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oc/memory/pitfalls/sqlite-cjk-tokenizer.md
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xiaoshuai a64ea2acb3 Add memory plugin: three-tier markdown store with plugin-driven retrieval
A durable memory layer for OpenCode. Structure:

  ROOT.md          total plan: goals, hard rules, directory registry,
                   and a scenario -> file routing table
  <category>/
    index.md       one line per file, COMPILED from frontmatter
    <slug>.md      the memory itself

Two roots, same shape: <config>/memory/ (global) and
<project canonical>/.memory/ (project). Project wins on conflict; global
hard rules stay resident everywhere.

Why a plugin rather than a skill that tells the model to read a folder:
model-driven retrieval is unreliable — the model forgets, reads half the
files, or reads the wrong ones. Markdown is the human-facing format; the
plugin is the engine that parses, scores, and injects.

Measured, not assumed: FTS5's two built-in tokenizers both fail on this
corpus. On SQLite 3.53.4 with "部署脚本用 pnpm 而不是 npm...": unicode61
emits 7 terms for the whole sentence and matches 0 hits for "部署";
trigram needs >= 3 characters and also returns 0 for that two-character
word. So tokenization happens in the plugin (CJK bigrams, latin words)
and no SQL index is used — a thousand memories are fine to scan.

index.md and ROOT's two tables are compiled, never hand-edited: a
hand-maintained index drifts, a generated one cannot. Hit counters live
in .state.json so cross-device sync does not conflict on every recall.

Tools are named recall/remember/forget/inspect rather than
write/read/status: generic names were observed shadowing the harness's
own built-in tools.
2026-10-09 10:17:45 +08:00

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---
id: pitfalls/sqlite-cjk-tokenizer.md
kind: fact
summary: unicode61 把整段中文当一个 token,trigram 漏掉两字词,必须自己分词。
highlight: 实测:unicode61 查"部署"=0 命中;trigram 查"部署"=0 命中(需≥3字符)
created: 1791512161994
updated: 1791512161994
load_when:
- SQLite
- FTS5
- 全文检索
- 分词
- 中文检索
---
在 SQLite 3.53.4 上实测,字符串「部署脚本用 pnpm 而不是 npm,因为 lockfile 不兼容」:
- `unicode61`(FTS5 默认)把 `部署脚本用` 当作**一个 token**,整句只产生 7 个词条。查「部署」0 命中,查「部署脚本」也 0 命中。子串永远匹配不上。
- `trigram` 要求查询 ≥3 字符。词表是「不兼」「而不」「m,因」这种三字滑窗。查「部署」0 命中,查「部署脚」1 命中。
中文里「部署」「配置」「依赖」「接口」这类**两字词占比极高**,trigram 漏掉的正好是最常用的一批。
解法:索引前自己切 CJK 字符二元组,拉丁走 porter 词干,FTS5 只当倒排索引用。