Add functions for scaling intervals #26
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tfausak
commented
Sep 8, 2025
| -- >>> scale 0.6 (MkInterval 0 0 1) -- rounds up | ||
| -- Just (MkInterval {months = 0, days = 0, microseconds = 1}) | ||
| -- | ||
| -- Fractional days are converted into microseconds, assuming 24 hours per day. |
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This behavior is a bit strange, but it's what PostgreSQL does:
postgres=# select interval '1 day' * 0.5;
?column?
----------
12:00:00
(1 row)
tfausak
commented
Sep 8, 2025
| -- | ||
| -- Fractional months are converted into days, assuming 30 days per month. If | ||
| -- this conversion produces fractional days, those are converted into | ||
| -- microseconds. |
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Similarly:
postgres=# select interval '1 month' * 0.05;
?column?
----------------
1 day 12:00:00
(1 row)
tfausak
commented
Sep 8, 2025
| -- Just (MkInterval {months = 0, days = 1, microseconds = 43200000000}) | ||
| -- | ||
| -- Returns 'Nothing' if any component would overflow. See 'scaleSaturating' for | ||
| -- a version that uses saturating arithmetic instead. |
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PostgreSQL errors out if an interval would overflow:
postgres=# select interval '46341 days' * 46341;
ERROR: interval out of range
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I added
negatein #21, but it can be generalized into arbitrary scaling. And then it's simplynegate = scale (-1).