fdb overlay

Make the contents of one FDB database available as though they were archived using different keys (class or expver).

The new database behaves as though it has a symlink to the old, and any data retrieved will have the relevant keys updated on retrieval (on the fly).

Because data is rewritten on the fly, there may be a significant performance penalty when reading data from an overlaid FDB.

Usage

fdb overlay [options] [source DB request] [target DB request]

Options

At least one of class or expver is required is required

--force

Apply overlay even if the target database already exists

--remove

Remove a previously applied FDB overlay. Once an overlay has been removed, it cannot be reapplied.

--variable-keys=string,string
Specify the keys that may vary between mounted DBs.
Defaults: class,expver
Currently the code that sets values on the GRIB messages only supports string values. If the set of
keys is extended, the user must ensure that only string type keys are used.

--config=string

FDB configuration filename

Example

Add overlay

% fdb overlay class=rd,expver=xxxx,stream=oper,date=20160907,time=0000 class=rd,expver=xxxz,stream=oper,date=20160907,time=0000
Applying {class=rd,expver=xxxx,stream=oper,date=20160907,time=0000,domain=g} (Rule[line=127]) onto {class=rd,expver=xxxz,stream=oper,date=20160907,time=0000,domain=g} (Rule[line=127])

This overlay can be removed

% fdb overlay --remove class=rd,expver=xxxx,stream=oper,date=20160907,time=0000 class=rd,expver=xxxz,stream=oper,date=20160907,time=0000
Removing {class=rd,expver=xxxx,stream=oper,date=20160907,time=0000,domain=g} (Rule[line=127]) from {class=rd,expver=xxxz,stream=oper,date=20160907,time=0000,domain=g} (Rule[line=127])