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chore(core): reduce sequencer txn log file storage record length from 60 to 40 bytes #4322

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chore(core): reduce sequencer txn log file storage record length from 60 to 40 bytes #4322

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@ideoma ideoma commented Mar 21, 2024

The new sequencer V2 record can be compacted to 40 bytes instead of 60 without sacrificing too much of usable data range and code complexity.

Proposed layout:

  • Structure Version: 40 bits, range: 0-1T
  • WAL Id: 32 bits, range: 0-4B (unchanged)
  • Segment Txn: 24 bits, range: 0-16M
  • Segment Id: 24 bits, range: 0-16M
  • Commit Timestamp: 48 bits, stored in milliseconds, range: years 1970-10889
  • Min Data Timestamp: 64 bits, microseconds
  • Max Data Timestamp: 48 bits, stored as the difference from Min Data Timestamp, microseconds. Range: 3 years from Min Data Timestamp
  • Commit Row Count: 40 bits, range: 0-1T

@ideoma ideoma marked this pull request as draft March 21, 2024 13:36
@ideoma ideoma marked this pull request as ready for review April 16, 2024 08:27
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ideoma commented Apr 29, 2024

[PR Coverage check]

😍 pass : 52 / 64 (81.25%)

file detail

path covered line new line coverage
🔵 io/questdb/cairo/wal/seq/TableSequencerImpl.java 1 4 25.00%
🔵 io/questdb/cairo/wal/WalWriter.java 8 14 57.14%
🔵 io/questdb/cairo/wal/seq/TableTransactionLogV2.java 39 42 92.86%
🔵 io/questdb/cairo/wal/WalUtils.java 1 1 100.00%
🔵 io/questdb/cairo/wal/seq/TableTransactionLogV1.java 3 3 100.00%

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