RE: "JPPD bypassed: DISTINCT clause" in 19c
Date: Fri, 4 Sep 2020 12:20:28 +0000
Message-ID: <28461_1599222046_5F52311E_28461_2580_1_71c439200f2545d389b872cfb95bcdf0_at_vontobel.com>
Believe it or not, JSON is the culprit. The problem is much more serious than initially reported. JSON entirely shuts off cost based JPPD in 19c!
Find the queries below (the table definitions are from https://nenadnoveljic.com/blog/join-predicate-push-down-additional-phase/ ):
With distinct:
explain plan for
Without distinct:
explain plan for
select /*+ qb_name(QB_MAIN) */
JSON_OBJECT (
'id' VALUE 1
RETURNING VARCHAR2 (10)
STRICT)
from t1 left outer join
( select /*+ qb_name(QB_MIDDLE) */ distinct t2.n2
from
t2 ,
( select /*+ qb_name(QB_INNER ) */ distinct t3.n2
from t3, t4
where t4.n1 = t3.n1
) v2
where v2.n2(+) = t2.n1
) v1 on v1.n2 = t1.n1
;
JPPD: JPPD bypassed: DISTINCT clause.
JPPD: JPPD bypassed: DISTINCT clause.
select /*+ qb_name(QB_MAIN) */
JSON_OBJECT (
'id' VALUE 1
RETURNING VARCHAR2 (10)
STRICT)
from t1 left outer join
( select /*+ qb_name(QB_MIDDLE) */ t2.n2
from
t2 ,
( select /*+ qb_name(QB_INNER ) */ t3.n2
from t3, t4
where t4.n1 = t3.n1
) v2
where v2.n2(+) = t2.n1
) v1 on v1.n2 = t1.n1
;
JPPD: JPPD bypassed: View has unsupported constructs.
Without JSON:
explain plan for
select /*+ qb_name(QB_MAIN) */
1
from t1 left outer join
( select /*+ qb_name(QB_MIDDLE) */ t2.n2
from
t2 ,
( select /*+ qb_name(QB_INNER ) */ t3.n2
from t3, t4
where t4.n1 = t3.n1
) v2
where v2.n2(+) = t2.n1
) v1 on v1.n2 = t1.n1
;
JPPD: Considering Cost-based predicate pushdown from query block SEL$1A44BB0C (#1) Cost-based predicate pushdown (JPPD)
JPPD: Checking validity of push-down in query block QB_MIDDLE (#2) JPPD: Checking validity of push-down from query block QB_MIDDLE (#2) to query block QB_INNER (#3) JPPD: Passed validity checks JPPD: JPPD: Pushdown from query block QB_MIDDLE (#2) passed validity checks.
Best regards,
Nenad
Please consider the environment before printing this e-mail. Bitte denken Sie an die Umwelt, bevor Sie dieses E-Mail drucken.
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css">p { font-family: Arial;font-size:9pt }</style>
</head>
<body>
<p>
<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.
For further information about data privacy at Vontobel Group please consult <a href="https://www.vontobel.com">www.vontobel.com</a>.<br />
</p>
</body>
</html>
-- http://www.freelists.org/webpage/oracle-lReceived on Fri Sep 04 2020 - 14:20:28 CEST