Check and resize if needed at batch transaction start

This currently only affects blockchain_import and blockchain_converter.

When the number of blocks expected for the batch transaction is
provided, make an estimate of the DB space needed. If not enough free
space remains, resize the DB.

The estimate is made based on:
- the average size of the last 500 blocks, or if larger, a min. block
  size of 4k
- a factor for the expanded size a block occupies in the DB across the
  sub-dbs/tables
- a safety factor (1.7) to allow for a "reasonable" average block size
  increase over the batch

Increase the DB size by whichever is greater: the estimated size needed
or a minimum increase size, currently 128 MB.

The conservative factors in the estimate help in testing that the resize
occurs when needed, and without gratuitous size increases. For common
use, the safety factor and minimum increase size could reasonably be
increased.

For testing, setting DEFAULT_MAPSIZE (blockchain_db/lmdb/db_lmdb.h) to 1
<< 27 (128 MB) and recompiling will ensure DB resizes take place sooner
and more frequently.

0 files changed, 0 insertions, 0 deletions