How can I determine how many sub-queries are required for a single top-level query on app engine (python)?
I am playing around with the IN operator, and I am curious if there is any way to be notified if I over-step my 30 sub-query limit.
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A:
If you try to execute a query which would spawn too many sub-queries then you would get this error:
BadArgumentError: Cannot satisfy query -- too many subqueries (max: 30, got 31). Probable cause: too many IN/!= filters in query.
If you wanted to check before trying to execute the query, you could check the length of the list which you are passing query - as long as it has 30 or fewer elements the query will be okay (as long as you aren't using the != operator in the query too; if you are, then each != query will double the number of sub-queries that you would otherwise have).
David Underhill
2010-09-29 21:16:46
David, what if I am passing a list to a property that is a ListProperty? Would the number of sub-queries be the product of the magnitude of the lists? I really wish the local datastore threw the same argument, I tried making mine throw that error and I couldn't get it to :/
Hamy
2010-09-30 00:32:02
Hamy: A ListProperty just generates 1 index entry per item in the list; no additional subqueries are needed to query a ListProperty.
Wooble
2010-09-30 03:33:42