Re: window function vs. PARTITION RANGE ITERATOR
Date: Mon, 8 Oct 2018 13:52:49 +0100
Message-ID: <CACj1VR6iu-eCqLn0Mydm6cyK4PyC7D05o9A9x8Ywviq3yFTjQQ_at_mail.gmail.com>
You can only push the filter if it is used in the partition by clause.
Since your partition by group uses trunc(snap_time), you could also filter
on that but this doesn't help much as your table partitioning is done
against snap_time.
But, it seems to me like it should be easy enough to just partition by
trunc(snap_time) using virtual columns:
CREATE TABLE "H3G_SYSSTAT_METRICS"
)
with raw_data as (select /*+ NO_INDEX( h ) */ h.*, h.snap_time snap_time2
from H3G_SYSSTAT_METRICS h
OVER (PARTITION BY STAT_NAME, instance_name,database_id, server,
trunc_SNAP_TIME ORDER BY SNAP_TIME desc) as rr -- altered partition by
from raw_data)
("STAT_NAME" VARCHAR2(64 BYTE) NOT NULL ENABLE,
"SNAP_TIME" DATE NOT NULL ENABLE,
"DATABASE_ID" NUMBER NOT NULL ENABLE,
"INSTANCE_NAME" VARCHAR2(64 BYTE) NOT NULL ENABLE,
"SERVER" VARCHAR2(64 BYTE) NOT NULL ENABLE,
"STARTUP_TIME" DATE NOT NULL ENABLE,
"VALUE" NUMBER NOT NULL ENABLE
,trunc_snap_time date as (trunc(snap_time)) -- virtual column
TABLESPACE "USERS"
PARTITION BY LIST ("STAT_NAME")
SUBPARTITION BY RANGE (trunc_snap_time) -- altered column
(PARTITION "P2" VALUES ('CPU used by this session')
TABLESPACE "USERS"
COMPRESS BASIC
( SUBPARTITION "P2_000000" VALUES LESS THAN (TO_DATE(' 2016-01-01
00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
TABLESPACE "USERS"
COMPRESS BASIC ,
SUBPARTITION "P2_201600" VALUES LESS THAN (TO_DATE(' 2017-01-01
00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
TABLESPACE "USERS"
))
/
where 1=1
-- and snap_time >= sysdate - 3
), better as (
select stat_name, instance_name, database_id, server, trunc_SNAP_TIME
trunc_snap, snap_time, value, rank() -- altered trunc_snap
select
-- BX012
*
from better
where rr=1
and stat_name='physical read bytes'
and snap_time >= sysdate - 3
and trunc_snap >= trunc(sysdate) - 3 -- extra filter
;
Plan hash value: 1756919075
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | ------------------------------------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1 | 159 | 3 (34)| 00:00:01 | | | |* 1 | VIEW | | 1 | 159 | 3 (34)| 00:00:01 | | | |* 2 | WINDOW SORT PUSHED RANK | | 1 | 146 | 3 (34)| 00:00:01 | | | | 3 | PARTITION LIST EMPTY | | 1 | 146 | 2 (0)| 00:00:01 |INVALID|INVALID| | 4 | PARTITION RANGE ITERATOR| | 1 | 146 | 2 (0)| 00:00:01 | KEY | 2 | |* 5 | TABLE ACCESS FULL | H3G_SYSSTAT_METRICS | 1 | 146 | 2 (0)| 00:00:01 |INVALID|INVALID| -------------------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
1 - filter("RR"=1 AND "SNAP_TIME">=SYSDATE_at_!-3)
2 - filter(RANK() OVER ( PARTITION BY
"H"."STAT_NAME","H"."INSTANCE_NAME","H"."DATABASE_ID","H"."SERVER"
,"H"."TRUNC_SNAP_TIME" ORDER BY
INTERNAL_FUNCTION("SNAP_TIME") DESC )<=1)
5 - filter("H"."STAT_NAME"='physical read bytes' AND
"H"."TRUNC_SNAP_TIME">=TRUNC(SYSDATE_at_!)-3)
Note
- dynamic statistics used: dynamic sampling (level=2)
Hope this helps
Andy
On Mon, 8 Oct 2018 at 13:31, l.flatz_at_bluewin.ch <l.flatz_at_bluewin.ch> wrote:
> Hi Martin,
>
> it seems that the snap_time condition can not be pushed down into the
> better view.
> Probably the window function is preventing that. You might want to
> experiment based on that. (
> https://asktom.oracle.com/pls/apex/f?p=100:11:0::NO::P11_QUESTION_ID:3469884600671
> ).
> It should be possible to push a condition based on column included in the
> partition clause of wndow function.
> You use trunc(SNAP_TIME) there.
> Try using trunc(SNAP_TIME) everywhere or just snap_time plain.
>
> Regards
>
> Lothar
>
> ----Ursprüngliche Nachricht----
> Von : martin.a.berger_at_gmail.com
> Datum : 08/10/2018 - 13:58 (GMT)
> An : oracle-l_at_freelists.org
> Betreff : window function vs. PARTITION RANGE ITERATOR
>
> Dear list,
>
> I have a DB (12.1.0.2 - Jan 2018 BP - 2 node RAC)
> with a table "SYSSTAT_METRICS" which holds regular snapshots of sysstat
> metrics of many DBs.
> the table has
> columns STAT_NAME, SNAP_TIME, DATABASE_ID, INSTANCE_NAME, SERVER, STARTUP_TIME, VALUE.
> The table is partitioned by LIST ("STAT_NAME") and subpartitioned BY
> RANGE ("SNAP_TIME")
> The SNAP_TIME subpartitions are monthly partitions. (details at the end of
> this email)
>
> I want to have a View query which gives daily last snap_time & value for
> every stat, db, instance, server. In this view I'd like to efficient filter
> by STAT_NAME (most only 1 statistic of interest) and SNAP_TIME (e.g. last
> month or last 3 month - or December-2017).
>
> I have a select like this:
> with raw_data as (select /*+ NO_INDEX( h ) */ h.*, h.snap_time snap_time2
> from sysstat_metrics h
> where 1=1
> * and snap_time >= sysdate - 3*
> ), better as (
> select stat_name, instance_name, database_id, server, trunc(snap_time)
> trunc_snap, snap_time, value, rank()
> OVER (PARTITION BY STAT_NAME, instance_name,database_id, server,
> trunc(SNAP_TIME) ORDER BY SNAP_TIME desc) as rr
> from raw_data)
> select
> -- BX011
> *
> from better
> where rr=1
> and stat_name='physical read bytes'
> -- and snap_time >= sysdate - 3
> ;
>
> The Plan shows
> Plan hash value: 1030407344
>
>
> ---------------------------------------------------------------------------------------------------------------------------------------------
> | Id | Operation | Name | Starts | E-Rows |
> A-Rows | A-Time | Buffers | Reads | OMem | 1Mem | Used-Mem |
>
> ---------------------------------------------------------------------------------------------------------------------------------------------
> | 0 | SELECT STATEMENT | | 1 | |
> 2868 |00:00:00.21 | 1921 | 11 | | | |
> |* 1 | VIEW | | 1 | 3 |
> 2868 |00:00:00.21 | 1921 | 11 | | | |
> |* 2 | WINDOW SORT PUSHED RANK | | 1 | 3 |
> 2868 |00:00:00.21 | 1921 | 11 | 6715K| 1041K| 5968K (0)|
> | 3 | PARTITION LIST SINGLE | | 1 | 3 |
> 51612 |00:00:00.04 | 1921 | 11 | | | |
> | 4 | *PARTITION RANGE ITERATOR*| | 1 | 3
> | 51612 |00:00:00.04 | 1921 | 11 | | | |
> |* 5 | TABLE ACCESS FULL | SYSSTAT_METRICS | 4 | 3 |
> 51612 |00:00:00.03 | 1921 | 11 | | | |
>
> ---------------------------------------------------------------------------------------------------------------------------------------------
>
> Predicate Information (identified by operation id):
> ---------------------------------------------------
>
> 1 - filter("RR"=1)
> 2 - filter(RANK() OVER ( PARTITION BY
> "H"."STAT_NAME","H"."INSTANCE_NAME","H"."DATABASE_ID","H"."SERVER",TRUNC(INTERNAL_FUNCTION("H"."
> SNAP_TIME")) ORDER BY INTERNAL_FUNCTION("SNAP_TIME") DESC
> )<=1)
> *5 - filter("SNAP_TIME">=SYSDATE_at_!-3)*
>
> and it's nice as there is a PARTITION RANGE ITERATOR (so not all range
> partitions are used at all) and the Filter is quite early.
>
> But if I change the same filter down to the "outer" subquery:
>
> with raw_data as (select /*+ NO_INDEX( h ) */ h.*, h.snap_time snap_time2
> from sysstat_metrics h
> where 1=1
> *--* and snap_time >= sysdate - 3
> ), better as (
> select stat_name, instance_name, database_id, server, trunc(snap_time)
> trunc_snap, snap_time, value, rank()
> OVER (PARTITION BY STAT_NAME, instance_name,database_id, server,
> trunc(SNAP_TIME) ORDER BY SNAP_TIME desc) as rr
> from raw_data)
> select
> -- BX012
> *
> from better
> where rr=1
> and stat_name='physical read bytes'
> * and snap_time >= sysdate - 3*
> ;
>
> The plan changes to ugly
> Plan hash value: 2132163184
>
>
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
> | Id | Operation | Name | Starts | E-Rows |
> A-Rows | A-Time | Buffers | Reads | Writes | OMem | 1Mem | Used-Mem
> | Used-Tmp|
>
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
> | 0 | SELECT STATEMENT | | 1 | |
> 2868 |00:00:34.24 | 100K| 38026 | 32252 | | |
> | |
> |* *1* | VIEW | | 1 | 9387K|
> 2868 |00:00:34.24 | 100K| 38026 | 32252 | | |
> | |
> |* 2 | WINDOW SORT PUSHED RANK| | 1 | 9387K|
> 388K|00:00:34.06 | 100K| 38026 | 32252 | 204M| 4789K| 8362K (3)|
> 192K|
> | 3 | PARTITION LIST SINGLE | | 1 | 9387K|
> 9503K|00:00:03.45 | 100K| 5774 | 0 | | |
> | |
> | 4 | *PARTITION RANGE ALL* | | 1 | 9387K|
> 9503K|00:00:02.51 | 100K| 5774 | 0 | | |
> | |
> | 5 | TABLE ACCESS FULL | SYSSTAT_METRICS | 27 | 9387K|
> 9503K|00:00:01.49 | 100K| 5774 | 0 | | |
> | |
>
> -------------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Predicate Information (identified by operation id):
> ---------------------------------------------------
>
> *1* - filter(("RR"=1 AND *"SNAP_TIME">=SYSDATE_at_!-3*))
> 2 - filter(RANK() OVER ( PARTITION BY
> "H"."STAT_NAME","H"."INSTANCE_NAME","H"."DATABASE_ID","H"."SERVER",TRUNC(INTERNAL_FUNCTION("H"."SNAP_TIME"))
> ORDER BY INTERNAL_FUNCTION("H"."SNAP_TIME") DESC )<=1)
>
> Here the statement uses much more partitions
> and the filter is much later.
> I am aware there is a slightly difference if I filter *snap_time >=
> sysdate - 3* in early with clause or after the PARTITON BY window
> function - but such oddities would be acceptable for this kind of data ;-).
>
> Does anyone have an idea how I can to PARTITION RANGE ITERATOR with a
> filter on the snap_time, which is the order/rank in PARTITION BY?
>
> (before anyone asks, the NO_INDEX is to avoid this "good" plan which
> doesn't change anything, but could be confusing)
> | 4 | PARTITION RANGE ITERATOR |
> | 1 | 3 | 51612 |00:00:00.05 | 20177 | | |
> |
> | 5 | TABLE ACCESS BY LOCAL INDEX ROWID BATCHED| SYSSTAT_METRICS
> | 4 | 3 | 51612 |00:00:00.04 | 20177 | | |
> |
> |* 6 | INDEX RANGE SCAN | I_SYSSTAT_METRICS
> | 1 | 3 | 51612 |00:00:00.01 | 174 | | |
> |
>
> --------------------------------------------------------------------------------------------------------------------------------------------------------
>
> Predicate Information (identified by operation id):
> ---------------------------------------------------
>
> 1 - filter("RR"=1)
> 2 - filter(RANK() OVER ( PARTITION BY
> "H"."STAT_NAME","H"."INSTANCE_NAME","H"."DATABASE_ID","H"."SERVER",TRUNC(INTERNAL_FUNCTION("H"."SNAP_TIME"))
> ORDER BY INTERNAL_FUNCTION("SNAP_TIME") DESC )<=1)
> 6 - access("SNAP_TIME">=SYSDATE_at_!-3)
>
>
> thank you for any advise,
> Martin
>
>
>
>
> Table definition:
> CREATE TABLE "H3G_SYSSTAT_METRICS"
> ( "STAT_NAME" VARCHAR2(64 BYTE) NOT NULL ENABLE,
> "SNAP_TIME" DATE NOT NULL ENABLE,
> "DATABASE_ID" NUMBER NOT NULL ENABLE,
> "INSTANCE_NAME" VARCHAR2(64 BYTE) NOT NULL ENABLE,
> "SERVER" VARCHAR2(64 BYTE) NOT NULL ENABLE,
> "STARTUP_TIME" DATE NOT NULL ENABLE,
> "VALUE" NUMBER NOT NULL ENABLE
> )
> PCTFREE 0 PCTUSED 40 INITRANS 1 MAXTRANS 255
> COMPRESS BASIC
> STORAGE(
> BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
> TABLESPACE "USERS"
> PARTITION BY LIST ("STAT_NAME")
> SUBPARTITION BY RANGE ("SNAP_TIME")
> (PARTITION "P2" VALUES ('CPU used by this session')
> PCTFREE 0 PCTUSED 40 INITRANS 1 MAXTRANS 255
> STORAGE(
> BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
> TABLESPACE "USERS"
> COMPRESS BASIC
> ( SUBPARTITION "P2_000000" VALUES LESS THAN (TO_DATE(' 2016-01-01
> 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
> TABLESPACE "USERS"
> COMPRESS BASIC ,
> SUBPARTITION "P2_201600" VALUES LESS THAN (TO_DATE(' 2017-01-01
> 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIAN'))
> TABLESPACE "USERS"
> ...
>
>
>
-- http://www.freelists.org/webpage/oracle-lReceived on Mon Oct 08 2018 - 14:52:49 CEST