From b04bcb5b0cf8dc4164419f5a7421cbad94087fe4 Mon Sep 17 00:00:00 2001
From: Philipinho <16838612+Philipinho@users.noreply.github.com>
Date: Thu, 23 Apr 2026 15:52:35 +0100
Subject: [PATCH] feat(base): env var for duckdb reader-pool size

---
 .../core/base/query-cache/query-cache.config.ts  |  2 ++
 .../environment/environment.service.ts           | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/apps/server/src/core/base/query-cache/query-cache.config.ts b/apps/server/src/core/base/query-cache/query-cache.config.ts
index 44b7d3f5..1f0dd3af 100644
--- a/apps/server/src/core/base/query-cache/query-cache.config.ts
+++ b/apps/server/src/core/base/query-cache/query-cache.config.ts
@@ -10,6 +10,7 @@ export type QueryCacheConfig = {
   threads: number;
   trace: boolean;
   tempDirectory: string;
+  readerPoolSize: number;
 };
 
 @Injectable()
@@ -25,6 +26,7 @@ export class QueryCacheConfigProvider {
       threads: env.getBaseQueryCacheThreads(),
       trace: env.getBaseQueryCacheTrace(),
       tempDirectory: env.getBaseQueryCacheTempDirectory(),
+      readerPoolSize: env.getBaseQueryCacheReaderPoolSize(),
     };
   }
 }
diff --git a/apps/server/src/integrations/environment/environment.service.ts b/apps/server/src/integrations/environment/environment.service.ts
index 3ef0b95b..74ef4d8e 100644
--- a/apps/server/src/integrations/environment/environment.service.ts
+++ b/apps/server/src/integrations/environment/environment.service.ts
@@ -385,4 +385,20 @@ export class EnvironmentService {
       10,
     );
   }
+
+  getBaseQueryCacheReaderPoolSize(): number {
+    // Number of reader connections held open against the shared DuckDB
+    // instance. Reads are dispatched via `withReader()` which checks out a
+    // connection, runs the query, returns it. Bigger pool = more concurrent
+    // reads without serialization, at the cost of per-connection overhead
+    // (each connection carries its own catalog snapshot + prepared-statement
+    // cache ~= 300 KB).
+    //
+    // Default 4 matches libuv's default thread-pool size. Raise to 8+ if
+    // you see p99 list latency correlate with concurrent request volume.
+    return parseInt(
+      this.configService.get<string>('BASE_QUERY_CACHE_READER_POOL_SIZE', '4'),
+      10,
+    );
+  }
 }