https://stackoverflow.com/questions/23569538
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RussianIf you want to avoid table access full on r_attributfeld, you should try a nested loop on this table. Maybe you'll have to had a leading(r_rapport r_attributfeld) (or ordered hint) if Oracle "don't understand" what you want
How do I force access by index rowid in Oracle?
-
19-07-2023 - |
質問
I need help forcing Oracle to always use table access by index row id on table "r_rapport" (~60k rows) to subsequently avoid full table scans on "r_attributfeld" (~8m rows) . I have a query resulting in the following plan:
---------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 101 | 22220 | | 63518 (2)| 00:12:43 |
|* 1 | COUNT STOPKEY | | | | | | |
| 2 | VIEW | | 2870 | 616K| | 63518 (2)| 00:12:43 |
|* 3 | SORT ORDER BY STOPKEY | | 2870 | 313K| 696K| 63518 (2)| 00:12:43 |
|* 4 | FILTER | | | | | | |
|* 5 | HASH JOIN SEMI | | 2871 | 314K| | 51920 (2)| 00:10:24 |
|* 6 | HASH JOIN RIGHT SEMI | | 2871 | 299K| | 26084 (2)| 00:05:14 |
| 7 | VIEW | VW_NSO_1 | 214 | 1070 | | 5 (20)| 00:00:01 |
|* 8 | HASH JOIN | | 214 | 5350 | | 5 (20)| 00:00:01 |
|* 9 | INDEX RANGE SCAN | TEST7 | 141 | 1269 | | 2 (0)| 00:00:01 |
|* 10 | INDEX RANGE SCAN | TEST8 | 228 | 3648 | | 2 (0)| 00:00:01 |
|* 11 | HASH JOIN SEMI | | 5848 | 582K| | 26079 (2)| 00:05:13 |
|* 12 | HASH JOIN | | 6547 | 620K| | 243 (2)| 00:00:03 |
|* 13 | INDEX RANGE SCAN | TEST5 | 47 | 470 | | 2 (0)| 00:00:01 |
| 14 | TABLE ACCESS FULL | R_RAPPORT | 60730 | 5159K| | 240 (1)| 00:00:03 |
| 15 | VIEW | VW_SQ_3 | 334K| 1633K| | 25834 (2)| 00:05:11 |
|* 16 | HASH JOIN | | 334K| 14M| 10M| 25834 (2)| 00:05:11 |
| 17 | INDEX FAST FULL SCAN | TEST4 | 476K| 4656K| | 368 (2)| 00:00:05 |
|* 18 | HASH JOIN | | 343K| 11M| 11M| 24214 (2)| 00:04:51 |
|* 19 | TABLE ACCESS FULL | R_ATTRIBUTFELD | 343K| 7722K| | 20483 (2)| 00:04:06 |
| 20 | INDEX FAST FULL SCAN| TEST3 | 1670K| 17M| | 1324 (1)| 00:00:16 |
| 21 | VIEW | VW_SQ_2 | 334K| 1633K| | 25834 (2)| 00:05:11 |
|* 22 | HASH JOIN | | 334K| 14M| 10M| 25834 (2)| 00:05:11 |
| 23 | INDEX FAST FULL SCAN | TEST4 | 476K| 4656K| | 368 (2)| 00:00:05 |
|* 24 | HASH JOIN | | 343K| 11M| 11M| 24214 (2)| 00:04:51 |
|* 25 | TABLE ACCESS FULL | R_ATTRIBUTFELD | 343K| 7722K| | 20483 (2)| 00:04:06 |
| 26 | INDEX FAST FULL SCAN | TEST3 | 1670K| 17M| | 1324 (1)| 00:00:16 |
|* 27 | INDEX RANGE SCAN | TEST6 | 1 | 8 | | 8 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------------------
By adding a FIRST_ROWS(1) hint, this changes to the much more desired plan:
----------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 220 | 96 (0)| 00:00:02 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | VIEW | | 1 | 220 | 96 (0)| 00:00:02 |
|* 3 | FILTER | | | | | |
| 4 | NESTED LOOPS | | 1 | 97 | 16 (0)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID | R_RAPPORT | 60730 | 5159K| 6 (0)| 00:00:01 |
| 6 | INDEX FULL SCAN DESCENDING | IDX_R_RAPPORT_3 | 10 | | 2 (0)| 00:00:01 |
|* 7 | INDEX RANGE SCAN | TEST5 | 1 | 10 | 1 (0)| 00:00:01 |
| 8 | NESTED LOOPS | | 1 | 25 | 2 (0)| 00:00:01 |
|* 9 | INDEX RANGE SCAN | TEST7 | 141 | 1269 | 2 (0)| 00:00:01 |
|* 10 | INDEX UNIQUE SCAN | TEST8 | 1 | 16 | 0 (0)| 00:00:01 |
|* 11 | TABLE ACCESS BY INDEX ROWID | R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 12 | NESTED LOOPS | | 2 | 88 | 35 (0)| 00:00:01 |
| 13 | NESTED LOOPS | | 10 | 210 | 7 (0)| 00:00:01 |
|* 14 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 15 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 16 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 17 | TABLE ACCESS BY INDEX ROWID| R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 18 | NESTED LOOPS | | 2 | 88 | 35 (0)| 00:00:01 |
| 19 | NESTED LOOPS | | 10 | 210 | 7 (0)| 00:00:01 |
|* 20 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 21 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 22 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 23 | INDEX RANGE SCAN | TEST6 | 1 | 8 | 8 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------------------
Unfortunately this query is composed at runtime, and should there be three subrequests instead of the two here, it will ignore the FIRST_ROWS hint and again do multiple full table scans on 8 million rows. With the given data distribution access by rowid will always be faster (almost instant) while the plan Oracle prefers takes several seconds.
I tried using ROWID hints on both tables, before discovering those have been deprecated.
Any pointers will be appreciated.
=edit=
USE_NL & new Index
-----------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 101 | 22220 | 3994 (1)| 00:00:48 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | VIEW | | 102 | 22440 | 3994 (1)| 00:00:48 |
| 3 | NESTED LOOPS SEMI | | 1 | 102 | 16 (7)| 00:00:01 |
| 4 | NESTED LOOPS | | 1 | 97 | 11 (0)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID | R_RAPPORT | 58985 | 5011K| 10 (0)| 00:00:01 |
|* 6 | INDEX FULL SCAN DESCENDING | TEST12 | 1 | | 9 (0)| 00:00:01 |
|* 7 | TABLE ACCESS BY INDEX ROWID | R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 8 | NESTED LOOPS | | 2 | 88 | 35 (0)| 00:00:01 |
| 9 | NESTED LOOPS | | 10 | 210 | 7 (0)| 00:00:01 |
|* 10 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 11 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 12 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 13 | TABLE ACCESS BY INDEX ROWID| R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 14 | NESTED LOOPS | | 2 | 88 | 35 (0)| 00:00:01 |
| 15 | NESTED LOOPS | | 10 | 210 | 7 (0)| 00:00:01 |
|* 16 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 17 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 18 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 19 | INDEX RANGE SCAN | TEST6 | 1 | 8 | 8 (0)| 00:00:01 |
|* 20 | INDEX RANGE SCAN | TEST5 | 1 | 10 | 1 (0)| 00:00:01 |
|* 21 | VIEW | VW_NSO_1 | 105 | 525 | 5 (20)| 00:00:01 |
|* 22 | HASH JOIN | | 214 | 5350 | 5 (20)| 00:00:01 |
|* 23 | INDEX RANGE SCAN | TEST7 | 141 | 1269 | 2 (0)| 00:00:01 |
|* 24 | INDEX RANGE SCAN | TEST8 | 228 | 3648 | 2 (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------------------
SQL:
select /*+ FIRST_ROWS */ * from (
select *
from r_rapport a
where rb_id in (
select obj_id from obj_recht where obj_typ = 20 and obj_pid = 10065 and maske_id in (
select distinct maske_id
from obj_rechtmaske
where subj_pid = 10065
) )
and rb_id in (
select id from rb_buch where pid = 10065
)
and exists (
select /*+ USE_NL( c d ) */ 1
from r_teilanlage b, r_attribut c, r_attributfeld d
where a.id = b.r_id
and b.id = c.r_teilanlage_id
and c.id = d.r_attribut_id
and d.attributfeld_typ not in ( 20, 25, 40, 78, 79, 90, 92, 123, 124, 125, 126, 127 )
and lower( d.wert ) like lower( '%ä%' )
)
and exists (
select /*+ USE_NL( c d ) */ 1
from r_teilanlage b, r_attribut c, r_attributfeld d
where a.id = b.r_id
and b.id = c.r_teilanlage_id
and c.id = d.r_attribut_id
and d.attributfeld_typ not in ( 20, 25, 40, 78, 79, 90, 92, 123, 124, 125, 126, 127 )
and lower( d.wert ) like lower( '%ö%' )
)
and exists (
select /*+ USE_NL( c d ) */ 1
from r_teilanlage b, r_attribut c, r_attributfeld d
where a.id = b.r_id
and b.id = c.r_teilanlage_id
and c.id = d.r_attribut_id
and d.attributfeld_typ not in ( 20, 25, 40, 78, 79, 90, 92, 123, 124, 125, 126, 127 )
and lower( d.wert ) like lower( '%ä%' )
)
and exists (
select /*+ USE_NL( c d ) */ 1
from r_teilanlage b, r_attribut c, r_attributfeld d
where a.id = b.r_id
and b.id = c.r_teilanlage_id
and c.id = d.r_attribut_id
and d.attributfeld_typ not in ( 20, 25, 40, 78, 79, 90, 92, 123, 124, 125, 126, 127 )
and lower( d.wert ) like lower( '%ö%' )
)
and a.id not in (
select r_id from r_gelesen where ma_id = 144
)
order by a.open_stamp desc
) where rownum <= 101;
and its plan:
----------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 220 | 1195K (1)| 03:59:08 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | VIEW | | 1 | 220 | 1195K (1)| 03:59:08 |
|* 3 | FILTER | | | | | |
| 4 | NESTED LOOPS SEMI | | 3213 | 320K| 1018K (1)| 03:23:47 |
| 5 | NESTED LOOPS | | 6547 | 620K| 82249 (1)| 00:16:27 |
| 6 | TABLE ACCESS BY INDEX ROWID | R_RAPPORT | 60730 | 5159K| 21493 (1)| 00:04:18 |
| 7 | INDEX FULL SCAN DESCENDING | IDX_R_RAPPORT_3 | 60730 | | 152 (1)| 00:00:02 |
|* 8 | INDEX RANGE SCAN | TEST5 | 1 | 10 | 1 (0)| 00:00:01 |
|* 9 | VIEW | VW_NSO_1 | 105 | 525 | 143 (0)| 00:00:02 |
| 10 | NESTED LOOPS | | 214 | 5350 | 143 (0)| 00:00:02 |
|* 11 | INDEX RANGE SCAN | TEST7 | 141 | 1269 | 2 (0)| 00:00:01 |
|* 12 | INDEX RANGE SCAN | TEST8 | 2 | 32 | 1 (0)| 00:00:01 |
|* 13 | TABLE ACCESS BY INDEX ROWID | R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 14 | NESTED LOOPS | | 6 | 264 | 97 (0)| 00:00:02 |
| 15 | NESTED LOOPS | | 30 | 630 | 13 (0)| 00:00:01 |
|* 16 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 17 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 18 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 19 | TABLE ACCESS BY INDEX ROWID | R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 20 | NESTED LOOPS | | 6 | 264 | 97 (0)| 00:00:02 |
| 21 | NESTED LOOPS | | 30 | 630 | 13 (0)| 00:00:01 |
|* 22 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 23 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 24 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 25 | TABLE ACCESS BY INDEX ROWID | R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 26 | NESTED LOOPS | | 6 | 264 | 97 (0)| 00:00:02 |
| 27 | NESTED LOOPS | | 30 | 630 | 13 (0)| 00:00:01 |
|* 28 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 29 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 30 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 31 | TABLE ACCESS BY INDEX ROWID| R_ATTRIBUTFELD | 1 | 23 | 3 (0)| 00:00:01 |
| 32 | NESTED LOOPS | | 6 | 264 | 97 (0)| 00:00:02 |
| 33 | NESTED LOOPS | | 30 | 630 | 13 (0)| 00:00:01 |
|* 34 | INDEX RANGE SCAN | TEST4 | 9 | 90 | 3 (0)| 00:00:01 |
|* 35 | INDEX RANGE SCAN | TEST3 | 3 | 33 | 2 (0)| 00:00:01 |
|* 36 | INDEX RANGE SCAN | IDX_R_ATTRIBUTFELD_1 | 6 | | 2 (0)| 00:00:01 |
|* 37 | INDEX RANGE SCAN | TEST6 | 1 | 8 | 8 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------------------
A horrible, horrible cost estimate as this query completes instantly.
解決
他のヒント
Not always what you think is better plan is realy better plan. To return you first rows fast is right way to use nested loops and rowid acces. But if you want return all result set fast it is more efficient to use hash join even if you are joining by rowid("select * from tab where rowid in (...)" or "... join tab on tab.rowid = ...'). So I think Oracle picked right plan for you.
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