253 lines
7.0 KiB
Markdown
253 lines
7.0 KiB
Markdown
# Tantivy Full‑Text Backend (JSON‑RPC)
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This document explains how to use HeroDB’s Tantivy-backed full‑text search as a dedicated database backend and provides copy‑pasteable JSON‑RPC requests. Tantivy is available only for non‑admin databases (db_id >= 1). Admin DB 0 always uses Redb/Sled and rejects FT operations.
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Important characteristics:
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- Tantivy is a third backend alongside Redb and Sled. It provides search indexes only; there is no KV store backing it.
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- On Tantivy databases, Redis KV/list/hash commands are rejected; only FT commands and basic control (SELECT, CLIENT, INFO, etc.) are allowed.
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- FT JSON‑RPC is namespaced as "herodb" and methods are named with underscore: herodb_ftCreate, herodb_ftAdd, herodb_ftSearch, herodb_ftDel, herodb_ftInfo, herodb_ftDrop.
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Reference to server implementation:
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- RPC methods are defined in [rust.trait Rpc()](src/rpc.rs:70):
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- [rust.fn ft_create()](src/rpc.rs:121)
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- [rust.fn ft_add()](src/rpc.rs:130)
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- [rust.fn ft_search()](src/rpc.rs:141)
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- [rust.fn ft_del()](src/rpc.rs:154)
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- [rust.fn ft_info()](src/rpc.rs:158)
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- [rust.fn ft_drop()](src/rpc.rs:162)
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Notes on responses:
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- ftCreate/ftAdd/ftDel/ftDrop return a JSON boolean: true on success.
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- ftSearch/ftInfo return a JSON object with a single key "resp" containing a RESP‑encoded string (wire format used by Redis). You can display or parse it on the client side as needed.
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RESP usage (redis-cli):
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- For RESP clients, you must SELECT the Tantivy database first. SELECT now succeeds for Tantivy DBs without opening KV storage.
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- After SELECT, you can run FT.* commands within that DB context.
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Example with redis-cli:
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```bash
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# Connect to server
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redis-cli -p 6379
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# Select Tantivy DB 1 (public by default)
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SELECT 1
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# → OK
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# Create index
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FT.CREATE product_catalog SCHEMA title TEXT description TEXT category TAG price NUMERIC rating NUMERIC location GEO
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# → OK
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# Add a document
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FT.ADD product_catalog product:1 1.0 title "Wireless Bluetooth Headphones" description "Premium noise-canceling headphones with 30-hour battery life" category "electronics,audio" price 299.99 rating 4.5 location "-122.4194,37.7749"
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# → OK
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# Search
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FT.SEARCH product_catalog wireless LIMIT 0 3
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# → RESP array with hits
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```
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Storage layout (on disk):
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- Indices are stored per database under:
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- <base_dir>/search_indexes/<db_id>/<index_name>
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- Example: /tmp/test/search_indexes/1/product_catalog
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0) Create a new Tantivy database
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Use herodb_createDatabase with backend "Tantivy". DB 0 cannot be Tantivy.
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```json
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{
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"jsonrpc": "2.0",
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"id": 1,
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"method": "herodb_createDatabase",
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"params": [
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"Tantivy",
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{ "name": "search-db", "storage_path": null, "max_size": null, "redis_version": null },
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null
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]
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}
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```
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The response contains the allocated db_id (>= 1). Use that id in the calls below.
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1) FT.CREATE — create an index with schema
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Method: herodb_ftCreate → [rust.fn ft_create()](src/rpc.rs:121)
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Schema format is an array of tuples: [ [field_name, field_type, [options...] ], ... ]
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Supported field types: "TEXT", "NUMERIC" (defaults to F64), "TAG", "GEO"
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Supported options (subset): "WEIGHT", "SORTABLE", "NOINDEX", "SEPARATOR", "CASESENSITIVE"
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```json
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{
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"jsonrpc": "2.0",
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"id": 2,
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"method": "herodb_ftCreate",
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"params": [
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1,
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"product_catalog",
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[
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["title", "TEXT", ["SORTABLE"]],
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["description", "TEXT", []],
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["category", "TAG", ["SEPARATOR", ","]],
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["price", "NUMERIC", ["SORTABLE"]],
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["rating", "NUMERIC", []],
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["location", "GEO", []]
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]
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]
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}
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```
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Returns: true on success.
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2) FT.ADD — add or replace a document
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Method: herodb_ftAdd → [rust.fn ft_add()](src/rpc.rs:130)
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Fields is an object (map) of field_name → value (all values are sent as strings). GEO expects "lat,lon".
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```json
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{
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"jsonrpc": "2.0",
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"id": 3,
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"method": "herodb_ftAdd",
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"params": [
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1,
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"product_catalog",
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"product:1",
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1.0,
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{
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"title": "Wireless Bluetooth Headphones",
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"description": "Premium noise-canceling headphones with 30-hour battery life",
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"category": "electronics,audio",
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"price": "299.99",
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"rating": "4.5",
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"location": "-122.4194,37.7749"
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}
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]
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}
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```
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Returns: true on success.
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3) FT.SEARCH — query an index
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Method: herodb_ftSearch → [rust.fn ft_search()](src/rpc.rs:141)
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Parameters: (db_id, index_name, query, filters?, limit?, offset?, return_fields?)
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- filters: array of [field, value] pairs (Equals filter)
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- limit/offset: numbers (defaults: limit=10, offset=0)
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- return_fields: array of field names to include (optional)
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Simple query:
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```json
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{
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"jsonrpc": "2.0",
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"id": 4,
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"method": "herodb_ftSearch",
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"params": [1, "product_catalog", "wireless", null, 10, 0, null]
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}
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```
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Pagination + filters + selected fields:
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```json
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{
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"jsonrpc": "2.0",
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"id": 5,
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"method": "herodb_ftSearch",
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"params": [
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1,
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"product_catalog",
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"mouse",
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[["category", "electronics"]],
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5,
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0,
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["title", "price", "rating"]
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]
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}
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```
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Response shape:
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```json
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{
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"jsonrpc": "2.0",
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"id": 5,
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"result": { "resp": "*...RESP encoded array..." }
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}
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```
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4) FT.INFO — index metadata
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Method: herodb_ftInfo → [rust.fn ft_info()](src/rpc.rs:158)
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```json
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{
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"jsonrpc": "2.0",
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"id": 6,
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"method": "herodb_ftInfo",
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"params": [1, "product_catalog"]
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}
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```
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Response shape:
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```json
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{
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"jsonrpc": "2.0",
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"id": 6,
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"result": { "resp": "*...RESP encoded array with fields and counts..." }
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}
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```
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5) FT.DEL — delete by doc id
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Method: herodb_ftDel → [rust.fn ft_del()](src/rpc.rs:154)
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```json
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{
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"jsonrpc": "2.0",
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"id": 7,
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"method": "herodb_ftDel",
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"params": [1, "product_catalog", "product:1"]
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}
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```
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Returns: true on success. Note: current implementation logs and returns success; physical delete may be a no‑op until delete is finalized in the engine.
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6) FT.DROP — drop an index
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Method: herodb_ftDrop → [rust.fn ft_drop()](src/rpc.rs:162)
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```json
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{
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"jsonrpc": "2.0",
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"id": 8,
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"method": "herodb_ftDrop",
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"params": [1, "product_catalog"]
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}
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```
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Returns: true on success.
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Field types and options
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- TEXT: stored/indexed/tokenized text. "SORTABLE" marks it fast (stored + fast path in our wrapper).
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- NUMERIC: stored/indexed numeric; default precision F64. "SORTABLE" enables fast column.
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- TAG: exact matching terms. Options: "SEPARATOR" (default ","), "CASESENSITIVE" (default false).
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- GEO: "lat,lon" string; stored as two numeric fields internally.
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Backend and permission gating
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- FT methods are rejected on DB 0.
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- FT methods require the database backend to be Tantivy; otherwise RPC returns an error.
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- Write‑like FT methods (create/add/del/drop) follow the same permission model as Redis writes on selected databases.
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Troubleshooting
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- "DB backend is not Tantivy": ensure the database was created with backend "Tantivy".
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- "FT not allowed on DB 0": use a non‑admin database id (>= 1).
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- Empty search results: confirm that the queried fields are tokenized/indexed (TEXT) and that documents were added successfully.
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Related docs
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- Command‑level search overview: [docs/search.md](docs/search.md:1)
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- RPC definitions: [src/rpc.rs](src/rpc.rs:1) |