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+.\" ========================================================================
+.\"
+.IX Title "Data::Stream::Bulk 3"
+.TH Data::Stream::Bulk 3 "2009-07-11" "perl v5.8.7" "User Contributed Perl Documentation"
+.\" For nroff, turn off justification. Always turn off hyphenation; it makes
+.\" way too many mistakes in technical documents.
+.if n .ad l
+.nh
+.SH "NAME"
+Data::Stream::Bulk \- N at a time iteration API
+.SH "SYNOPSIS"
+.IX Header "SYNOPSIS"
+.Vb 2
+\& # get a bulk stream from somewere
+\& my $s = Data::Stream::Bulk::Foo\->new( ... );
+\&
+\& # can be used like this:
+\& until ( $s\->is_done ) {
+\& foreach my $item ( $s\->items ) {
+\& process($item);
+\& }
+\& }
+\&
+\& # or like this:
+\& while( my $block = $s\->next ) {
+\& foreach my $item ( @$block ) {
+\& process($item);
+\& }
+\& }
+.Ve
+.SH "DESCRIPTION"
+.IX Header "DESCRIPTION"
+This module tries to find middle ground between one at a time and all at once
+processing of data sets.
+.PP
+The purpose of this module is to avoid the overhead of implementing an
+iterative api when this isn't necessary, without breaking forward
+compatibility in case that becomes necessary later on.
+.PP
+The \s-1API\s0 optimizes for when a data set typically fits in memory and is returned
+as an array, but the consumer cannot assume that the data set is bounded.
+.PP
+The \s-1API\s0 is destructive in order to minimize the chance that resultsets are
+leaked due to improper usage.
+.SH "API"
+.IX Header "API"
+.SS "Required Methods"
+.IX Subsection "Required Methods"
+The \s-1API\s0 requires two methods to be implemented:
+.IP "is_done" 4
+.IX Item "is_done"
+Should return true if the stream is exhausted.
+.Sp
+As long as this method returns a false value (not done) \f(CW\*(C`next\*(C'\fR could
+potentially return another block.
+.IP "next" 4
+.IX Item "next"
+Returns the next block.
+.Sp
+Note that \f(CW\*(C`next\*(C'\fR is not guaranteed to return an array reference, even if
+\&\f(CW\*(C`is_done\*(C'\fR returned false prior to calling it.
+.SS "Convenience Methods"
+.IX Subsection "Convenience Methods"
+.IP "items" 4
+.IX Item "items"
+This method calls \f(CW\*(C`next\*(C'\fR and dereferences the result if there are pending
+items.
+.IP "all" 4
+.IX Item "all"
+Force evaluation of the entire resultset.
+.Sp
+Note that for large data sets this might cause swap thrashing of various other
+undesired effects. Use with caution.
+.ie n .IP "cat @streams" 4
+.el .IP "cat \f(CW@streams\fR" 4
+.IX Item "cat @streams"
+Concatenates this stream with \f(CW@streams\fR, returning a single stream.
+.ie n .IP "list_cat @tail" 4
+.el .IP "list_cat \f(CW@tail\fR" 4
+.IX Item "list_cat @tail"
+Returns a possibly cleaned up list of streams.
+.Sp
+Used by \f(CW\*(C`cat\*(C'\fR.
+.Sp
+Overridden by Data::Stream::Bulk::Array, Data::Stream::Bulk::Cat and
+Data::Stream::Bulk::Nil to implement some simple short circuiting.
+.ie n .IP "filter $filter" 4
+.el .IP "filter \f(CW$filter\fR" 4
+.IX Item "filter $filter"
+Applies a per-block block filter to the stream.
+.Sp
+Returns a possibly new stream with the filtering layered.
+.Sp
+\&\f(CW$filter\fR is invoked once per block and should return an array reference to
+the filtered block.
+.IP "loaded" 4
+.IX Item "loaded"
+Should be overridden to return true if all the items are already realized (e.g.
+in the case of Data::Stream::Bulk::Array).
+.Sp
+Returns false by default.
+.Sp
+When true calling \f(CW\*(C`all\*(C'\fR is supposed to be safe (memory usage should be in the
+same order of magnitude as stream's own usage).
+.Sp
+This is typically useful when tranforming an array is easier than transorming a
+stream (e.g. optional duplicate filtering).
+.SH "CLASSES"
+.IX Header "CLASSES"
+.IP "Data::Stream::Bulk::Array" 4
+.IX Item "Data::Stream::Bulk::Array"
+This class is not a stream at all, but just one block. When the data set easily
+fits in memory this class can be used, while retaining forward compatibility
+with larger data sets.
+.IP "Data::Stream::Bulk::Callback" 4
+.IX Item "Data::Stream::Bulk::Callback"
+Callback driven iteration.
+.IP "Data::Stream::Bulk::DBI" 4
+.IX Item "Data::Stream::Bulk::DBI"
+Bulk fetching of data from \s-1DBI\s0 statement handles.
+.IP "Data::Stream::Bulk::DBIC" 4
+.IX Item "Data::Stream::Bulk::DBIC"
+DBIx::Class::ResultSet iteration.
+.IP "Data::Stream::Bulk::Nil" 4
+.IX Item "Data::Stream::Bulk::Nil"
+An empty result set.
+.IP "Data::Stream::Bulk::Cat" 4
+.IX Item "Data::Stream::Bulk::Cat"
+A concatenation of several streams.
+.IP "Data::Stream::Bulk::Filter" 4
+.IX Item "Data::Stream::Bulk::Filter"
+A filter wrapping a stream.
+.SH "SEE ALSO"
+.IX Header "SEE ALSO"
+HOP::Stream, Iterator, Class::Iterator etc for one by one iteration
+.PP
+\&\s-1DBI\s0, DBIx::Class::ResultSet
+.PP
+POE::Filter
+.PP
+Data::Page
+.PP
+Parallel::Iterator
+.PP
+<http://en.wikipedia.org/wiki/MapReduce>, \s-1LISP\s0, and all that other kool aid
+.SH "TODO"
+.IX Header "TODO"
+.IP "Sorted streams" 4
+.IX Item "Sorted streams"
+Add a hint for sorted streams (like \f(CW\*(C`loaded\*(C'\fR but as an attribute in the base
+role).
+.Sp
+Introduce a \f(CW\*(C`merge\*(C'\fR operation for merging of sorted streams.
+.Sp
+Optimize \f(CW\*(C`unique\*(C'\fR to make use of sorting hints for constant space uniquing.
+.IP "More utility functions" 4
+.IX Item "More utility functions"
+To assist in proccessing and creating streams.
+.IP "Coercion tables" 4
+.IX Item "Coercion tables"
+Moose::Util::TypeConstraints
+.SH "VERSION CONTROL"
+.IX Header "VERSION CONTROL"
+This module is maintained using git. You can get the latest version from
+<http://github.com/nothingmuch/data\-stream\-bulk/>.
+.SH "AUTHOR"
+.IX Header "AUTHOR"
+Yuval Kogman <nothingmuch@woobling.org>
+.SH "COPYRIGHT"
+.IX Header "COPYRIGHT"
+.Vb 3
+\& Copyright (c) 2008 Yuval Kogman. All rights reserved
+\& This program is free software; you can redistribute
+\& it and/or modify it under the same terms as Perl itself.
+.Ve
projects / catagits/Gitalist.git / blobdiff