e: Running/cumulative count using windows

> test=*# select extract (year from signup_date)::text || '/' ||
extract(month from signup_date)::text, count(email_address),
sum(count(email_address)) over (ROWS UNBOUNDED PRECEDING) from test
group by 1 order by 1;

Have searched the manual and been unable to find reference to the
commands 'unbounded' and 'preceding'; can someone please advise where
to read about these commands?

On 12/09/2013, pgsql-general-owner@postgresql.org
<pgsql-general-owner@postgresql.org> wrote:
> Message Digest
> Volume 1 : Issue 12450 : "mime" Format
>
> Messages in this Issue:
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>   Re: Call for design: PostgreSQL mugs
>   Re: Call for design: PostgreSQL mugs
>   problem with query
>   Re: problem with query
>   Re: problem with query
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>   Re: problem with query
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>   Re: problem with query
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>   Re: problem with query
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