Quote from: vector76 on August 14, 2011, 01:37:17 PM

Great work, I just have a question about the span. I don't understand how it works, because if you fork the block chain, won't all the existing span numbers have to be incremented?

I've been trying to implement a sqlite backend (so far just dump to sqlite which is mostly working), and it seems to be helpful to distinguish between dynamic data and data which is immutable such as the successor relationship between blocks, transaction containment within a block, etc.

Whether a block is in the best chain and whether a txout has been spent in the best chain is dynamic, so I have to implement queries that more or less correspond to ConnectBlock and DisconnectBlock. I would love to be able to eliminate it using your span mechanism or something similar but I'm not understanding how it works.

I'm still working on ProcessBlock (verifying the blocks) and everything below it (ConnectBlock/DisconnectBlock). You can see an example of how the span works in src/storage/postgresql_storage.cpp:reorganize_block_chain()... That function will be moved internally and within verify_block under include/bitcoin/verify.hpp

Indeed you're correct that all the spans of the parents would have to be incremented if you fork the block chain. This is OK since it can be done in a simple single UPDATE, inserting a new block is an infrequent operation (doesn't have to be as fast as SELECTs) and it's not a big deal if adding a new block isn't immediate.

Far more important is the select speed. If you run the poller and postgres benchmark:

Code:

$ ./bin/examples/poller dbname dbuser dbpass localhost:8333
... wait to download all the blocks
$ make psql
$ time ./bin/tests/psql
... run benchmark to fetch 100 blocks

With my current setup it takes 10 secs to fetch 100 blocks or 0.1 secs for 1 block. That means 4 hours to fetch the entire block-chain of 140k blocks. Using a rule of thumb that verifying the block-chain will be 10 times as slow, that might mean 40 hours to verify all 140k blocks. ATM I plan to just bundle the first 120k pre-verified blocks in the code, then later see about optimising this.

But I am running it over a VPS on rackspace, so that also could be a reason for the speed too.

It should be possible for you to easily modify the current storage engine I'm using to enable sqllite... The library supports multiple backends. See the constructor in src/storage/postgresql_storage.cpp:postgresql_storage() ... The sql_ object is being explicitly initialised with postgresql parameters. I don't mind making this a generic sql_storage backend if you're able to get it to work

The current way of joining the blocks using reorganize_block_chain() will be removed and done as part of the block-chain verification- that's the best way I see currently to do it... But I am doing more research of the current bitcoin sourcecode to make sure I understand everything fully. The current bitcoin is very inefficient/obtuse and there's a whole bunch of ways to do things quicker or nicer.