84 lines
3.2 KiB
Markdown
84 lines
3.2 KiB
Markdown
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# M8.2 — Dual-write indexing pipeline
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| Field | Value |
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|---|---|
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| Phase | M8 — Hybrid Search |
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| Size | M — 1–2 days |
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| Status | ⬜ |
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| Flags | — |
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| Spec | inlined below |
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| Blocks | M8.4, M8.5 |
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| Depends | M8.1 (OpenSearch running), M2.4 (pgvector repo) |
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## Goal
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When a document is ingested, write to **both** pgvector (embedding) and OpenSearch (raw text) atomically. Same `chunk_id` in both stores. If one write fails, log error but don't block the other — eventual consistency, not transactions.
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## Design
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**Unified ID mapping:** Both stores use the same `chunk_id` (UUID). The ingest worker generates the ID once, writes to both.
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**Chunking policy:** 512-token chunks with 10% (51-token) overlap. Deterministic — same input always produces same chunks with same IDs.
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**Dual write sequence:**
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1. Chunk document (heading-boundary or fixed-size).
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2. Generate embedding via LLM.
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3. Write to pgvector: `INSERT INTO chunks (id, embedding, text, source, project, level, breadcrumb)`.
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4. Write to OpenSearch: `PUT vault-{project}/_doc/{chunk_id}` with `{content, source, level, breadcrumb, project_id, indexed_at}`.
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5. If OpenSearch write fails: log warning, mark chunk as `opensearch_pending=true` in pgvector. Background retry later.
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**OpenSearch index mapping:**
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```json
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{
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"content": {"type": "text", "analyzer": "standard", "boost": 2.0},
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"section_title": {"type": "text", "boost": 1.5},
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"breadcrumb": {"type": "keyword"},
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"source": {"type": "keyword"},
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"project_id": {"type": "keyword"},
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"level": {"type": "keyword"},
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"indexed_at": {"type": "date"}
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}
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```
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**Deduplication:** Before writing, check `chunk_hash` (SHA256 of text). If hash exists and `is_indexed=true` in both stores, skip.
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## Steps
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1. Add `opensearch_pending` boolean column to `chunks` table (migration).
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2. Update `IngestWorker::process_ingest()` to call OpenSearch after pgvector write.
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3. Make `OpenSearchClient::index_document()` public, fix method signature.
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4. Add background task: retry `opensearch_pending=true` chunks every 5 minutes.
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5. Add dedup check before dual write.
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## Acceptance
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1. `mem ingest --dry-run` on a test doc shows chunks written to both stores.
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2. Same `chunk_id` exists in both `SELECT id FROM chunks` and `GET vault-*/_doc/{id}`.
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3. Kill OpenSearch mid-ingest: pgvector write succeeds, chunk marked `opensearch_pending=true`.
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4. Restart OpenSearch: background retry picks up pending chunks within 5 minutes.
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5. Re-ingest same document: dedup skips already-indexed chunks (0 new writes).
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## Verify
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```bash
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# Ingest a test document
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cargo run -- ingest --project test --source fixtures/refcorpus/small.md
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# Check pgvector
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psql -c "SELECT id, source, opensearch_pending FROM chunks WHERE project='test'"
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# Check OpenSearch
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curl -k -H "Authorization: Bearer $TOKEN" \
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https://opensearch-internal:9200/vault-test/_search | jq '.hits.total'
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# IDs must match
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```
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**False pass:** Both stores have data but with different IDs — the join on `chunk_id` finds zero matches. Assert `SELECT count(*) FROM chunks WHERE id IN (opensearch_ids)` equals total indexed.
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## Artifacts
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- Modified `crates/mem-cli/src/ingest_worker.rs`
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- Modified `crates/mem-store/src/lib.rs` (migration)
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- Modified `crates/mem-cli/src/opensearch_client.rs`
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