Question

I have two queries very similars, using the Linq ExecuteQuery method the first take 30 seconds, while the second query is inmediate.

I execute the queries too in Microsoft SQL Server Management Studio and the two queries have a response time of 0 seconds.

Query 1 (slow)

IEnumerable<ViewDataTanksDataDevice> res= 
this.ExecuteQuery<ViewDataTanksDataDevice>(
   "SELECT TOP 1 * FROM ViewDataTanksDataDevicesSB WHERE id_tank = {0} AND date >= {1} order by date", 
   new object[] { tankId, date });

Query 2 (fast)

IEnumerable<ViewDataTanksDataDevice> res= 
this.ExecuteQuery<ViewDataTanksDataDevice>(
   "SELECT TOP 1 * FROM ViewDataTanksDataDevicesSB WHERE id_tank = {0} AND date <= {1}     order by date desc", 
   new object[] { tankId, date });

Note 1: ViewDataTanksDataDevicesSB is a view with SCHEMA BINDING, and it has two index

1. Index 1(id_tank, date asc)
2. Index 2(id_tank, date desc)

Note 2: If I execute first the second query the result is identical: Query1 slow and Query 2 fast.

Note 3: The view have millions of registers, and the the results are identical for differents dates and tanks.

Answer 1

I resolved it after one week, viewing the execution plan (thanks Yahia by the suggestion)!!!

In the two queries I specified the INDEX (thanks Denis) and I had to specify the hint NOEXPAND.

NOEXPAND explanation can be found at: Table hints

So, the final queries are:

Query 1

IEnumerable<ViewDataTanksDataDevice> res= 
this.ExecuteQuery<ViewDataTanksDataDevice>(
   "SELECT TOP 1 * FROM ViewDataTanksDataDevicesSB with (index(IX_ViewDataTanksDataDevicesSB_TankIdDate) noexpand) WHERE id_tank = {0} AND date >= {1} order by date", 
   new object[] { tankId, date });

Query 2

IEnumerable<ViewDataTanksDataDevice> res= 
this.ExecuteQuery<ViewDataTanksDataDevice>(
   "SELECT TOP 1 * FROM ViewDataTanksDataDevicesSB with (index(IX_ViewDataTanksDataDevicesSB_TankIdDate) noexpand) WHERE id_tank = {0} AND date <= {1} order by date desc", 
   new object[] { tankId, date });