Clickhouse has special options "do_not_merge_across_partitions_select_final" for ReplaceMergeTree Engine, which allows make fast select on the "optimized" partitions. Unfortunate you have to run manually (crontab)  "OPTIMIZE TABLE ... PARTITION ... FINAL" . 

It will be great to have some options which will tell Clickhouse to compact older partitions on some conditions:

i.e.
```
CREATE TABLE select_final (t DateTime, x Int32, string String) ENGINE = ReplacingMergeTree() PARTITION BY toYYYYMMDD(t) ORDER BY (x, t)  SETTINGS optimize_partition_after = 3600
```
Clickhouse will check if a partition is older than 3600 seconds and has multiple parts and in such condition will do automatically optimization (compaction) 

P.S. we just discussed with @alexey-milovidov about this options :-) 




FutureMergedMutatedPartPtr future_part,
    const AllowedMergingPredicate & can_merge,
    const String & partition_id,
    bool final,
    const StorageMetadataPtr & metadata_snapshot,
    const MergeTreeTransactionPtr & txn,
    String * out_disable_reason,
    bool optimize_skip_merged_partitions)
{
    MergeTreeData::DataPartsVector parts = selectAllPartsFromPartition(partition_id);
    if (parts.empty())
    {