feat: utxo set cache

[fpelliccioni]

No description provided.

[Copilot]

Pull Request Overview

This PR introduces a UTXO set cache along with changes to database and block caching settings. The key changes are:

• Increasing default database size constants for mainnet.
• Adding a new block_cache_capacity setting and integrating a block cache in the database.
• Updating UTXO-related functions and refactoring internal database operations.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/settings.cpp	Updated database size constants and added block_cache_capacity.
src/data_base.cpp	Introduced block cache initialization and duplicate cache flush calls in close().
include/kth/database/databases/utxo_database.ipp	Renamed insert_utxo to insert_utxo_with_fixed_data for clarity.
include/kth/database/databases/internal_database.*	Switched from std::unordered_map/set to boost::unordered_flat_map/set for UTXO handling.
include/kth/database/data_base.hpp	Added block_cache_t implementation to support the new UTXO cache.

Comments suppressed due to low confidence (1)

include/kth/database/databases/utxo_database.ipp:37

• Ensure that the new function name insert_utxo_with_fixed_data is used consistently throughout the project and update references accordingly.

result_code internal_database_basis<Clock>::insert_utxo_with_fixed_data(domain::chain::output_point const& point, domain::chain::output const& output, data_chunk const& fixed_data, KTH_DB_txn* db_txn) {

[Copilot]

[nitpick] Consider adding a comment to explain the role of block_cache_capacity and the rationale behind its default value.

Suggested change

	, cache_capacity(0)
	, cache_capacity(0)
	// Specifies the maximum number of blocks that can be cached in memory.
	// The default value of 100 is chosen as a balance between memory usage and performance.

[Copilot]

Duplicate call to flush_to_db() in the close() method may result in unnecessary double flushing. Confirm if this is intended or remove the redundant call.

Suggested change

	LOG_INFO(LOG_DATABASE, "Flushing the block cache to DB (again)...");
	block_cache_->flush_to_db();
	LOG_INFO(LOG_DATABASE, "Block cache flushed to DB.");

[Copilot]

[nitpick] Consider capturing and handling the return result of push_blocks_and_utxos to log potential issues and ensure robust error handling during block cache flush operations.

Suggested change

	db_->push_blocks_and_utxos(blocks_, start_height_, utxo_map_, utxo_to_remove_, is_stale());
	auto result = db_->push_blocks_and_utxos(blocks_, start_height_, utxo_map_, utxo_to_remove_, is_stale());
	if (result != result_code::success) {
	LOG_ERROR(LOG_DATABASE, "Failed to flush block cache to database. Error code: ", result);
	}