sql - Is there a Selectivity Clause to inject selectivity directly in PostgreSQL similar to IBM DB2 -

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To provide additional selection information with basic forecasts to help IBM DB2 query optimization Support for:

SELECTIVITY clause can only be used with basic forecasts (as defined in the SQL context), as if it is not liked or elapsed. A lower selectivity value (very small number) will tell DB2 that qualitative low rows (and encourage the use of defined indexes on that column) will qualify. A high selectivity value (about 1) will mean the opposite. An example from

: 

  SELECT c1, c2, c3, from t1, t2, t3 WHERE T1.x = T2.x and T2 .y = T3.y and T1.x & gt; =? Selectivity 0.00001 and T2.y & gt; ? Selectivity 0.5 and T3.z =? Selection 0.2 and T3.w =?

I am looking for a similar facility in PostgrassQL which by which we can choose directly as part of the query regarding the selectivity or at least affiliation of each municipality. Does anyone exist? Or is there any work on this front? If no work is going on, how should I implement this feature?

Additional note: Selector = Cardinality / (Number of records) is a part of the Tupe in an inventive-inspired selective table which is consoling and contentious. The choice of relation depends on the choice of all the predictions related to the relationship.

I am looking for a similar feature in PostgreSQL by which we can be part of the query form In each relationship level, you can selectively select the ingenious or least selective selection. Does anyone exist?

There is nothing like this for the operator. You can modify the pg_statistic for tables, but it only gives you statistics within the ranges provided by the fake statistics model, for example, postgresqual inter-column Does not try to identify relations, he has no place to store such information and there is no way to see it.

Is there any work going on this front?

Nobody knows I can get more information in a post in Pgsql-Hackers mailing list.

If there is no work on this, how should I start to implement this feature?

Again, I picked it up on pgsql-hackers, however, before doing so, postgre about question signals read something about the community policy of SQL.

The example for cost hinting (estimates from COST see the function for the View function) / code>) and ANALYZE To override, I think that you should be able to make some traction here, although you should expect a lot of bike-shading on the syntax.


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