SQL Server (2014) Query Optimization when using filter variable passed to procedure -


i looking optimization techniques or hint me move ahead problem have. using temp table in clause makes query run more 5 seconds, changing static value returns data under second. trying understand way optimize this.

-- details number of rows in table dept_activity table      - total rows                - 17,319,666     - rows (dept_id = 10)   - 36054  -- temp table  create table #tbl_depts (     id int identity(1, 1) primary key     ,dept_id integer );  -- example inserted 1 row based on conditions multiple department numbers inserted in temp table insert #tbl_depts(dept_id) values(10);  -- query takes more 5 seconds select activity_type,count(1) rc dept_activity da (         @filter_by_dept null         or da.depart_id in (             select td.dept_id             #tbl_depts td             )         ) group activity_type;  -- query takes less 500 milli seconds select activity_type,count(1) rc dept_activity da (         @filter_by_dept null         or da.depart_id in (                 10 -- changed static value             )         ) group activity_type;

what ways can optimize return data first query under second.

you're testing 1 value, isn't real case different?

the problem optimizer has here can't know how many rows temp. table in -clause find, it'll have make guess, , why result different. looking @ estimated row counts (+vs actual) might give insight on this.

if clause contains 1 criteria:

@filter_by_dept null or da.depart_id in

it might test happens if separate logic if blocks, 1 fetches all, , other filters data.

if that's not real case, might want test both option (recompile), result better plan, use (little bit) more cpu since plan re-generated every time. or constructing clause dynamic sql (either temp table optimizing away or statements, or doing full in clause if there isn't ridiculous amount of values), might ugly.


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