On 13th of April, Tom Lane committed patch:
Provide moving-aggregate support for a bunch of numerical aggregates. First installment of the promised moving-aggregate support in built-in aggregates: count(), sum(), avg(), stddev() and variance() for assorted datatypes, though not for float4/float8. In passing, remove a 2001-vintage kluge in interval_accum(): interval array elements have been properly aligned since around 2003, but nobody remembered to take out this workaround. Also, fix a thinko in the opr_sanity tests for moving-aggregate catalog entries. David Rowley and Florian Pflug, reviewed by Dean Rasheed
On the same day he also committed:
Provide moving-aggregate support for boolean aggregates. David Rowley and Florian Pflug, reviewed by Dean Rasheed
Continue reading Waiting for 9.4 – Provide moving-aggregate support for a bunch of aggregates.