From a9a9a8993bf01f24eb9542454dddd62fdd0bab3e Mon Sep 17 00:00:00 2001
From: Clement Rey <cr.rey.clement@gmail.com>
Date: Fri, 10 Mar 2023 17:23:59 +0100
Subject: [PATCH 1/2] add trace log to datastore GC

---
 crates/re_arrow_store/src/store_gc.rs | 35 ++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/crates/re_arrow_store/src/store_gc.rs b/crates/re_arrow_store/src/store_gc.rs
index cc3fbc50ad66..19d6020fe390 100644
--- a/crates/re_arrow_store/src/store_gc.rs
+++ b/crates/re_arrow_store/src/store_gc.rs
@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 
 use arrow2::array::{Array, ListArray};
-use re_log::info;
+use re_log::{info, trace};
 use re_log_types::{ComponentName, TimeRange, Timeline};
 
 use crate::{ComponentBucket, DataStore};
@@ -110,6 +110,7 @@ impl DataStore {
     ) -> Vec<Box<dyn Array>> {
         let mut dropped = Vec::<Box<dyn Array>>::new();
 
+        let mut i = 0usize;
         while drop_at_least_size_bytes > 0.0 {
             // Find and drop the earliest (in terms of _insertion order_) primary component bucket
             // that we can find.
@@ -119,11 +120,31 @@ impl DataStore {
                 .and_then(|table| (table.buckets.len() > 1).then(|| table.buckets.pop_front()))
                 .flatten()
             else {
+                trace!(
+                    kind = "gc",
+                    id = self.gc_id,
+                    timeline = %primary_timeline.name(),
+                    %primary_component,
+                    iter = i,
+                    remaining = re_format::format_bytes(drop_at_least_size_bytes),
+                    "no more primary buckets, giving up"
+                );
                 break;
             };
 
             drop_at_least_size_bytes -= primary_bucket.total_size_bytes() as f64;
 
+            trace!(
+                kind = "gc",
+                id = self.gc_id,
+                timeline = %primary_timeline.name(),
+                %primary_component,
+                iter = i,
+                reclaimed = re_format::format_bytes(primary_bucket.total_size_bytes() as f64),
+                remaining = re_format::format_bytes(drop_at_least_size_bytes),
+                "found & dropped primary component bucket"
+            );
+
             // From there, find and drop all component buckets (in _insertion order_) that do not
             // contain any data more recent than the time range covered by the primary
             // component bucket (for the primary timeline!).
@@ -137,10 +158,22 @@ impl DataStore {
                     if primary_bucket.encompasses(primary_timeline, &bucket.time_ranges) {
                         let bucket = table.buckets.pop_front().unwrap();
                         drop_at_least_size_bytes -= bucket.total_size_bytes() as f64;
+                        trace!(
+                            kind = "gc",
+                            id = self.gc_id,
+                            timeline = %primary_timeline.name(),
+                            %primary_component,
+                            iter = i,
+                            reclaimed = re_format::format_bytes(bucket.total_size_bytes() as f64),
+                            remaining = re_format::format_bytes(drop_at_least_size_bytes),
+                            "found & dropped secondary component bucket"
+                        );
                     } else {
                         break;
                     }
                 }
+
+                i += 1;
             }
 
             // We don't collect indices: they behave as tombstones.

From f0c0e4e71630ba1aff69a78c8813a79f04495aa1 Mon Sep 17 00:00:00 2001
From: Clement Rey <cr.rey.clement@gmail.com>
Date: Fri, 10 Mar 2023 17:24:34 +0100
Subject: [PATCH 2/2] update logdb defaults

---
 crates/re_data_store/src/log_db.rs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/crates/re_data_store/src/log_db.rs b/crates/re_data_store/src/log_db.rs
index 27d1762459f4..ac7b5d6db37d 100644
--- a/crates/re_data_store/src/log_db.rs
+++ b/crates/re_data_store/src/log_db.rs
@@ -37,11 +37,21 @@ impl Default for EntityDb {
             data_store: re_arrow_store::DataStore::new(
                 InstanceKey::name(),
                 DataStoreConfig {
-                    component_bucket_size_bytes: 1024 * 1024, // 1 MiB
+                    // Garbage collection of the datastore is currently driven by the `MsgId`
+                    // component column, as a workaround for the `MsgId` mismatch issue.
+                    //
+                    // Since this component is only a few bytes large, trying to trigger a GC
+                    // based on bucket size is a lost cause, so make sure to have a small enough
+                    // row limit.
+                    //
+                    // TODO(cmc): Reasses once the whole `MsgId` mismatch issue is resolved
+                    // (probably once batching is implemented).
+                    component_bucket_nb_rows: 128,
+                    component_bucket_size_bytes: 10 * 1024 * 1024, // 10 MiB
                     // We do not garbage collect index buckets at the moment, and so the size of
                     // individual index buckets is irrelevant, only their total number of rows
                     // matter.
-                    // See <pr-link> for details.
+                    // See https://github.com/rerun-io/rerun/pull/1558 for details.
                     //
                     // TODO(cmc): Bring back index GC once the whole `MsgId` mismatch issue is
                     // resolved (probably once batching is implemented).