Optimize Timestamp Formatting #15039
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pettyjamesm
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Compute exact size StringBuilders and avoid using String.format to produce timestamp string representations.
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martint
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Nov 16, 2022
| // comparable to format("%0" + precision + "d", scaledFraction); | ||
| for (int i = 0; i < precision; i++) { | ||
| long temp = scaledFraction / 10; | ||
| int digit = (int) (scaledFraction - (temp * 10)); |
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Why not scaledFraction % 10 ? Is there a measurable performance difference?
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I didn't specifically measure it, this is a variation on the logic inside of Long.toString so I presume it was implemented that way on purpose.
(Long.toString resolves two decimal digits per iteration and therefore also uses lookup tables to convert to char instead of (char)('0' + digit), but that was definitely overkill for this scenario).
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Description
Optimize
SqlTimestampandSqlTimestampWithTimeZonestring formatting by calculating the exact required buffer size and avoiding a call toString.format("%0" + precision + "d", ...)on a per-row basis.Non-technical explanation
No non-technical explanation should be necessary since this is an internal implementation detail.
Release notes
(x) This is not user-visible or docs only and no release notes are required.
( ) Release notes are required, please propose a release note for me.
( ) Release notes are required, with the following suggested text: