Common subexpression elimination in columnar agg - #9534
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1) Use interning to find the identical expression subtrees and replace them with a canonical pointer. 1) Count how many times each expression is present in the hierarchy. 1) For expression that are present many times, compute them only once per batch.
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@antekresic, @dbeck: please review this pull request.
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1) Use interning to find the identical expression subtrees and replace them with a canonical pointer. 1) Count how many times each expression is present in the hierarchy. 1) For expression that are present many times, compute them only once per batch.
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## 2.29.0 (2026-07-28) This release contains performance improvements and bug fixes since the 2.28.3 release. We recommend that you upgrade at the next available opportunity. **Release Highlights** * **Chunk exclusion for DML operations** drastically improves the performance of `UPDATE` and `DELETE` statements on hypertables. By acquiring exclusive locks only on the specific chunks being modified rather than the entire hypertable, this enhancement eliminates massive lock contention and keeps high-concurrency workloads running smoothly without unnecessary slowdowns. * Intelligent **row-by-row decompression** enables the query planner to decompress data row-by-row rather than in large batches when an operation prioritizes a fast initial response (such as queries with `LIMIT` clauses). This dramatically reduces memory overhead and query latency, ensuring lightning-fast performance when you only need to retrieve a small subset of records from your compressed hypertables. **Important: PostgreSQL 15 Support Removed** TimescaleDB 2.29.0 removes support for PostgreSQL 15. This release supports PostgreSQL 16, 17, and 18. If you are still running PostgreSQL 15, upgrade PostgreSQL before upgrading to TimescaleDB 2.29.0. **Backward-Incompatible Changes** * [#10041](#10041) Remove support for PostgreSQL 15 **Features** * [#9315](#9315) Speed up `DML` operations on hypertables by using the optimized TimescaleDB hypertable expansion code instead of the generic PostgreSQL inheritance hierarchy expansion * [#9534](#9534) Speed up expression evaluation in the columnar pipeline by caching common subexpressions * [#9684](#9684) Add `_timescaledb_functions.decompress_batch()` SQL function * [#9732](#9732) Speed up some queries with small `LIMIT` by switching to row-by-row query execution pipeline * [#9917](#9917) Decompress less data in `DML` on compressed hypertables by accounting for prepared statement parameters * [#9957](#9957) Add `compact_chunk()` function * [#10048](#10048) Support concurrent refresh policies on hierarchical continuous aggregates * [#10081](#10081) Add `samplerate` argument to `_timescaledb_functions.estimate_uncompressed_size()` * [#10100](#10100) Skip classifying compressed relations to speed up planning * [#10118](#10118) Don't track compressed relations as separate chunk * [#10119](#10119) Reduce memory usage of `INSERT` queries using direct compress and spanning multiple chunks * [#10163](#10163) Add a compaction policy for unordered chunks * [#10204](#10204) Don't create separate hypertable catalog entry for hypertables with compression * [#10217](#10217) Initial placeholder version of granular refresh API * [#10225](#10225) Add `config_merge` parameter to `alter_job()` for merging `jsonb` into the existing job configuration * [#10226](#10226) Add `recompress_unordered` columnstore policy option * [#10231](#10231) Use `regclass` for storing relation reference in chunk table * [#10237](#10237) Add helper functions for decoding hypertable status * [#10240](#10240) Add the `tsdb.direct_compress` storage parameter that allows enabling direct compress for a given hypertable independent of global settings * [#10266](#10266) Add `max_batches` to `compact_chunk()` * [#10299](#10299) Add `continuous_aggs_tenant_tracking` and `hypertable_cagg_settings` catalogs **Bugfixes** * [#10013](#10013) Make ownership error messages on continuous aggregates consistent * [#10052](#10052) Result of `MIN` / `MAX` aggregate functions in columnar aggregation pipeline possibly inconsistent with plain PostgreSQL result * [#10071](#10071) Prune the real-time branch of hierarchical continuous aggregates at any nesting depth * [#10143](#10143) Fix division by zero when planning `time_bucket` with zero width * [#10199](#10199) Fix `initial_start` handling in `build_job_info` * [#10213](#10213) Cache sort pathkeys per hypertable * [#10221](#10221) Fix incremental refresh skipping the last bucket * [#10278](#10278) Drop `job_errors` view in `bgw_job_stat_history` migration * [#10280](#10280) `RETURNING` clause returned no rows for `INSERT` using direct compress * [#10281](#10281) Disable direct compress when the destination table has an exclusion constraint so the constraint is still enforced * [#10282](#10282) Only count directly compressed rows toward the command tag when the `INSERT` sets it * [#10286](#10286) Propagate `VACUUM` on a chunk to the compressed relation when running on the chunk directly * [#10302](#10302) Fix useless-join removal and self-join elimination for hypertables * [#10313](#10313) Allow running `ALTER EXTENSION timescaledb UPDATE` inside a transaction block * [#10315](#10315) Fix overlap detection with running max * [#10324](#10324) Fix stale index entries after `rebuild_sparse_index()` on compressed chunks **GUCs** * `timescaledb.enable_hypertable_expansion_for_dml`: allow using the optimized TimescaleDB hypertable expansion code for `UPDATE` and `DELETE` instead of the generic PostgreSQL inheritance hierarchy expansion. On by default. **Thanks** * @FrancescEthon and @ManuelEthon for reporting the issue * @h0rn3t for reporting a problem with `VACUUM` not propagating to the compressed relation * @MaximeEthon for reporting an issue with prepared statement parameters in DML decompression * @proddata for reporting a problem when upgrading from 2.15.3 to 2.28.2 * @tureba for reporting and fixing stale sparse-index entries after rebuild * @viniciusrsouza for reporting an issue with hierarchical continuous aggregates
svenklemm
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Jul 28, 2026
This release contains performance improvements and bug fixes since the 2.28.3 release. We recommend that you upgrade at the next available opportunity. **Release Highlights** * **Chunk exclusion for DML operations** drastically improves the performance of `UPDATE` and `DELETE` statements on hypertables. By acquiring exclusive locks only on the specific chunks being modified rather than the entire hypertable, this enhancement eliminates massive lock contention and keeps high-concurrency workloads running smoothly without unnecessary slowdowns. * Intelligent **row-by-row decompression** enables the query planner to decompress data row-by-row rather than in large batches when an operation prioritizes a fast initial response (such as queries with `LIMIT` clauses). This dramatically reduces memory overhead and query latency, ensuring lightning-fast performance when you only need to retrieve a small subset of records from your compressed hypertables. **Important: PostgreSQL 15 Support Removed** TimescaleDB 2.29.0 removes support for PostgreSQL 15. This release supports PostgreSQL 16, 17, and 18. If you are still running PostgreSQL 15, upgrade PostgreSQL before upgrading to TimescaleDB 2.29.0. **Backward-Incompatible Changes** * [#10041](#10041) Remove support for PostgreSQL 15 **Features** * [#9315](#9315) Speed up `DML` operations on hypertables by using the optimized TimescaleDB hypertable expansion code instead of the generic PostgreSQL inheritance hierarchy expansion * [#9534](#9534) Speed up expression evaluation in the columnar pipeline by caching common subexpressions * [#9684](#9684) Add `_timescaledb_functions.decompress_batch()` SQL function * [#9732](#9732) Speed up some queries with small `LIMIT` by switching to row-by-row query execution pipeline * [#9917](#9917) Decompress less data in `DML` on compressed hypertables by accounting for prepared statement parameters * [#9957](#9957) Add `compact_chunk()` function * [#10048](#10048) Support concurrent refresh policies on hierarchical continuous aggregates * [#10081](#10081) Add `samplerate` argument to `_timescaledb_functions.estimate_uncompressed_size()` * [#10100](#10100) Skip classifying compressed relations to speed up planning * [#10118](#10118) Don't track compressed relations as separate chunk * [#10119](#10119) Reduce memory usage of `INSERT` queries using direct compress and spanning multiple chunks * [#10163](#10163) Add a compaction policy for unordered chunks * [#10204](#10204) Don't create separate hypertable catalog entry for hypertables with compression * [#10217](#10217) Initial placeholder version of granular refresh API * [#10225](#10225) Add `config_merge` parameter to `alter_job()` for merging `jsonb` into the existing job configuration * [#10226](#10226) Add `recompress_unordered` columnstore policy option * [#10231](#10231) Use `regclass` for storing relation reference in chunk table * [#10237](#10237) Add helper functions for decoding hypertable status * [#10240](#10240) Add the `tsdb.direct_compress` storage parameter that allows enabling direct compress for a given hypertable independent of global settings * [#10266](#10266) Add `max_batches` to `compact_chunk()` * [#10299](#10299) Add `continuous_aggs_tenant_tracking` and `hypertable_cagg_settings` catalogs **Bugfixes** * [#10013](#10013) Make ownership error messages on continuous aggregates consistent * [#10052](#10052) Result of `MIN` / `MAX` aggregate functions in columnar aggregation pipeline possibly inconsistent with plain PostgreSQL result * [#10071](#10071) Prune the real-time branch of hierarchical continuous aggregates at any nesting depth * [#10143](#10143) Fix division by zero when planning `time_bucket` with zero width * [#10199](#10199) Fix `initial_start` handling in `build_job_info` * [#10213](#10213) Cache sort pathkeys per hypertable * [#10221](#10221) Fix incremental refresh skipping the last bucket * [#10278](#10278) Drop `job_errors` view in `bgw_job_stat_history` migration * [#10280](#10280) `RETURNING` clause returned no rows for `INSERT` using direct compress * [#10281](#10281) Disable direct compress when the destination table has an exclusion constraint so the constraint is still enforced * [#10282](#10282) Only count directly compressed rows toward the command tag when the `INSERT` sets it * [#10286](#10286) Propagate `VACUUM` on a chunk to the compressed relation when running on the chunk directly * [#10302](#10302) Fix useless-join removal and self-join elimination for hypertables * [#10313](#10313) Allow running `ALTER EXTENSION timescaledb UPDATE` inside a transaction block * [#10315](#10315) Fix overlap detection with running max * [#10324](#10324) Fix stale index entries after `rebuild_sparse_index()` on compressed chunks **GUCs** * `timescaledb.enable_hypertable_expansion_for_dml`: allow using the optimized TimescaleDB hypertable expansion code for `UPDATE` and `DELETE` instead of the generic PostgreSQL inheritance hierarchy expansion. On by default. **Thanks** * @FrancescEthon and @ManuelEthon for reporting an issue with incremental refresh skipping the last bucket * @h0rn3t for reporting a problem with `VACUUM` not propagating to the * @igor2x for reporting an issue with locking during DML statements on hypertables compressed relation * @MaximeEthon for reporting an issue with prepared statement parameters in DML decompression * @proddata for reporting a problem when upgrading from 2.15.3 to 2.28.2 * @tureba for reporting and fixing stale sparse-index entries after rebuild * @viniciusrsouza for reporting an issue with hierarchical continuous aggregates
surister
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Jul 28, 2026
This release contains performance improvements and bug fixes since the 2.28.3 release. We recommend that you upgrade at the next available opportunity. **Release Highlights** * **Chunk exclusion for DML operations** drastically improves the performance of `UPDATE` and `DELETE` statements on hypertables. By acquiring exclusive locks only on the specific chunks being modified rather than the entire hypertable, this enhancement eliminates massive lock contention and keeps high-concurrency workloads running smoothly without unnecessary slowdowns. * Intelligent **row-by-row decompression** enables the query planner to decompress data row-by-row rather than in large batches when an operation prioritizes a fast initial response (such as queries with `LIMIT` clauses). This dramatically reduces memory overhead and query latency, ensuring lightning-fast performance when you only need to retrieve a small subset of records from your compressed hypertables. **Important: PostgreSQL 15 Support Removed** TimescaleDB 2.29.0 removes support for PostgreSQL 15. This release supports PostgreSQL 16, 17, and 18. If you are still running PostgreSQL 15, upgrade PostgreSQL before upgrading to TimescaleDB 2.29.0. **Backward-Incompatible Changes** * [timescale#10041](timescale#10041) Remove support for PostgreSQL 15 **Features** * [timescale#9315](timescale#9315) Speed up `DML` operations on hypertables by using the optimized TimescaleDB hypertable expansion code instead of the generic PostgreSQL inheritance hierarchy expansion * [timescale#9534](timescale#9534) Speed up expression evaluation in the columnar pipeline by caching common subexpressions * [timescale#9684](timescale#9684) Add `_timescaledb_functions.decompress_batch()` SQL function * [timescale#9732](timescale#9732) Speed up some queries with small `LIMIT` by switching to row-by-row query execution pipeline * [timescale#9917](timescale#9917) Decompress less data in `DML` on compressed hypertables by accounting for prepared statement parameters * [timescale#9957](timescale#9957) Add `compact_chunk()` function * [timescale#10048](timescale#10048) Support concurrent refresh policies on hierarchical continuous aggregates * [timescale#10081](timescale#10081) Add `samplerate` argument to `_timescaledb_functions.estimate_uncompressed_size()` * [timescale#10100](timescale#10100) Skip classifying compressed relations to speed up planning * [timescale#10118](timescale#10118) Don't track compressed relations as separate chunk * [timescale#10119](timescale#10119) Reduce memory usage of `INSERT` queries using direct compress and spanning multiple chunks * [timescale#10163](timescale#10163) Add a compaction policy for unordered chunks * [timescale#10204](timescale#10204) Don't create separate hypertable catalog entry for hypertables with compression * [timescale#10217](timescale#10217) Initial placeholder version of granular refresh API * [timescale#10225](timescale#10225) Add `config_merge` parameter to `alter_job()` for merging `jsonb` into the existing job configuration * [timescale#10226](timescale#10226) Add `recompress_unordered` columnstore policy option * [timescale#10231](timescale#10231) Use `regclass` for storing relation reference in chunk table * [timescale#10237](timescale#10237) Add helper functions for decoding hypertable status * [timescale#10240](timescale#10240) Add the `tsdb.direct_compress` storage parameter that allows enabling direct compress for a given hypertable independent of global settings * [timescale#10266](timescale#10266) Add `max_batches` to `compact_chunk()` * [timescale#10299](timescale#10299) Add `continuous_aggs_tenant_tracking` and `hypertable_cagg_settings` catalogs **Bugfixes** * [timescale#10013](timescale#10013) Make ownership error messages on continuous aggregates consistent * [timescale#10052](timescale#10052) Result of `MIN` / `MAX` aggregate functions in columnar aggregation pipeline possibly inconsistent with plain PostgreSQL result * [timescale#10071](timescale#10071) Prune the real-time branch of hierarchical continuous aggregates at any nesting depth * [timescale#10143](timescale#10143) Fix division by zero when planning `time_bucket` with zero width * [timescale#10199](timescale#10199) Fix `initial_start` handling in `build_job_info` * [timescale#10213](timescale#10213) Cache sort pathkeys per hypertable * [timescale#10221](timescale#10221) Fix incremental refresh skipping the last bucket * [timescale#10278](timescale#10278) Drop `job_errors` view in `bgw_job_stat_history` migration * [timescale#10280](timescale#10280) `RETURNING` clause returned no rows for `INSERT` using direct compress * [timescale#10281](timescale#10281) Disable direct compress when the destination table has an exclusion constraint so the constraint is still enforced * [timescale#10282](timescale#10282) Only count directly compressed rows toward the command tag when the `INSERT` sets it * [timescale#10286](timescale#10286) Propagate `VACUUM` on a chunk to the compressed relation when running on the chunk directly * [timescale#10302](timescale#10302) Fix useless-join removal and self-join elimination for hypertables * [timescale#10313](timescale#10313) Allow running `ALTER EXTENSION timescaledb UPDATE` inside a transaction block * [timescale#10315](timescale#10315) Fix overlap detection with running max * [timescale#10324](timescale#10324) Fix stale index entries after `rebuild_sparse_index()` on compressed chunks **GUCs** * `timescaledb.enable_hypertable_expansion_for_dml`: allow using the optimized TimescaleDB hypertable expansion code for `UPDATE` and `DELETE` instead of the generic PostgreSQL inheritance hierarchy expansion. On by default. **Thanks** * @FrancescEthon and @ManuelEthon for reporting an issue with incremental refresh skipping the last bucket * @h0rn3t for reporting a problem with `VACUUM` not propagating to the * @igor2x for reporting an issue with locking during DML statements on hypertables compressed relation * @MaximeEthon for reporting an issue with prepared statement parameters in DML decompression * @proddata for reporting a problem when upgrading from 2.15.3 to 2.28.2 * @tureba for reporting and fixing stale sparse-index entries after rebuild * @viniciusrsouza for reporting an issue with hierarchical continuous aggregates
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them with a canonical pointer.
per batch.