[pytables-users] query execution time when looking for strings that don't exist

[d***@gmail.com]

Hi all,

I opened an issue on the github site
(https://github.com/PyTables/PyTables/issues/390) but I received no answer,
so I bet there is something wrong in my code.

My problem is that when I try to look for a string that is not contained in
the table, it takes a very long time to complete the query. For example:

I have an indexed StringCol in an hdf5 file with 2 billion rows. When I
execute a query using table.where and using this StringCol as the condition
(myStringCol == "whatever"), it takes 10 seconds to get the result of the
query (the result contains 70K rows approx.).

However, when I search for a string that is not contained in the DB (myStringCol
== "something_that_does_not_exist"), it takes 980 seconds to get the result
of the query (0 rows).

Do you guys observe the same behavior in your tables? I just want to know
if there is something wrong or if this is just the way pytables works.

Thanks!