Noveljic Nenad
2018-12-06 14:28:13 UTC
The optimizer generates an expensive JPPD plan on a 12.2 database. In contrast, I'm getting a much cheaper plan with "_push_join_predicate"=false.
It's a complex query, so I couldn't build a model so far, but I can reproduce the bad plan at will.
So, I'm going to describe the problem by using the information from the CBO (10053) trace.
First, the optimizer calculates the cost of applying JPPD to three different query blocks - annotated as: #10, #11 and #12 :
JPPD: Checking validity of push-down in query block SET$BADDE9FB_1 (#4)
JPPD: Checking validity of push-down from query block SET$BADDE9FB_1 (#4) to query block SEL$2DE89145 (#10)
Check Basic Validity for Non-Union View for query block SEL$2DE89145 (#10)
JPPD: Passed validity checks
JPPD: Checking validity of push-down from query block SET$BADDE9FB_1 (#4) to query block SEL$41289C4A (#11)
Check Basic Validity for Non-Union View for query block SEL$41289C4A (#11)
JPPD: Passed validity checks
JPPD: Checking validity of push-down from query block SET$BADDE9FB_1 (#4) to query block SEL$A0D20652 (#12)
Check Basic Validity for Non-Union View for query block SEL$A0D20652 (#12)
JPPD: Passed validity checks
JPPD: JPPD: Pushdown from query block SET$BADDE9FB_1 (#4) passed validity checks.
Join-Predicate push-down on query block SET$BADDE9FB_1 (#4)
JPPD: Using search type: linear
JPPD: Considering join predicate push-down
JPPD: Starting iteration 1, state space = (10,11,12) : (0,0,0)
JPPD: Updated best state, Cost = 41463.286373
JPPD: Starting iteration 2, state space = (10,11,12) : (1,0,0)
JPPD: Not update best state, Cost = 41463.286373
JPPD: Starting iteration 3, state space = (10,11,12) : (0,1,0)
JPPD: Not update best state, Cost = 41463.286373
JPPD: Starting iteration 4, state space = (10,11,12) : (0,0,1)
JPPD: Not update best state, Cost = 41463.286373
As you can see, the state space (10,11,12) : (0,0,0) is the one with the lowest cost. In other words, it would be cheapest not to do JPPD at all.
Also the subsequent log entry indicates that JPPD shouldn't be done:
JPPD: Will not use JPPD from query block SET$BADDE9FB_1 (#4)
But later on, strangely, the optimizer ignores that and, in the end, performs JPPD on all three query blocks:
JPPD: Checking validity of push-down in query block SET$BADDE9FB_1 (#4)
JPPD: JPPD: Pushdown from query block SET$BADDE9FB_1 (#4) passed validity checks.
JPPD: Performing join predicate push-down (final phase) from query block SET$BADDE9FB_1 (#4) to query block SEL$A0D20652 (#12)
JPPD: Pushing predicate "BRIEFANREDE"."VIN01ID"(+)="VIN01"."ID"
from query block SET$BADDE9FB_1 (#4) to query block SEL$A0D20652 (#12)
JPPD: Push dest of pred 0xa8637960 is qb 0xbac44950:query block SEL$A0D20652 (#12)
JPPD: Performing join predicate push-down (final phase) from query block SET$BADDE9FB_1 (#4) to query block SEL$41289C4A (#11)
JPPD: Pushing predicate "ORG12_RM_GESCHAEFTSFELD"."GES01_ID"(+)="GES01"."ID"
from query block SET$BADDE9FB_1 (#4) to query block SEL$41289C4A (#11)
JPPD: Push dest of pred 0xa8633870 is qb 0xcbbc3de8:query block SEL$41289C4A (#11)
JPPD: Performing join predicate push-down (final phase) from query block SET$BADDE9FB_1 (#4) to query block SEL$2DE89145 (#10)
JPPD: Pushing predicate "EAM"."GES01_GESCHAEFTSBEZIEHUNG_GBZ"(+)="VIN01"."GES01_GBZ_GBZ"
from query block SET$BADDE9FB_1 (#4) to query block SEL$2DE89145 (#10)
JPPD: Push dest of pred 0x8fa13010 is qb 0x858777a8:query block SEL$2DE89145 (#10)
In the trace I haven't found any clue about what led the optimizer to suddenly start doing JPPD.
First and foremost, have I misinterpreted the trace?
If not, is anyone aware of any circumstances which could cause such behavior?
Best regards,
Nenad
https://nenadnoveljic.com/blog
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It's a complex query, so I couldn't build a model so far, but I can reproduce the bad plan at will.
So, I'm going to describe the problem by using the information from the CBO (10053) trace.
First, the optimizer calculates the cost of applying JPPD to three different query blocks - annotated as: #10, #11 and #12 :
JPPD: Checking validity of push-down in query block SET$BADDE9FB_1 (#4)
JPPD: Checking validity of push-down from query block SET$BADDE9FB_1 (#4) to query block SEL$2DE89145 (#10)
Check Basic Validity for Non-Union View for query block SEL$2DE89145 (#10)
JPPD: Passed validity checks
JPPD: Checking validity of push-down from query block SET$BADDE9FB_1 (#4) to query block SEL$41289C4A (#11)
Check Basic Validity for Non-Union View for query block SEL$41289C4A (#11)
JPPD: Passed validity checks
JPPD: Checking validity of push-down from query block SET$BADDE9FB_1 (#4) to query block SEL$A0D20652 (#12)
Check Basic Validity for Non-Union View for query block SEL$A0D20652 (#12)
JPPD: Passed validity checks
JPPD: JPPD: Pushdown from query block SET$BADDE9FB_1 (#4) passed validity checks.
Join-Predicate push-down on query block SET$BADDE9FB_1 (#4)
JPPD: Using search type: linear
JPPD: Considering join predicate push-down
JPPD: Starting iteration 1, state space = (10,11,12) : (0,0,0)
JPPD: Updated best state, Cost = 41463.286373
JPPD: Starting iteration 2, state space = (10,11,12) : (1,0,0)
JPPD: Not update best state, Cost = 41463.286373
JPPD: Starting iteration 3, state space = (10,11,12) : (0,1,0)
JPPD: Not update best state, Cost = 41463.286373
JPPD: Starting iteration 4, state space = (10,11,12) : (0,0,1)
JPPD: Not update best state, Cost = 41463.286373
As you can see, the state space (10,11,12) : (0,0,0) is the one with the lowest cost. In other words, it would be cheapest not to do JPPD at all.
Also the subsequent log entry indicates that JPPD shouldn't be done:
JPPD: Will not use JPPD from query block SET$BADDE9FB_1 (#4)
But later on, strangely, the optimizer ignores that and, in the end, performs JPPD on all three query blocks:
JPPD: Checking validity of push-down in query block SET$BADDE9FB_1 (#4)
JPPD: JPPD: Pushdown from query block SET$BADDE9FB_1 (#4) passed validity checks.
JPPD: Performing join predicate push-down (final phase) from query block SET$BADDE9FB_1 (#4) to query block SEL$A0D20652 (#12)
JPPD: Pushing predicate "BRIEFANREDE"."VIN01ID"(+)="VIN01"."ID"
from query block SET$BADDE9FB_1 (#4) to query block SEL$A0D20652 (#12)
JPPD: Push dest of pred 0xa8637960 is qb 0xbac44950:query block SEL$A0D20652 (#12)
JPPD: Performing join predicate push-down (final phase) from query block SET$BADDE9FB_1 (#4) to query block SEL$41289C4A (#11)
JPPD: Pushing predicate "ORG12_RM_GESCHAEFTSFELD"."GES01_ID"(+)="GES01"."ID"
from query block SET$BADDE9FB_1 (#4) to query block SEL$41289C4A (#11)
JPPD: Push dest of pred 0xa8633870 is qb 0xcbbc3de8:query block SEL$41289C4A (#11)
JPPD: Performing join predicate push-down (final phase) from query block SET$BADDE9FB_1 (#4) to query block SEL$2DE89145 (#10)
JPPD: Pushing predicate "EAM"."GES01_GESCHAEFTSBEZIEHUNG_GBZ"(+)="VIN01"."GES01_GBZ_GBZ"
from query block SET$BADDE9FB_1 (#4) to query block SEL$2DE89145 (#10)
JPPD: Push dest of pred 0x8fa13010 is qb 0x858777a8:query block SEL$2DE89145 (#10)
In the trace I haven't found any clue about what led the optimizer to suddenly start doing JPPD.
First and foremost, have I misinterpreted the trace?
If not, is anyone aware of any circumstances which could cause such behavior?
Best regards,
Nenad
https://nenadnoveljic.com/blog
____________________________________________________
Please consider the environment before printing this e-mail.
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<br>Important Notice</br>
<br />
This message is intended only for the individual named. It may contain confidential or privileged information. If you are not the named addressee you should in particular not disseminate, distribute, modify or copy this e-mail. Please notify the sender immediately by e-mail, if you have received this message by mistake and delete it from your system.<br />
Without prejudice to any contractual agreements between you and us which shall prevail in any case, we take it as your authorization to correspond with you by e-mail if you send us messages by e-mail. However, we reserve the right not to execute orders and instructions transmitted by e-mail at any time and without further explanation.<br />
E-mail transmission may not be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete. Also processing of incoming e-mails cannot be guaranteed. All liability of Vontobel Holding Ltd. and any of its affiliates (hereinafter collectively referred to as "Vontobel Group") for any damages resulting from e-mail use is excluded. You are advised that urgent and time sensitive messages should not be sent by e-mail and if verification is required please request a printed version.</br>
Please note that all e-mail communications to and from the Vontobel Group are subject to electronic storage and review by Vontobel Group. Unless stated to the contrary and without prejudice to any contractual agreements between you and Vontobel Group which shall prevail in any case, e-mail-communication is for informational purposes only and is not intended as an offer or solicitation for the purchase or sale of any financial instrument or as an official confirmation of any transaction.<br />
The legal basis for the processing of your personal data is the legitimate interest to develop a commercial relationship with you, as well as your consent to forward you commercial communications. You can exercise, at any time and under the terms established under current regulation, your rights. If you prefer not to receive any further communications, please contact your client relationship manager if you are a client of Vontobel Group or notify the sender.
Please note for an exact reference to the affected group entity the corporate e-mail signature.
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