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8.1 Compression

Compressing the index reduces disk space consumption and speeds up the indexing by reducing I/O.

Compressing at the mifluz level would imply choosing complicated key structures, slowing down and complexifying insert and delete operations. We have chosen to do the compression within Berkeley DB in the memory pool subsystem. Berkeley DB keeps fixed size pages in a memory cache, when it is full it writes the least recently used pages to disk. When a page is needed Berkeley DB looks for it in memory and retrieves it from disk if its not in memory. The compression/uncompression occurs when a page moves between the memory pool and the disk.

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