tree bc5997eced67d5f6680485e7ec0327582f3a17c0
parent 31601eee4a6d63e11abd9c7bc30f2f37ae93860d
author CritasWang <critas@outlook.com> 1784098492 +0800
committer GitHub <noreply@github.com> 1784098492 +0800
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perf: single-pass single-buffer tablet serialization, BigInt-free int64 writes (#16)

CPU profiling of the write path (insertTablet-heavy workload) showed the
event loop 79.5% busy with serializeTabletValues at 26% self time and GC
at 24.5% — almost entirely allocation churn in the serializer. This
rewrites the fast (default) write path:

- serializeTabletValues: new single-pass serializeTabletValuesFast()
  writes all columns AND null bitmaps into ONE exactly-sized buffer.
  Eliminates the rows->columns transpose (one array per column), the
  per-column boolean[] null bitmaps (built then discarded when a column
  has no nulls), the per-column intermediate buffers, the per-column
  1-byte Buffer.from([flag]) allocations, and the trailing Buffer.concat
  (which re-copied the whole payload). Fixed-width sizes come from the
  schema; variable-width columns get one byteLength pre-scan.
- INT64/TIMESTAMP writes: writeBigInt64BE(BigInt(v)) replaced with a
  sign-correct hi/lo 32-bit pair (hi = floor(v / 2^32), lo = v >>> 0),
  avoiding one BigInt allocation per value. BigInt inputs and non-safe
  integers still take the exact writeBigInt64BE path.
- TEXT/STRING columns: single-entry encode cache — TAG columns repeat
  one string per tablet, so consecutive identical values reuse the
  encoded Buffer instead of re-encoding UTF-8 every row.
- BufferPool: removed from the write path. It was acquire-only (zero
  release() calls anywhere in src/), i.e. a guaranteed 0% hit rate and
  pure overhead over Buffer.allocUnsafe. The class stays exported
  (public API) but is deprecated.

Wire format is unchanged — existing serialization unit tests pass
untouched, and new golden tests assert the fast path output equals the
legacy path byte-for-byte for mixed-type tablets with nulls, all-null
columns, bitmap-width edge cases (17 rows), BLOB/DATE, and negative /
MIN_SAFE_INTEGER / BigInt int64 values. The legacy path
(enableFastSerialization=false) is untouched.