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Use SqlLite as a datastore

Update this, our DataStore is moving to RocksDB after becoming a Single Process Application once again.

Context and Problem Statement

We need a database of some sort to store key-value pairs in the application.

Decision Drivers

  • Should support arbitrary sized keys and values
  • Should support arbitrary database sizes and grow as needed (no 4GB limits)
  • Should allow multi-process access so that the CLI can run in parallel with the UI
  • Should support prefixed key scans so we can support multi key reverse index lookups
  • Should support at least 50,000 writes a second (a single game management like Skyrim involves this many involve this many writes)

Considered Options

Option Arbitrary Sized Keys Arbitrary Sized Values Arbitrary Database Size Multi-Process Access Prefixed Key Scans RW/sec
LMDB Yes Yes With restart on resize Yes Yes 1,200,000 reads / 1920 writes
LiteDB Yes Yes Yes Yes Yes 3230 reads / 517 writes
Sqlite Yes Yes Yes Yes Yes 182,348 reads / 139,489 writes
Filesystem Yes Yes Yes Yes Yes 34,072 reads / 7973 writes
Faster KV Yes Yes Yes No No N/A
RocksDB Yes Yes Yes No No N/A

Benchmark results

For this benchmark we tested the put, get, and "havekey" routines for databases that meet the criteria of being multi-process. Tests were performed for other transaction modes besides "WAL" for Sqlite, but WAL was by far the fastest of all the options. "SqlLiteScalar" is a variant of the SqlLite tests that uses tables with multiple columns instead of treating the database purely as a key value store. Keys in this example were 9 bytes long (common for our usecase) and values were 128 bytes long. There was no significant performance differences using 9 bytes or 1028 byte values

Method Type Mean Error StdDev Gen0 Gen1 Gen2 Allocated
Put FileSystem 125,418.1 ns 2,340.78 ns 2,403.80 ns 0.2441 - - 5176 B
Get FileSystem 29,349.1 ns 581.06 ns 543.52 ns 0.3357 - - 5752 B
HaveKey FileSystem 11,911.0 ns 230.37 ns 226.26 ns 0.0458 - - 824 B
Put LiteDB 1,933,521.3 ns 38,290.43 ns 83,240.25 ns 29.2969 29.2969 29.2969 163360 B
Get LiteDB 309,517.3 ns 6,185.27 ns 8,466.46 ns 30.7617 30.7617 30.7617 148657 B
HaveKey LiteDB 317,962.0 ns 6,273.28 ns 13,503.90 ns 30.7617 30.7617 30.7617 156145 B
Put LMDB 525,621.3 ns 10,040.93 ns 12,331.17 ns - - - 593 B
Get LMDB 872.0 ns 17.33 ns 29.42 ns 0.0439 - - 744 B
HaveKey LMDB 835.6 ns 13.55 ns 12.68 ns 0.0353 - - 592 B
Put Sqlite_WAL 7,169.4 ns 120.46 ns 112.68 ns 0.1602 - - 2696 B
Get Sqlite_WAL 5,484.1 ns 94.44 ns 88.34 ns 0.4578 - - 7688 B
HaveKey Sqlite_WAL 4,715.3 ns 92.07 ns 98.51 ns 0.1450 - - 2448 B
Put Sqlite_Scalar 14,251.8 ns 263.21 ns 246.21 ns 0.4425 - - 7544 B
Get Sqlite_Scalar 8,571.2 ns 169.00 ns 187.84 ns 0.5493 - - 9336 B
HaveKey Sqlite_Scalar 4,714.2 ns 91.73 ns 90.09 ns 0.1450 - - 2448 B

Decision Outcome

Sqlite with WAL has the best balanced performance, while also allowing for more advanced features like secondary indexes. In addition there are a lot of tools available for working with Sqlite databases which could help with debugging and interop with other tools.