Where clause using Expression tree builder - linq

Question

I have to fetch data from database and filter data using the linq where clause.
My filter is an integer column and it contains value more than 1000.
What i am doing in the code is, breaking this huge array into chunk of 1000's of each and putting it in the where clause of a base query
int j = 0;
int batchsize = 1000;
while ((j * batchsize) < items.Count())
{
List<long> batch = items.Skip(j * batchsize)
.Take(batchsize).ToList();
prequery = prequery.Where(x => batch.Contains(x.Id));
j++;
}
the query which is getting generated in sql is below,
SELECT
x.name,
x.email
FROM
table x
WHERE
x.Id IN (1,2,3,...,1000) AND
x.Id IN (1001,1002,1003....,2000)
i want the query to be generated as below,
SELECT
x.name,
x.email
FROM
table x
WHERE
x.Id IN (1,2,3,...,1000) OR
x.Id IN (1001,1002,1003....,2000)
can i achieve this using expression tree builder and generate the query dynamically, if so please help in doing

Answer 1

you could use the "Concat" API:
int j = 0;
int batchsize = 1000;
IQueryable<YourType> finalQuery = null;
while ((j * batchsize) < items.Count())
{
List<long> batch = items.Skip(j * batchsize)
.Take(batchsize).ToList();
if (finalQuery == null) {
finalQuery = prequery.Where(x => batch.Contains(x.Id));
}
else
finalQuery = finalQuery.Concat (prequery.Where(x => batch.Contains(x.Id)));
j++;
}
This will logically get you what you want: basically you want an "OR" operation between batches. Concat is translated into an "UNION ALL" database call.
BUT ... I don't understand why are you doing this, after all you are grabbing all your data, chunks are not helping you because in the end there will be only one statement executed.