fix: MVStore.compact: run map copy in parallel by default (¼ cores, override via h2.compactThreads)

naive924 · naive924 · commit 858e74abc367 · 2025-09-03T15:58:49.000+09:00
diff --git a/h2/src/main/org/h2/mvstore/MVStore.java b/h2/src/main/org/h2/mvstore/MVStore.java
@@ -408,7 +408,7 @@ private static void compact(MVStore source, MVStore target) {
                 }
             }
 
-            int poolSize = Integer.getInteger("h2.compactThreads", 1);
+            int poolSize = Integer.getInteger("h2.compactThreads", Math.max(1, Runtime.getRuntime().availableProcessors() / 4));
             ExecutorService pool = Executors.newFixedThreadPool(poolSize);
             CompletableFuture.allOf(
                 // We are going to cheat a little bit in the copyFrom() by employing "incomplete" pages,

Original file line number	Diff line number	Diff line change
`@@ -408,7 +408,7 @@ private static void compact(MVStore source, MVStore target) {`
`408`	`408`	`}`
`409`	`409`	`}`
`410`	`410`
`411`		`- int poolSize = Integer.getInteger("h2.compactThreads", 1);`
	`411`	`+ int poolSize = Integer.getInteger("h2.compactThreads", Math.max(1, Runtime.getRuntime().availableProcessors() / 4));`
`412`	`412`	`ExecutorService pool = Executors.newFixedThreadPool(poolSize);`
`413`	`413`	`CompletableFuture.allOf(`
`414`	`414`	`// We are going to cheat a little bit in the copyFrom() by employing "incomplete" pages,`