Question Re: Materialized view with Parameter? in Technology Q&A

Materialized view with Parameter?

MCMartin — Fri, 29 Apr 2011 12:06:46 GMT

Is it possible to create a materialized view which uses a parameter during manual refresh? Something like

CREATE MATERIALIZED VIEW "DBA"."MyView" in system as select * from X where X.date > PARAM

So that e.g. each week the materialized view can be refreshed to reflect the values of last week or so...

Re: Materialized view with Parameter?

Former Member — Fri, 29 Apr 2011 13:34:47 GMT

No, not at this time.

Re: Materialized view with Parameter?

VolkerBarth — Fri, 29 Apr 2011 18:50:41 GMT

I guess you do not want to use an ordinary view (e.g. something like

select * from x where datediff(dd, x.date, current date) >= 7

for performance reasons. May a global shared by all temporary table be of help? (I'm aware that temporary tables do not get used by view matching.)

Re: Materialized view with Parameter?

MCMartin — Mon, 02 May 2011 02:37:34 GMT

The workaround I use is an extra table just with the value of the parameter and then in the materialized view:

select * from X where X.date > (select max(PARAM) from paramtable)

Not elegant but it works.

Re: Materialized view with Parameter?

VolkerBarth — Mon, 02 May 2011 03:17:31 GMT

I'm assuming you are calling the MV explicitly in your queries (instead of relying on view matching)?

Re: Materialized view with Parameter?

MCMartin — Mon, 02 May 2011 07:24:09 GMT

yes, I am not using the view for the optimizer

Re: Materialized view with Parameter?

Former Member — Mon, 02 May 2011 17:16:48 GMT

If you maintain 'paramtable' with exactly one row representing the current parameter value, then your view can be declared immediate and also can be used for cost-based view matching by the SQL Anywhere Optimizer for queries which don't mention 'paramtable': to let the optimizer know that paramtable has exactly one row, add a primary key column. This is one solution. Other solutions exist as well.

Example:

create table paramtable (PK int not null primary key, A_PARAM int);

insert into paramtable (PK,A_PARAM) values (1, NULL);

update paramtable set A_PARAM=PARAM;

-- This materialized view can be declared immediate
-- and will be also used by the optimizer if the
-- query references only the table 'X'
CREATE MATERIALIZED VIEW "DBA"."MyView" in system as 
select * from X, paramtable
where X.date > paramtable.A_PARAM and paramtable.PK = 1;

Re: Materialized view with Parameter?

VolkerBarth — Tue, 03 May 2011 03:29:24 GMT

Am I right that a (CREATE) VARIABLE won't do, either, as it is connection-specific by default, and that would be non-deterministic, too?

(I'm asking as using such a variable would be a common way to parametrize a normal view.)

Re: Materialized view with Parameter?

VolkerBarth — Fri, 01 Feb 2013 14:50:48 GMT

(That would better asked as a separate question...): No, materialized views were introduced in v10.