Class TableOptimizer

class TableOptimizer

Driver for running cleanup processes on a table. TableOptimizer provides functions for various cleanup processes that improve performance on a table. Only tables that have been modified using updates or deletes are candidates for cleanup. If the table descriptor corresponds to a sharded table, table optimizer processes each physical shard.

Public Functions

TableOptimizer(const TableDescriptor *td, Executor *executor, const Catalog_Namespace::Catalog &cat)

void recomputeMetadata() const

Recomputes per-chunk metadata for each fragment in the table. Updates and deletes can cause chunk metadata to become wider than the values in the chunk. Recomputing the metadata narrows the range to fit the chunk, as well as setting or unsetting the nulls flag as appropriate.

void recomputeMetadataUnlocked(const TableUpdateMetadata &table_update_metadata) const

Recomputes column chunk metadata for the given set of fragments. The caller of this method is expected to have already acquired the executor lock.

void vacuumDeletedRows() const

Compacts fragments to remove deleted rows. When a row is deleted, a boolean deleted system column is set to true. Vacuuming removes all deleted rows from a fragment. Note that vacuuming is a checkpointing operation, so data on disk will increase even though the number of rows for the current epoch has decreased.

void vacuumFragmentsAboveMinSelectivity(const TableUpdateMetadata &table_update_metadata) const

Vacuums fragments with a deleted rows percentage that exceeds the configured minimum vacuum selectivity threshold.

Private Functions

DeletedColumnStats recomputeDeletedColumnMetadata(const TableDescriptor *td, const std::set<size_t> &fragment_indexes = {}) const

void recomputeColumnMetadata(const TableDescriptor *td, const ColumnDescriptor *cd, const std::unordered_map<int, size_t> &tuple_count_map, std::optional<Data_Namespace::MemoryLevel> memory_level, const std::set<size_t> &fragment_indexes) const

std::set<size_t> getFragmentIndexes(const TableDescriptor *td, const std::set<int> &fragment_ids) const

void vacuumFragments(const TableDescriptor *td, const std::set<int> &fragment_ids = {}) const

DeletedColumnStats getDeletedColumnStats(const TableDescriptor *td, const std::set<size_t> &fragment_indexes) const

Private Members

const TableDescriptor *td_

Executor *executor_

const Catalog_Namespace::Catalog &cat_

Private Static Attributes

constexpr size_t ROW_SET_SIZE = {1000000000}