Re: Tuning large aggregation query
- From: Mohamed Houri <mohamed.houri@xxxxxxxxx>
- To: kennethnaim@xxxxxxxxx
- Date: Fri, 4 Apr 2014 16:13:59 +0200
I can see in the plan that there are several operations that have not been
started at all
----------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name
| Starts | E-Rows | A-Rows | A-Time |
----------------------------------------------------------------------------------------------------------------------------------
| 0 | MERGE STATEMENT |
| 0 | | 0 |00:00:00.01 |
| 1 | MERGE | TARGET_TABLE
| 0 | | 0 |00:00:00.01 |
| 2 | PX COORDINATOR |
| 0 | | 0 |00:00:00.01 |
| 3 | PX SEND QC (RANDOM) | :TQ10002
| 0 | 4061K| 0 |00:00:00.01 |
| 4 | VIEW |
| 0 | | 0 |00:00:00.01 |
| 5 | NESTED LOOPS |
| 0 | 4061K| 0 |00:00:00.01 |
| 6 | NESTED LOOPS |
| 0 | 4061K| 0 |00:00:00.01 |
| 7 | VIEW |
| 0 | 3900K| 0 |00:00:00.01 |
| 8 | SORT GROUP BY |
| 0 | 3900K| 0 |00:00:00.01 |
| 9 | PX RECEIVE |
| 0 | 3900K| 0 |00:00:00.01 |
| 10 | PX SEND HASH | :TQ10001
| 0 | 3900K| 0 |00:00:00.01 |
| 11 | NESTED LOOPS |
| 1 | 3900K| 4135K|00:05:09.10 |
| 12 | NESTED LOOPS |
| 1 | 3900K| 4135K|00:02:26.62 |
| 13 | BUFFER SORT |
| 1 | | 229K|00:01:29.17 |
| 14 | PX RECEIVE |
| 1 | | 229K|00:01:28.21 |
| 15 | PX SEND ROUND-ROBIN | :TQ10000
| 0 | | 0 |00:00:00.01 |
| 16 | TABLE ACCESS BY GLOBAL INDEX ROWID| BASE_TABLE
| 0 | 3900K| 0 |00:00:00.01 |
| 17 | INDEX FULL SCAN | PK_BASE_TABLE
| 0 | 3900K| 0 |00:00:00.01 |
| 18 | PARTITION LIST ITERATOR |
| 229K| 1 | 4135K|00:00:48.82 |
|* 19 | INDEX RANGE SCAN | IDX_SALES_DATA
| 229K| 1 | 4135K|00:00:36.71 |
| 20 | TABLE ACCESS BY LOCAL INDEX ROWID | SALES_DATA
| 4135K| 1 | 4135K|00:02:21.94 |
| 21 | PARTITION LIST ITERATOR |
| 0 | 1 | 0 |00:00:00.01 |
|* 22 | INDEX RANGE SCAN |
IDX_T1704_ADVSTOREITEM | 0 | 1 | 0 |00:00:00.01 |
|* 23 | TABLE ACCESS BY LOCAL INDEX ROWID | TARGET_TABLE
| 0 | 1 | 0 |00:00:00.01 |
----------------------------------------------------------------------------------------------------------------------------------
All those operations signaled in this color have not been started. For the
remaining operations, operation 20 seems to be the most consuming one.
Have you a plan with a predicate part?
What is the definition of the index IDX_SALES_DATA. The CBO is doing a
wrong estimation when accessing this index which might lead to a wrong
since it looks like the starting operation
Best regards
Mohamed Houri
www.hourim.wordpress.com
2014-04-04 16:02 GMT+02:00 Kenneth Naim <kennethnaim@xxxxxxxxx>:
> What wait events are seeing when the query is running? How many columns
> are in each of the tables?
>
> -----Original Message-----
> From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
> On Behalf Of Thomas Kellerer
> Sent: Friday, April 04, 2014 9:12 AM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: Tuning large aggregation query
>
> Hi,
>
> for reporting purposes we are maintaining some denormalized,
> pre-aggregated tables in our OLTP database.
>
> These queries are aggregating sales and other related data from several
> source tables into one aggregation table.
>
> Our problem is that the aggregation of some 70 million rows into approx. 4
> million rows is quite slow.
>
> As far as I can tell, most of the time is lost when doing the actual
> aggregation.
> The join itself is quite fast, but aggregating 70 million rows needs a
> huge amount of memory (or temp-space)
>
> I uploaded to the execution plan to pastebin to preserve formatting:
> http://pastebin.com/XfEvB3z9 (You need to disable word-wrapping though)
>
> The basic structure of the statement looks like this:
>
> select base_table.pk_col_1,
> base_table.pk_col_2,
> base_table.pk_col_3,
> sum(....),
> sum(...),
> min(...),
> .... and another approx. 100 columns ...
> from base_table
> join sales_data on ...
> group by base_table.pk_col_1,
> base_table.pk_col_2,
> base_table.pk_col_3
>
> There is a 1:N relation between base_table and sales_data.
>
> Sales_data essentially stores sales information for products on a per-day,
> sale and store level.
> The goal of the aggregation is to sum up that daily information to a
> product/store level.
>
> sales_data contains about 70 million rows, base_table contains about 4
> million rows, so the result of the aggregation is again 4 million rows.
> sales_data is partitioned by the region in which the stores are located
> (and that partitioning cannot be changed).
>
> We applied the same partitioning scheme to base_table and target_table in
> the hope that this will make the parallel execution more efficient, but
> changing from unpartitioned to partitioned didn't improve the queries (but
> didn't make them worse either). We tried various indexes (in additioin to
> the PK index that is already used for the JOIN). But apparently for the
> type of query there isn't much an index can do.
>
> The main time is spent doing the aggregation.
> I confirmed that by only running the select statement that's inside the
> merge and that takes nearly as long as the merge itself.
>
> We were able to improve the whole process a bit by using parallel
> execution, but the runtimes are still way too high for the "window" we have
> in the night to prepare the data. The target would be that a single merge
> like that runs in about 10 minutes, currently it's around 60minutes.
>
> The test server runs Oracle 11.2.0.4 on a Windows 2008R2 server with 64GB
> RAM, a 8 spindle RAID 10 attached and 6 cores (12 CPUs).
>
> I can provide more Oracle configuration parameters if needed.
>
> The production server also runs Oracle 11.2.0.4 on Windows Server 2008R2,
> has 32 cores (64CPUs), 192GB RAM But we will not be able to test this on
> the real production hardware - and the number of rows in production will
> probably be 4-5 times bigger.
>
>
> I am looking for ideas on how to improve the runtime of those statements.
> Just some pointers on what things I could try out to either optimize the
> query itself or tune the Oracle configuration
>
> Thanks
> Thomas
>
>
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
--
Bien Respectueusement
Mohamed Houri
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