Is it possible to add entries to the bibliography based on keyword using Biblatex/Biber and within the document code?

Question

I would like to print a bibliography which includes all entries with a certain keyword (and possibly some additional entries).

I know that I can filter by keyword when I print the bibliography using

\printbibliography[keyword=<keyword>]

but this will only print entries which I have cited. I could, of course, use

\nocite{*}

to add all entries to the bibliography and then print just those I want.

However, this will make my .bbl file huge as my database is enormous.

Another possibility is to use Biber or another tool to prepare a document-specific .bib file containing only those entries with the keyword. However, this would need to be recreated if additional entries with the keyword are added to my main database files.

Here's an MWE to play with, annotated to indicate the way I'd like it to work ;), and the disadvantages of the way it (almost) works.

The issue of excluding explicitly cited entries is less of an issue for me. The thing I'd really like to work around is adding the entire database contents to the .bbl.

\RequirePackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{new-stuff,
    author          =   {Watt, Brian},
    title           =   {Happy Times with Penguins},
    publisher       =   {Harvard University Press},
    address         =   {Cambridge, MA},
    year            =   1995,
    pagination      =   {section},
    keywords        =   {happy}}
@book{den-coll,
  author                =   {Till, Jr., Dennis E.},
    booktitle           =   {Penguin Land and Further North: Human Influence},
    title               =   {Penguin Land and Further North: Human Influence},
    publisher           =   {Oxford University Press},
    year                =   2008,
    address             =   {Oxford and New York},
    keywords            =   {penguin, human}}
@book{old-stuff,
  author                =   {Harvey, Jr., Dennis E.},
    booktitle           =   {Penguin Land and Further North: Human Influence},
    title               =   {Penguin Land and Further North: Human Influence},
    publisher           =   {Someone \& Daughters},
    year                =   1567,
    address             =   {Oxford},
    bookpagination      =   {paragraph},
    keywords            =   {penguin}}
\end{filecontents}
\documentclass{article}
\usepackage[defernumbers=true]{biblatex}
\bibliography{\jobname}
\begin{document}

\cite{old-stuff}

% what I would like to work
% \nocite[keyword=happy]
% \printbibliography

% what does work - except that \cite{old-stuff} is ignored and, more importantly, den-coll is added to the .bbl
\nocite{*}
\printbibliography[keyword=happy]

\end{document}

As far as I know, the keyword filtering can only work if the entry is actually in the .bbl file, otherwise biblatex has no way to know about the presence or absence of a keyword. Using Biber, we can simply ignore all entries without (or with) a certain keyword (see entrynull), of course previous \cite commands cannot help us here. — moewe, Aug 05 '15 at 17:33
See also \nocite{*} for single bibdatasources with biblatex/biber and the corresponding biblatex bug report #228. — moewe, Aug 05 '15 at 17:35
What about using the strategy used in this question http://tex.stackexchange.com/q/244620/16895? where you use a first round of computation with \cite{*} and then a second round where you include a no cite for the entries with the appropriate keywords. — Guido, Aug 05 '15 at 17:40
@Guido The first round is going to take forever. \cite{*} will produce an enormous .bbl, just as \nocite{*} would. (It would let me then include additional entries, so it would have that advantage. But the main downside would be the same.) — cfr, Aug 05 '15 at 20:55
@moewe I was afraid of that. And, actually, even the feature requested wouldn't help. I need to extract entries from .bib files and I don't want to end up with a .bbl with 3,000+ entries just so I can filter out a couple of handfuls. I would think that keyword filtering would be very useful at the document level but perhaps I'm wrong and there's just no real demand for it. — cfr, Aug 05 '15 at 21:02
When I made the feature request I was thinking about filtering options just the way \printbibliography and friends can be filtered; I would have thought this would be right up your street in this case. Of course this is an academic discussion since PLK explained that this is nearly impossible considering the way Biber and biblatex work. — moewe, Aug 06 '15 at 04:37
@moewe I thought the feature request was for \nocite filtering by bib resource rather than by content of a particular field i.e. at the resource rather than entry level? As you say, the question is unfortunately hypothetical in any case. — cfr, Aug 06 '15 at 13:38
First and foremost yes, when I asked, however, I thought of (and hoped for) something like the filtering options for \printbibliography (That's why I wrote "It might also be useful to \nocite only entries with a particular keyword etc..") Alas, in view of the technical limitations this venture does not seem to have been born under a lucky star. — moewe, Aug 06 '15 at 14:45

PLK · Accepted Answer · 2019-09-11T13:44:41.340

Update: This is now possible with biber 2.14/biblatex 3.14, both in their respective development folders on github [1][2]:

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@book{new-stuff,
    author          =   {Watt, Brian},
    title           =   {Happy Times with Penguins},
    publisher       =   {Harvard University Press},
    address         =   {Cambridge, MA},
    year            =   1995,
    pagination      =   {section},
    keywords        =   {happy}}
@book{den-coll,
  author                =   {Till, Jr., Dennis E.},
    booktitle           =   {Penguin Land and Further North: Human Influence},
    title               =   {Penguin Land and Further North: Human Influence},
    publisher           =   {Oxford University Press},
    year                =   2008,
    address             =   {Oxford and New York},
    keywords            =   {penguin, human}}
@book{old-stuff,
  author                =   {Harvey, Jr., Dennis E.},
    booktitle           =   {Penguin Land and Further North: Human Influence},
    title               =   {Penguin Land and Further North: Human Influence},
    publisher           =   {Someone \& Daughters},
    year                =   1567,
    address             =   {Oxford},
    bookpagination      =   {paragraph},
    keywords            =   {penguin}}
\end{filecontents*}

\usepackage[defernumbers=true]{biblatex}
\addbibresource{\jobname.bib}
\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[nocited, final]
      \step[fieldsource=keywords, notmatch=happy, final]
      \step[entrynull]
    }
  }
}

\begin{document}

\cite{old-stuff}

\nocite{*}
\printbibliography

\end{document}

This removes entries during parsing the data sources which are \nocited or which don't have the keyword.

This used to be impossible but biber for quite some time now has had access to the refsection information on entry key origins when parsing the data sources which makes some things now possible. — PLK, Sep 11 '19 at 13:46
Excellent! Thank you so much. (Not tested yet - currently struggling with TL2019 updating.) — cfr, Sep 29 '19 at 18:40

score 3 · Answer 2 · answered Sep 03 '17 at 12:33

This is an old question, and it doesn't look like there is a really satisfactory answer. But here's a solution that involves a perl script just for fun.

Remember to run it with pdflatex --enable-write18.

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents*}{allentries.bib}
@book{new-stuff,
    author          =   {Watt, Brian},
    title           =   {Happy Times with Penguins},
    publisher       =   {Harvard University Press},
    address         =   {Cambridge, MA},
    year            =   1995,
    pagination      =   {section},
    keywords        =   {happy}}
@book{den-coll,
  author                =   {Till, Jr., Dennis E.},
    booktitle           =   {Penguin Land and Further North: Human Influence},
    title               =   {Penguin Land and Further North: Human Influence},
    publisher           =   {Oxford University Press},
    year                =   2008,
    address             =   {Oxford and New York},
    keywords            =   {penguin, human}}
@book{old-stuff,
  author                =   {Harvey, Jr., Dennis E.},
    booktitle           =   {Penguin Land and Further North: Human Influence},
    title               =   {Penguin Land and Further North: Human Influence},
    publisher           =   {Someone \& Daughters},
    year                =   1567,
    address             =   {Oxford},
    bookpagination      =   {paragraph},
    keywords            =   {penguin}}
\end{filecontents*}
\begin{filecontents*}{citekeyword.pl}
use strict;
use warnings;
use Text::BibTeX;
my $keyword = "happy"; # set keyword here
my $bibfile = Text::BibTeX::File->new("allentries.bib");
my $keywordcitefile = "keywordcites.tex";
open(my $fh, '>', $keywordcitefile) or
    die "Could not open file '$keywordcitefile' $!";
my $keywords;
my $entry;
while ($entry = Text::BibTeX::Entry->new($bibfile)) {
    next unless $entry->parse_ok;
    if ($entry->get("keywords")) {
        $keywords = "," . $entry->get("keywords") . ",";
        if ($keywords =~ /,$keyword,/) {
            print $fh "\\nocite{" . $entry->key . "}\n";
        }
    }
}
close $fh;
\end{filecontents*}
\immediate\write18{/usr/bin/perl citekeyword.pl}
\usepackage[defernumbers=true]{biblatex}
\addbibresource{allentries.bib}
\pagestyle{empty}
\begin{document}
\input{keywordcites.tex}
\cite{old-stuff}
\printbibliography
\end{document}

Very nice! I hope you don't mind that I won't accept your answer, as it really doesn't answer the question. As you mentioned, there probably isn't a satisfactory answer. But definitely more than worth an up-vote :-). — cfr, Sep 03 '17 at 13:45
haha no worries. It is technically within the document code, just not what you hoped for. ;) — David Purton, Sep 03 '17 at 14:26
Yes, it is a bit unfair. It is just that if it stays open, well, who knows whether it might get the perfect answer in a couple of decades or so? Some descendant of Biber/Biblatex, perhaps .... Of course, the world may end before then, but at least I can dream :-). — cfr, Sep 03 '17 at 20:09
Not even 2 decades - only 2 years! I thought you might want to see the answer from PLK above. — cfr, Sep 29 '19 at 18:41

Is it possible to add entries to the bibliography based on keyword using Biblatex/Biber and within the document code?

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