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From serkanmulayim@gmail.com <serkanmula...@gmail.com>
Subject Re: [lucy-user] C library - RAM index serialization/deserialization
Date Tue, 03 Apr 2018 20:22:20 GMT
I made a test by creating a new method, Folder_Consolidate2 which does NOT call CFWriter_Consolidate.
This one works. And it was only for testing purposes (I am not changing the source code).
Is there a way to get the ivars struct for folder somehow? This would make things much easier
for me.

If this is not feasible, extending the RAM_Folder to contain a new consolidate method which
does not call the CFWriter_Consolidate method might be an option. If I need to move this way,
what is the best way to have the new subclass which would not mess up the casting of the pointers.?

I am still open to other suggestions though.

Thanks,
Serkan


On 2018/04/03 17:26:57, serkanmulayim@gmail.com <serkanmulayim@gmail.com> wrote: 
> Hi Nick,
> 
> Thank you very much for your response. I was exactly stuck on what you mentioned. I need
to create an entry for the folder with the CFReader, but there is no internal functions supporting
that. Folder implementation fails since it does a check for the cfmeta.json.
> 
> Secondly it does not seem like I can link CFReader (Folder*) as an entry to the enclosing
folder since there is no function to link a folder inside a folder as far as I see. Can you
confirm?
> 
> If the above is not an option, I was thinking of subclassing RAMFolder. I do not think
I need to create a cfh file for that, but I will create my own Folder implementation with
a static header file. I think this is the right approach. (Unless there is a better approach
which does not require subclassing, e.g. by using inStreams)
> 
> Thanks again,
> Serkan
> 
> On 2018/04/03 13:26:43, Nick Wellnhofer <wellnhofer@aevum.de> wrote: 
> > On 02/04/2018 19:52, serkanmulayim@gmail.com wrote:
> > > I realized that it is not possible to serialize the RAM index directly to bytes.
This is why I made some tests to copy all files in the ram folder to FS folder by iterating
over the contents for the RAM folder.
> > 
> > Yes, you have to inspect the RAMFolder using the private API of Folder, 
> > FileHandle, InStream, etc. It's documented in the .cfh files in 
> > core/Lucy/Store but it seems that you already figured this out.
> > 
> >      https://git1-us-west.apache.org/repos/asf?p=lucy.git;a=tree;f=core/Lucy/Store
> > 
> > > Why are there these virtual files? (I suspect that for optimization purposes
(e.g. in order not to read the cfmeta.json file over again), virtual files hold the cfmeta.json
values). So my question is, is it possible to create the virtual files from cfmeta.json value
with an API call? Or do you have any other suggestions.
> > 
> > These are so-called "compound files" used to consolidate multiple files into a 
> > single one and reduce the number of open file handles. On the filesystem 
> > level, there are two files cfmeta.json and cf.dat but Lucy's Store API 
> > automatically returns information about the virtual files. If you want to 
> > treat compound files as regular files, you have to check the Folder objects 
> > returned by Folder_Find_Folder. If it's a Lucy::Store::CompoundFileReader, 
> > call CFReader_Get_Real_Folder to get the actual RAMFolder or FSFolder:
> > 
> >      if (Folder_is_a(subfolder, COMPOUNDFILEREADER)) {
> >          CompoundFileReader *cf_reader = (CompoundFileReader*)subfolder;
> >          subfolder = CFReader_Get_Real_Folder(cf_reader);
> >      }
> > 
> > After deserializing cfmeta.json and cf.dat into a RAMFolder, you'll have to 
> > recreate the CFReaders and replace the entry in the enclosing folder. Have a 
> > look at Folder_Consolidate to get the idea. But the `entries` hash isn't 
> > exposed, so you probably can't do that without changes to the Lucy source code.
> > 
> > As an alternative, you could try to change Lucy's behavior to not create 
> > compound files for RAMFolders at all. Subclassing RAMFolder and making 
> > Folder_Consolidate a no-op should work.
> > 
> > Nick
> > 
> 

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