Release 2.22.0 (#8536)

## 2.22.0 (2025-09-02)

This release contains performance improvements and bug fixes since the 2.21.3 release. We recommend that you upgrade at the next available opportunity.

**Highlighted features in TimescaleDB v2.22.0**
* Sparse indexes on compressed hypertables can now be explicitly configured via `ALTER TABLE` rather than relying only on internal heuristics. Users can define indexes on multiple columns to improve query performance for their specific workloads.
* [Tech Preview] Continuous aggregates now support the `timescaledb.invalidate_using` option, enabling invalidations to be collected either via triggers on the hypertable or directly from WAL using logical decoding. Aggregates inherit the hypertable’s method if none is specified.  
* UUIDv7 compression and vectorization are now supported. The compression algorithm leverages the timestamp portion for delta-delta compression while storing the random portion separately. The vectorized equality/inequality filters with bulk decompression deliver ~2× faster query performance. The feature is disabled by default (`timescaledb.enable_uuid_compression`) to simplify the downgrading experience, and will be enabled out of the box in the next minor release.
* Hypertables can now be partitioned by UUIDv7 columns, leveraging their embedded timestamps for time-based chunking. We’ve also added utility functions to simplify working with UUIDv7, such as generating values or extracting timestamps - e.g., `uuid_timestamp()` returns a PostgreSQL timestamp from a UUIDv7.
* SkipScan now supports multi-column indexes in not-null mode, improving performance for distinct and ordered queries across multiple keys.  

**Removal of the hypercore table access method**
We made the decision to deprecate the hypercore table access method (TAM) with the 2.21.0 release. Hypercore TAM was an experiment and it did not show the performance improvements we hoped for. It is removed with this release. Upgrades to 2.22.0 and higher are blocked if TAM is still in use. Since TAM’s inception in [2.18.0](https://github.com/timescale/timescaledb/releases/tag/2.18.0), we learned that btrees were not the right architecture. Recent advancements in the columnstore, such as more performant backfilling, SkipScan, adding check constraints, and faster point queries, put the [columnstore](https://www.timescale.com/blog/hypercore-a-hybrid-row-storage-engine-for-real-time-analytics) close to or on par with TAM without needing to store an additional index. We apologize for the inconvenience this action potentially causes and are here to assist you during the migration process.

Migration path

```
do $$
declare
   relid regclass;
begin
   for relid in
       select cl.oid from pg_class cl
       join pg_am am on (am.oid = cl.relam)
       where am.amname = 'hypercore'
   loop
       raise notice 'converting % to heap', relid::regclass;
       execute format('alter table %s set access method heap', relid);
   end loop;
end
$$;
```

**Features**
* [#8247](#8247) Add configurable alter settings for sparse indexes
* [#8306](#8306) Add option for invalidation collection using WAL for continuous aggregates
* [#8340](#8340) Improve selectivity estimates for sparse minmax indexes, so that an index scan on a table in the columnstore is chosen more often when it's beneficial.
* [#8360](#8360) Continuous aggregate multi-hypertable invalidation processing
* [#8364](#8364) Remove hypercore table access method
* [#8371](#8371) Show available timescaledb `ALTER` options when encountering unsupported options
* [#8376](#8376) Change `DecompressChunk` custom node name to `ColumnarScan`
* [#8385](#8385) UUID v7 functions for testing pre PG18
* [#8393](#8393) Add specialized compression for UUIDs. Best suited for UUID v7, but still works with other UUID versions. This is experimental at the moment and backward compatibility is not guaranteed.
* [#8398](#8398) Set default compression settings at compress time
* [#8401](#8401) Support `ALTER TABLE RESET` for compression settings
* [#8414](#8414) Vectorised filtering of UUID Eq and Ne filters, plus bulk decompression of UUIDs
* [#8424](#8424) Block downgrade when orderby setting is `NULL`
* [#8454](#8454) Remove internal unused index helper functions
* [#8494](#8494) Improve job stat history retention policy
* [#8496](#8496) Fix dropping chunks with foreign keys
* [#8505](#8505) Add support for partitioning on UUIDv7
* [#8513](#8513) Support multikey SkipScan when all keys are guaranteed to be non-null
* [#8514](#8514) Concurrent continuous aggregates improvements
* [#8528](#8528) Add the `_timescaledb_functions.chunk_status_text` helper function
* [#8529](#8529) Optimize direct compress status handling

**Bugfixes**
* [#8422](#8422) Don't require `columnstore=false` when using the TimescaleDB Apache 2 Edition
* [#8493](#8493) Change log level of `not null` constraint message
* [#8500](#8500) Fix uniqueness check with generated columns and hypercore
* [#8545](#8545) Fix error in LOCF/Interpolate with out-of-order and repeated columns
* [#8558](#8558) Error out on bad args when processing invalidation
* [#8559](#8559) Fix `timestamp out of range` using `end_offset=NULL` on CAgg refresh policy

**GUCs**
* `enable_multikey_skipscan`: Enable SkipScan for multiple distinct keys, default: on
* `enable_uuid_compression`: Enable UUID compression functionality, default: off
* `cagg_processing_wal_batch_size`: Batch size when processing WAL entries, default: 10000
* `cagg_processing_low_work_mem`: Low working memory limit for continuous aggregate invalidation processing, default: 38.4MB
* `cagg_processing_high_work_mem`: High working memory limit for continuous aggregate invalidation processing, default: 51.2MB

**Thanks**
* @CodeTherapist for reporting an issue where foreign key checks did not work after several insert statements
* @moodgorning for reporting a bug in queries with LOCF/Interpolate using out-of-order columns
* @nofalx for reporting an error when using `end_offset=NULL` on CAgg refresh policy
* @pierreforstmann for fixing a bug that happened when dropping chunks with foreign keys
* @Zaczero for reporting a bug with CREATE TABLE WITH when using the TimescaleDB Apache 2 Edition

Author: timescale-automation