Add efficient count method for aiida.orm.groups.Group
#2567
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| """ | ||
| from aiida.backends.sqlalchemy import get_scoped_session | ||
| session = get_scoped_session() | ||
| return session.query(self.MODEL_CLASS).join(self.MODEL_CLASS.dbnodes).filter(DbGroup.id == self.pk).count() |
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Can't this be just piped to len(self.nodes)? This, below, should do the same thing? (see len in the property returned by nodes?
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That's what I was originally using, but at least for the SqlA implementation it was a factor 8 slower on my production database
giovannipizzi
approved these changes
Mar 4, 2019
Before the only way to get the number of entries in a `Group` was through the iterator `nodes` and call `len()` on it. However, this is almost always not the fastest way. Given that the count is used often in for example `verdi group list -C` it is worthwhile to have a `count` method that operates as direct on the database layer as possible.
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Fixes #1948
Before the only way to get the number of entries in a
Groupwasthrough the iterator
nodesand calllen()on it. However, this isalmost always not the fastest way. Given that the count is used often in
for example
verdi group list -Cit is worthwhile to have acountmethod that operates as direct on the database layer as possible.