Eric Wolf

NAME

 Data::RecordStore - Simple store for text and byte data

SYNPOSIS

 use Data::RecordStore;

 $store = Data::RecordStore->open_store( $directory );
 $data = "TEXT OR BYTES";

 # the first record id is 1
 my $id = $store->stow( $data );

 my $new_or_recycled_id = $store->next_id;
 $store->stow( $new_data, $new_or_recycled_id );

 my $val = $store->fetch( $some_id );

 my $count = $store->entry_count;

 # delete the old record, make its id available for future
 # records
 $store->recycle_id( $id_to_recycle );

 $store->delete_record( $id_to_remove ); #deletes the old record

 my $has_id = $store->has_id( $someother_id );

 $store->empty; # clears out store completely

DESCRIPTION

Data::RecordStore is a simple way to store serialized text or byte data. It is written entirely in perl with no non-core dependencies. It is designed to be both easy to set up and easy to use. Space is automatically reclaimed when records are reycled or deleted.

Transactions (see below) can be created that stow and recycle records. They come with the standard commit and rollback methods. If a process dies in the middle of a commit or rollback, the operation can be reattempted. Incomplete transactions are obtained by the store's 'list_transactions' method.

Data::RecordStore operates directly and instantly on the file system. It is not a daemon or server and is not thread safe. It can be used in a thread safe manner if the controlling program uses locking mechanisms.

METHODS

open( directory )

Deprecated alias to open_store

open_store( directory )

Takes a directory, and constructs the data store in it. The directory must be writeable or creatible. If a RecordStore already exists there, it opens it, otherwise it creates a new one.

create_transaction()

Deprecated alias to start_transaction

start_transaction()

Creates and returns a transaction object

use_transaction()

Returns the current transaction. If there is no current transaction, it creates one and returns it.

commit_transaction()

Commits the current transaction, if any.

rollback_transaction()

Rolls back the current transaction, if any.

list_transactions

Returns a list of currently existing transaction objects not marked TRA_DONE.

stow( data, optionalID )

This saves the text or byte data to the record store. If an id is passed in, this saves the data to the record for that id, overwriting what was there. If an id is not passed in, it creates a new record store.

Returns the id of the record written to.

fetch( id )

Returns the record associated with the ID. If the ID has no record associated with it, undef is returned.

active_entry_count

Scans the index and returns a count of how many records are marked as having active data

record_count

Scans the silos and returns a count of how many records are contained in them.

entry_count

How many entries there are for records. This is equal to the highest ID that has been assigned minus the number of pending recycles. It is different from the record count, as entries may be marked deleted.

record_count

Return how many records there actually are

delete( id )

Deprecated alias to delete_record

delete_record( id )

Removes the entry with the given id from the store, freeing up its space. It does not reuse the id.

has_id( id )

  Returns true if an record with this id exists in the record store.

next_id

This sets up a new empty record and returns the id for it.

empty()

This empties out the entire record store completely. Use only if you mean it.

empty_recycler()

  Clears out all data from the recycler.

recycle( id, keep_data_flag )

  Ads the id to the recycler, so it will be returned when next_id is called.
  This removes the data occupied by the id, freeing up space unles
  keep_data_flag is set to true.

LIMITATIONS

Data::RecordStore is not thread safe. Thread coordination and locking can be done on a level above Data::RecordStore.

HELPER PACKAGE

Data::RecordStore::Transaction

HELPER DESCRIPTION

A transaction that can collect actions on the record store and then writes them as a block.

HELPER SYNOPSIS

my $transaction = $store->create_transaction;

print join(",", $transaction->get_update_time, $transaction->get_process_id, $transaction->get_state, $transaction->get_id );

my $new_id = $transaction->stow( $data );

my $new_or_recycled_id = $store->next_id;

$transaction->stow( "MORE DATA", $new_or_recycled_id );

$transaction->delete_record( $someid ); $transaction->recycle_id( $dead_id );

if( $is_good ) { $transaction->commit; } else { $transaction->rollback; }

# # Get a list of transactions that are old and probably stale. # for my $trans ($store->list_transactions) {

  next if $trans->get_udpate_time > $too_old;

  my $state = $trans->get_state;
  if( $state == Data::RecordStore::Transaction::TRA_IN_COMMIT
    || $state == Data::RecordStore::Transaction::TRA_CLEANUP_COMMIT )
  {
     $trans->commit;
  }
  elsif( $state == Data::RecordStore::Transaction::TRA_IN_ROLLBACK
    || $state == Data::RecordStore::Transaction::TRA_CLEANUP_ROLLBACK )
  {
     $trans->rollback;
  }
  elsif( $state == Data::RecordStore::Transaction::TRA_ACTIVE )
  {
     # commit or rollback, depending on preference
  }
}

METHODS

get_update_time

Returns the epoch time when the last time this was updated.

get_process_id

Returns the process id that last wrote to this transaction.

get_state

Returns the state of this process. Values are TRA_ACTIVE TRA_IN_COMMIT TRA_IN_ROLLBACK TRA_COMMIT_CLEANUP TRA_ROLLBACK_CLEANUP TRA_DONE

get_id

Returns the ID for this transaction, which is the same as its position in the transaction index plus one.

stow( $data, $optional_id )

Stores the data given. Returns the id that the data was stowed under. If the id is not given, this generates one from the record store. The data stored this way is really stored in the record store, but the index is not updated until a commit happens. That means it is not reachable from the store until the commit.

delete_record( $id )

Marks that the record associated with the id is to be deleted when the transaction commits.

recycle_id( $id )

Marks that the record associated with the id is to be deleted and its id recycled when the transaction commits.

commit()

Commit applies

Removes the file for this record store entirely from the file system.

AUTHOR Eric Wolf coyocanid@gmail.com

COPYRIGHT AND LICENSE

       Copyright (c) 2015-2018 Eric Wolf. All rights reserved.
       This program is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.

VERSION Version 4.06 (November, 2018))