ydb filer store

[kmlebedev]

#2942

[kmlebedev]

@chrislusf Checked filer starts here

[kmlebedev]

@chrislusf I'm done, all tests passed except #3011

[chrislusf]

you may need to add one empty file to the ydb folder, to ensure compilation when "ydb" tag is not defined.

[kmlebedev]

you may need to add one empty file to the ydb folder, to ensure compilation when "ydb" tag is not defined.

done

[rekby]

YDB has limit for return rows (default - 1000).
The client code must check Truncated() flag to detect if response truncated (and select next page/return error).

res.CurrentResultSet().Truncated()

[kmlebedev]

@rekby How to get this page if the request already has a limit and a start name ?
Perhaps there are regular means without changing the select query ?

		SELECT name, meta
		FROM filemeta
		WHERE dir_hash = $dir_hash AND directory = $directory and name >= $start_name and name LIKE $prefix
		ORDER BY name ASC LIMIT $limit;`

[chrislusf]

Please add some tests similar to weed/filer/etcd/etcd_store_test.go in d5fe5d1

[kmlebedev]

add some tests

done #3043