>> > > > > wrote:
>> > > > > > >>
>> > > > > > >> > Hi,
>> > > > > > >> >
>> > > > > > >> > Drill does not push the LIMIT queries to external databases
>> > and
>> > > I
>> > > > > > >> assume it
>> > > > > > >> > could be more related to Calcite. This leads to out of
>> memory
>> > > > > > situations
>> > > > > > >> > while querying large table to view few records. Is there
>> > > > something
>> > > > > > that
>> > > > > > >> > could be improved here? One solutions would be to push
>> filters
>> > > > down
>> > > > > to
>> > > > > > >> the
>> > > > > > >> > DB and/or combined with some JDBC batch size limit to
>> flush a
>> > > part
>> > > > > as
>> > > > > > >> > parquet.
>> > > > > > >> >
>> > > > > > >> > Regards,
>> > > > > > >> > Rahul
>> > > > > > >> >
>> > > > > > >> > --
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