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- Pure Nim wire protocol client (async + sync, no C FFI) - Query Builder: fluent API, SQL generator, execution, transactions - Schema Builder: create/alter/drop tables, column operations - Connection pool with aging and timeout handling - ORM integration via compile-time DB_BARADB switch - Tests: test_open, test_query - Documentation: README.md, PLAN_BARADB.md
78 lines
2.3 KiB
Markdown
78 lines
2.3 KiB
Markdown
Example: Prepared Statement for SurrealDB
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===
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> [!WARNING]
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> SurrealDB の prepared statement は server-side prepare ではなく、client-side template reuse と `/sql` の multi-statement 実行で再現しています。
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[back](../../README.md)
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## index
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<!--ts-->
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* [Example: Prepared Statement for SurrealDB](#example-prepared-statement-for-surrealdb)
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* [index](#index)
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* [About](#about)
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* [Create Connection](#create-connection)
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* [prepare](#prepare)
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* [withConn](#withconn)
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* [Cache Control](#cache-control)
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<!--te-->
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---
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## About
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[SurrealDB official docs](https://surrealdb.com/docs)
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Prepared statement の公開 API は他 driver に寄せていますが、SurrealDB では内部的に次の形へ展開します。
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```sql
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LET $a = "user:alice";
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SELECT * FROM "user" WHERE "id" = $a;
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```
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`?` は `$a`, `$b`, ... に変換され、引数は `LET` で前置されます。これにより、1 リクエストで安全に再利用できるテンプレートとして扱えます。
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## Create Connection
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```nim
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import std/asyncdispatch
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import allographer/connection
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let surreal = dbOpen(SurrealDB, "test", "test", "user", "pass", "http://surreal", 8000, 5, 30, false, false).await
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```
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## prepare
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```nim
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import std/asyncdispatch
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import std/json
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import allographer/query_builder
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let stmt = surreal.prepare("""SELECT * FROM "user" WHERE "id" = ?""")
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let rows = await stmt.get(@["user:alice"])
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let row = await stmt.first(@["user:alice"])
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await stmt.exec(@["user:alice"])
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await stmt.close()
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```
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`close()` は logical close です。SurrealDB 側に物理 prepared handle はないため、キャッシュの整理は `flushStmt()` / `clearStmtCache()` で行います。
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## withConn
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```nim
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await surreal.withConn(
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proc(ctx: SurrealPreparedContext): Future[void] {.async.} =
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discard await stmt.first(ctx, @["user:alice"])
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await stmt.exec(ctx, @["user:alice"])
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)
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```
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`withConn()` は同じ connection index を使い回したいときの API です。将来の session 前提最適化や transaction helper とも相性がよい形にしてあります。
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## Cache Control
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```nim
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await surreal.flushStmt(stmt)
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await surreal.clearStmtCache()
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```
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`flushStmt(stmt)` はその prepared statement を閉じて、対応するテンプレートをキャッシュから外します。`clearStmtCache()` はキャッシュ全体を空にします。
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