change keys database to use IKey type with more efficient serialization

This breaks any existing keys database!

IKey serializes more efficiently than SKey, although this limits the
use of its Read/Show instances.

This makes the keys database use less disk space, and so should be a win.

Updated benchmark:

benchmarking keys database/getAssociatedFiles from 1000 (hit)
time                 64.04 μs   (63.95 μs .. 64.13 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 64.02 μs   (63.96 μs .. 64.08 μs)
std dev              218.2 ns   (172.5 ns .. 299.3 ns)

benchmarking keys database/getAssociatedFiles from 1000 (miss)
time                 52.53 μs   (52.18 μs .. 53.21 μs)
                     0.999 R²   (0.998 R² .. 1.000 R²)
mean                 52.31 μs   (52.18 μs .. 52.91 μs)
std dev              734.6 ns   (206.2 ns .. 1.623 μs)

benchmarking keys database/getAssociatedKey from 1000 (hit)
time                 64.60 μs   (64.46 μs .. 64.77 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 64.74 μs   (64.57 μs .. 65.20 μs)
std dev              900.2 ns   (389.7 ns .. 1.733 μs)

benchmarking keys database/getAssociatedKey from 1000 (miss)
time                 52.46 μs   (52.29 μs .. 52.68 μs)
                     1.000 R²   (0.999 R² .. 1.000 R²)
mean                 52.63 μs   (52.35 μs .. 53.37 μs)
std dev              1.362 μs   (562.7 ns .. 2.608 μs)
variance introduced by outliers: 24% (moderately inflated)

benchmarking keys database/addAssociatedFile to 1000 (old)
time                 487.3 μs   (484.7 μs .. 490.1 μs)
                     1.000 R²   (0.999 R² .. 1.000 R²)
mean                 490.9 μs   (487.8 μs .. 496.5 μs)
std dev              13.95 μs   (6.841 μs .. 22.03 μs)
variance introduced by outliers: 20% (moderately inflated)

benchmarking keys database/addAssociatedFile to 1000 (new)
time                 6.633 ms   (5.741 ms .. 7.751 ms)
                     0.905 R²   (0.850 R² .. 0.965 R²)
mean                 8.252 ms   (7.803 ms .. 8.602 ms)
std dev              1.126 ms   (900.3 μs .. 1.430 ms)
variance introduced by outliers: 72% (severely inflated)

benchmarking keys database/getAssociatedFiles from 10000 (hit)
time                 65.36 μs   (64.71 μs .. 66.37 μs)
                     0.998 R²   (0.995 R² .. 1.000 R²)
mean                 65.28 μs   (64.72 μs .. 66.45 μs)
std dev              2.576 μs   (920.8 ns .. 4.122 μs)
variance introduced by outliers: 42% (moderately inflated)

benchmarking keys database/getAssociatedFiles from 10000 (miss)
time                 52.34 μs   (52.25 μs .. 52.45 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 52.49 μs   (52.42 μs .. 52.59 μs)
std dev              255.4 ns   (205.8 ns .. 312.9 ns)

benchmarking keys database/getAssociatedKey from 10000 (hit)
time                 64.76 μs   (64.67 μs .. 64.84 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 64.67 μs   (64.62 μs .. 64.72 μs)
std dev              177.3 ns   (148.1 ns .. 217.1 ns)

benchmarking keys database/getAssociatedKey from 10000 (miss)
time                 52.75 μs   (52.66 μs .. 52.82 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 52.69 μs   (52.63 μs .. 52.75 μs)
std dev              210.6 ns   (173.7 ns .. 265.9 ns)

benchmarking keys database/addAssociatedFile to 10000 (old)
time                 489.7 μs   (488.7 μs .. 490.7 μs)
                     1.000 R²   (1.000 R² .. 1.000 R²)
mean                 490.4 μs   (489.6 μs .. 492.2 μs)
std dev              3.990 μs   (2.435 μs .. 7.604 μs)

benchmarking keys database/addAssociatedFile to 10000 (new)
time                 9.994 ms   (9.186 ms .. 10.74 ms)
                     0.959 R²   (0.928 R² .. 0.979 R²)
mean                 9.906 ms   (9.343 ms .. 10.40 ms)
std dev              1.384 ms   (1.051 ms .. 2.100 ms)
variance introduced by outliers: 69% (severely inflated)

1 files changed, 5 insertions, 5 deletions

diff --git a/Command/Benchmark.hs b/Command/Benchmark.hs
index b1cc9a830..bcfecc2dc 100644
--- a/Command/Benchmark.hs
+++ b/Command/Benchmark.hs
@@ -87,13 +87,13 @@ populateAssociatedFiles h num = do
 		SQL.addAssociatedFile (keyN n) (fileN n) (SQL.WriteHandle h)
 	H.flushDbQueue h
 
-keyN :: Int -> SKey
-keyN n = SKey ("key" ++ show n)
+keyN :: Int -> IKey
+keyN n = IKey ("key" ++ show n)
 
 fileN :: Int -> TopFilePath
 fileN n = asTopFilePath ("file" ++ show n)
 
-keyMiss :: SKey
+keyMiss :: IKey
 keyMiss = keyN 0 -- 0 is never stored
 
 fileMiss :: TopFilePath
@@ -114,8 +114,8 @@ benchDb tmpdir num = do
 instance NFData TopFilePath where
 	rnf = rnf . getTopFilePath
 
-instance NFData SKey where
-	rnf (SKey s) = rnf s
+instance NFData IKey where
+	rnf (IKey s) = rnf s
 	
 -- can't use Criterion's defaultMain here because it looks at
 -- command-line parameters