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fixed slow query on normalized table; still 10x slower than current .map files

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Joey Hess 2014-03-13 09:38:20 -04:00
parent 66b8b9c094
commit 3e86d35e84
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7
doc/design/caching_database.mdwn
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@ -67,6 +67,7 @@ CachedKey
AssociatedFiles
keyId CachedKeyId Eq
associatedFile FilePath
KeyIdIndex keyId associatedFile
deriving Show
CachedMetaField
@ -86,6 +87,12 @@ LastFscked
With this, running 1000 joins to get the associated files of 1000
Keys took 5.6s with warm cache. (When done in the same `runSqlite` call.) Ouch!
Update: This performance was fixed by adding `KeyIdOutdex keyId associatedFile`,
which adds a uniqueness constraint on the tuple of key and associatedFile.
With this, 1000 queries takes 0.406s. Note that persistent is probably not
actually doing a join at the SQL level, so this could be sped up using
eg, esquelito.
Compare the above with 1000 calls to `associatedFiles`, which is approximately
as fast as just opening and reading 1000 files, so will take well under
0.05s with a **cold** cache.