* libs/db: conditional compilation
For cleveldb: go build -tags cleveldb
For boltdb: go build -tags boltdb
Fixes#3611
* document db_backend param better
* remove deprecated LevelDBBackend
* update changelog
* add missing lines
* add new line
* fix TestRemoteDB
* add a line about boltdb tag
* Revert "remove deprecated LevelDBBackend"
This reverts commit 1aa85453f76605e0c4d967601bbe26240e668d51.
* make PR non breaking
* change DEPRECATED label format
https://stackoverflow.com/a/36360323/820520
Description:
add boltdb implement for db interface.
The boltdb is safe and high performence embedded KV database. It is based on B+tree and Mmap.
Now it is maintained by etcd-io org. https://github.com/etcd-io/bbolt
It is much better than LSM tree (levelDB) when RANDOM and SCAN read.
Replaced #3604
Refs #1835
Commits:
* add boltdb for storage
* update boltdb in gopkg.toml
* update bbolt in Gopkg.lock
* dep update Gopkg.lock
* add boltdb'bucket when create Boltdb
* some modifies
* address my own comments
* fix most of the Iterator tests for boltdb
* bolt does not support concurrent writes while iterating
* add WARNING word
* note that ReadOnly option is not supported
* fixes after Ismail's review
Co-Authored-By: melekes <anton.kalyaev@gmail.com>
* panic if View returns error
plus specify bucket in the top comment
