From fd7d53ba4198083749dafb852c33285a64db1270 Mon Sep 17 00:00:00 2001
From: dawn <90008@klbr.net>
Date: Sun, 12 Jul 2026 22:01:10 +0300
Subject: [PATCH] [db] compress L0 for monotonic-key keyspaces

monotonic {seq}/{id}/{time_us}|{id} keys make every l0 flush disjoint, so
lsm-tree leveled compaction trivial-moves segments down without rewriting.
the l0 compression+block-size slot is therefore permanent for relay_events,
events, and jetstream_events -- with l0=none they were stored uncompressed
forever and the l1+ zstd policy was dead code (prod relay: btrfs reclaiming
1.55x on 155/157g of raw relay_events).

set l0 compression to zstd:3 and l0 block size to 128kib (matching btrfs's
128k compression window so ratio reaches parity) on the non-ephemeral paths.
newest events are still served uncompressed from the memtable; only flushed
historical segments (read on cursor replay) pay decompress. also give
relay_events its own dict lookup key instead of borrowing the nonexistent
'events' key in relay mode.
---
 src/db/schema.rs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/db/schema.rs b/src/db/schema.rs
index eee48ae..9c385d0 100644
--- a/src/db/schema.rs
+++ b/src/db/schema.rs
@@ -522,9 +522,10 @@ impl Schema for Events {
                 cx.cfg
                     .ephemeral
                     .then(|| BlockSizePolicy::new([kb(64), kb(128), kb(256)]))
-                    .unwrap_or_else(|| BlockSizePolicy::new([kb(16), kb(64)])),
+                    .unwrap_or_else(|| BlockSizePolicy::new([kb(128), kb(256)])),
             )
-            // we are streaming the new events to consumers so we dont want to compress them
+            // monotonic {ID} keys are trivial-moved down (never rewritten), so the L0
+            // policy is permanent; the live tail is served uncompressed from the memtable
             .data_block_compression_policy(
                 cx.cfg
                     .ephemeral
@@ -536,7 +537,7 @@ impl Schema for Events {
                     })
                     .unwrap_or_else(|| {
                         CompressionPolicy::new([
-                            CompressionType::None,
+                            (cx.compression)("events", 3),
                             (cx.compression)("events", 3),
                             (cx.compression)("events", 3),
                             (cx.compression)("events", 5),
@@ -583,9 +584,9 @@ impl Schema for JetstreamEvents {
             // time-ordered append-only stream metadata, only iterated for replay.
             .expect_point_read_hits(true)
             .max_memtable_size(mb(cx.cfg.db_events_memtable_size_mb))
-            .data_block_size_policy(BlockSizePolicy::new([kb(16), kb(64), kb(128)]))
+            .data_block_size_policy(BlockSizePolicy::new([kb(128), kb(256)]))
             .data_block_compression_policy(CompressionPolicy::new([
-                CompressionType::None,
+                (cx.compression)("jetstream_events", 3),
                 (cx.compression)("jetstream_events", 3),
                 (cx.compression)("jetstream_events", 5),
             ]))
@@ -615,12 +616,14 @@ impl Schema for RelayEvents {
             // only iterated for cursor replay
             .expect_point_read_hits(true)
             .max_memtable_size(mb(cx.cfg.db_events_memtable_size_mb))
-            .data_block_size_policy(BlockSizePolicy::new([kb(64), kb(128), kb(256)]))
+            .data_block_size_policy(BlockSizePolicy::new([kb(128), kb(256)]))
+            // monotonic {SEQ} keys are trivial-moved down (never rewritten), so L0
+            // compression is permanent; the live tail is served from the memtable
             .data_block_compression_policy(CompressionPolicy::new([
-                CompressionType::None,
-                (cx.compression)("events", 3),
-                (cx.compression)("events", 3),
-                (cx.compression)("events", 5),
+                (cx.compression)("relay_events", 3),
+                (cx.compression)("relay_events", 3),
+                (cx.compression)("relay_events", 3),
+                (cx.compression)("relay_events", 5),
             ]))
             .data_block_restart_interval_policy(RestartIntervalPolicy::new([64, 128]))
     }
-- 
2.51.2