Fix RocksDB: Blob garbage collection rewrites every stored blob on each compaction of the blobs column family, about once per 128MB of new mail

Author: mdecimus

CHANGELOG.md

@@ -12,6 +12,7 @@ If you are upgrading from v0.16.x, replace the binary (or run `docker pull`). If
 ## Changed
 
 ## Fixed
+- RocksDB: Blob garbage collection rewrites every stored blob on each compaction of the blobs column family, about once per 128MB of new mail.
 
 ## [0.16.25] - 2026-10-05
 

crates/store/src/backend/rocksdb/main.rs

@@ -72,9 +72,8 @@ impl RocksDbStore {
         let mut cf_opts = cf_options(CfProfile::Blob, &cache, write_buffer_size);
         cf_opts.set_enable_blob_files(true);
         cf_opts.set_min_blob_size(config.blob_size);
-        cf_opts.set_enable_blob_gc(true);
+        cf_opts.set_enable_blob_gc(false);
         cf_opts.set_blob_gc_age_cutoff(1.0);
-        cf_opts.set_blob_gc_force_threshold(0.5);
         cfs.push(ColumnFamilyDescriptor::new(CF_BLOBS, cf_opts));
 
         // Other cfs

crates/store/src/backend/rocksdb/write.rs

@@ -6,8 +6,8 @@
 
 use super::{CF_INDEXES, CF_LOGS, CfHandle, RocksDbStore, into_error};
 use crate::{
-    Deserialize, IndexKey, Key, LogKey, SUBSPACE_COUNTER, SUBSPACE_IN_MEMORY_COUNTER,
-    SUBSPACE_QUOTA,
+    Deserialize, IndexKey, Key, LogKey, SUBSPACE_BLOBS, SUBSPACE_COUNTER,
+    SUBSPACE_IN_MEMORY_COUNTER, SUBSPACE_QUOTA,
     backend::deserialize_i64_le,
     write::{
         AssignedIds, Batch, MAX_COMMIT_ATTEMPTS, MAX_COMMIT_TIME, MergeResult, Operation,
@@ -16,15 +16,18 @@ use crate::{
 };
 use rand::RngExt;
 use rocksdb::{
-    BoundColumnFamily, ErrorKind, IteratorMode, OptimisticTransactionDB,
-    OptimisticTransactionOptions, WriteOptions,
+    BottommostLevelCompaction, BoundColumnFamily, CompactOptions, ErrorKind, IteratorMode,
+    OptimisticTransactionDB, OptimisticTransactionOptions, WriteOptions,
 };
 use std::{
     sync::Arc,
     thread::sleep,
     time::{Duration, Instant},
 };
 
+const BLOB_GC_MIN_GARBAGE: u64 = 256 * 1024 * 1024;
+const BLOB_GC_GARBAGE_RATIO: f64 = 0.25;
+
 impl RocksDbStore {
     pub(crate) async fn write(&self, mut batch: Batch<'_>) -> trc::Result<AssignedIds> {
         let db = self.db.clone();
@@ -114,6 +117,28 @@ impl RocksDbStore {
                 }
             }
 
+            let cf = db.subspace_handle(SUBSPACE_BLOBS);
+            let total = db
+                .property_int_value_cf(&cf, "rocksdb.live-blob-file-size")
+                .map_err(into_error)?
+                .unwrap_or_default();
+            let garbage = db
+                .property_int_value_cf(&cf, "rocksdb.live-blob-file-garbage-size")
+                .map_err(into_error)?
+                .unwrap_or_default();
+
+            if garbage >= BLOB_GC_MIN_GARBAGE
+                && garbage as f64 >= total as f64 * BLOB_GC_GARBAGE_RATIO
+            {
+                db.set_options_cf(&cf, &[("enable_blob_garbage_collection", "true")])
+                    .map_err(into_error)?;
+                let mut opts = CompactOptions::default();
+                opts.set_bottommost_level_compaction(BottommostLevelCompaction::Force);
+                db.compact_range_cf_opt(&cf, None::<&[u8]>, None::<&[u8]>, &opts);
+                db.set_options_cf(&cf, &[("enable_blob_garbage_collection", "false")])
+                    .map_err(into_error)?;
+            }
+
             Ok(())
         })
         .await