indexes : SYS_CHANGED_CHRONOS vs SYS_CHANGED_CHRONOS2 performances

Tue, 22 Oct 2019 09:38:06 +0000

Hi everyone,

before giving the context and my observations, here is my question : for what kind of queries the SYS_CHANGED_CHRONOS and SYS_CHANGED_CHRONOS2 indexes are created ?

Yesterday, I observed that the chronos detail was really slow to load.

In the query logs, the chronos detail has generated one query per selected entity (chronos detail options).
The idea is to get the primary key of each entity linked to the entity.
There is no other query in the logs about chronos detail.

So, I guess, but I can’t confirm it without proof, that the primary keys from the previous queries are used by the following SYS_CHANGED queries :

select K_TABLE, D_CHANGE, USERNAME, OPERATION, K_1, K_2, K_3, MILLI,
"COMMENT" from "GERM"."SYS_CHANGED" where ((K_1 = :key and K_TABLE in
(:param1)) or (K_2 = :key and K_TABLE in (:param2, :param3, :param4)))
and (D_CHANGE >= :mindate) and (D_CHANGE < :maxdate) order by D_CHANGE,
K_TABLE, K_2, MILLI, OPERATION;

select distinct USERNAME, D_CHANGE from "GERM"."SYS_CHANGED" where
((K_1 = :key and K_TABLE in (:param1)) or (K_2 = :key and K_TABLE in
(:param2, :param3, :param4))) and (D_CHANGE >= :mindate) and (D_CHANGE
< :maxdate) order by D_CHANGE DESC;

Each of these queries exists in a lot of versions because of a variation in the number of parameters for K_TABLE field.

When I consult the execution plan of the above queries (Oracle - SQL Developer), I observe that the first one is using SYS_CHANGED_CHRONOS (K_2, K_TABLE, D_CHANGE, USERNAME) index and the second one, SYS_CHANGED_CHRONOS2 (D_CHANGE, K_TABLE, K_1, K_2) index.
For each query, I can consult the execution plan with SYS_CHANGED_CHRONOS or SYS_CHANGED_CHRONOS2 index.
The cost is almost the same between these two indexes. So, the choice between them seems to be a really complicated choice for Oracle.
In the database, SYS_CHANGED_CHRONOS is better in a lot of situations.

So, for what kind of queries the SYS_CHANGED_CHRONOS and SYS_CHANGED_CHRONOS2 indexes are created ?

KR,

Eric

Create new indexes in tables

Wed, 05 Jun 2019 07:31:51 +0000

Hello,

Last Friday, I created several Indexes on different tables. Indeed, we need those indexes to optimize the matching on the customer ID during the datasync and when the customer uses the API.
Today all those indexes have disappeared. What's happen between last Friday and today? An upgrade DB was launched. It seems this action destroys those customs indexes.
Is it the standard behavior? If it is, how to create custom indexes that are not destroy on each db upgrade?

thanks for the help,

Laurent

PS: the "Tools" option into the dbeditor didn't exist anymore into Efficy11.x

DBEditor new functionnality : Indexes

Mon, 18 Jan 2016 09:29:20 +0000

From Efficy 2014 R6640 in the DBEditor there is a new tool to add compute additional indexes to speed-up list queries, also for custom entities.

Is it about Database Native Indexes? Where is it? How this is working?

Can we have more information of indexes which have been put in place to improve search performance?

Efficy Overflow Q&A - Recent questions tagged indexes

indexes : SYS_CHANGED_CHRONOS vs SYS_CHANGED_CHRONOS2 performances

Create new indexes in tables

DBEditor new functionnality : Indexes