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Editorial Team
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Asked: 2026-05-21T13:52:30+00:00

I was playing with pg_size_pretty() and I’ve discovered that when I pass it a

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I was playing with pg_size_pretty() and I’ve discovered that when I pass it a great value it starts to return negative value.
This is my test:

select pg_size_pretty(9223370000000000000); -- "8388606 TB"
select pg_size_pretty(9223371000000000000); -- "8388607 TB"
select pg_size_pretty(9223372000000000000); -- "-8388607 TB"

Can you explain me why?
Thanks.

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1 Answer

  1. Editorial Team

    The highest signed 64 bit int is 922337203685477587. That’s but a tiny bit more than the number in question. Surely there’s an overflow somewhere in pg_size_pretty.

    Based on the code mentioned in a comment, pg_size_pretty is attempting to round the number and does so using an intermediary value that’s larger than the max signed 64-bit int. 9223372000000000000 + 1024*1024*1024*1024/2 = 9223372549755813888, which is larger than 922337203685477587.

    Update: Added second paragraph and clarified that the overflow isn’t in the caller.

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