…astic#55559)

Rounding dates on a shard that contains a daylight savings time transition
is currently something like 1400% slower than when a shard contains dates
only on one side of the DST transition. And it makes a ton of short lived
garbage. This replaces that implementation with one that benchmarks to
having around 30% overhead instead of the 1400%. And it doesn't generate
any garbage per search hit.

Some background:
There are two ways to round in ES:
* Round to the nearest time unit (Day/Hour/Week/Month/etc)
* Round to the nearest time *interval* (3 days/2 weeks/etc)

I'm only optimizing the first one in this change and plan to do the second
in a follow up. It turns out that rounding to the nearest unit really *is*
two problems: when the unit rounds to midnight (day/week/month/year) and
when it doesn't (hour/minute/second). Rounding to midnight is consistently
about 25% faster and rounding to individual hour or minutes.

This optimization relies on being able to *usually* figure out what the
minimum and maximum dates are on the shard. This is similar to an existing
optimization where we rewrite time zones that aren't fixed
(think America/New_York and its daylight savings time transitions) into
fixed time zones so long as there isn't a daylight savings time transition
on the shard (UTC-5 or UTC-4 for America/New_York). Once I implement
time interval rounding the time zone rewriting optimization *should* no
longer be needed.

This optimization doesn't come into play for `composite` or
`auto_date_histogram` aggs because neither have been migrated to the new
`DATE` `ValuesSourceType` which is where that range lookup happens. When
they are they will be able to pick up the optimization without much work.
I expect this to be substantial for `auto_date_histogram` but less so for
`composite` because it deals with fewer values.

Note: My 30% overhead figure comes from small numbers of daylight savings
time transitions. That overhead gets higher when there are more
transitions in logarithmic fashion. When there are two thousand years
worth of transitions my algorithm ends up being 250% slower than rounding
without a time zone, but java time is 47000% slower at that point,
allocating memory as fast as it possibly can.

…5559) (#56334)

Rounding dates on a shard that contains a daylight savings time transition
is currently something like 1400% slower than when a shard contains dates
only on one side of the DST transition. And it makes a ton of short lived
garbage. This replaces that implementation with one that benchmarks to
having around 30% overhead instead of the 1400%. And it doesn't generate
any garbage per search hit.

Some background:
There are two ways to round in ES:
* Round to the nearest time unit (Day/Hour/Week/Month/etc)
* Round to the nearest time *interval* (3 days/2 weeks/etc)

I'm only optimizing the first one in this change and plan to do the second
in a follow up. It turns out that rounding to the nearest unit really *is*
two problems: when the unit rounds to midnight (day/week/month/year) and
when it doesn't (hour/minute/second). Rounding to midnight is consistently
about 25% faster and rounding to individual hour or minutes.

This optimization relies on being able to *usually* figure out what the
minimum and maximum dates are on the shard. This is similar to an existing
optimization where we rewrite time zones that aren't fixed
(think America/New_York and its daylight savings time transitions) into
fixed time zones so long as there isn't a daylight savings time transition
on the shard (UTC-5 or UTC-4 for America/New_York). Once I implement
time interval rounding the time zone rewriting optimization *should* no
longer be needed.

This optimization doesn't come into play for `composite` or
`auto_date_histogram` aggs because neither have been migrated to the new
`DATE` `ValuesSourceType` which is where that range lookup happens. When
they are they will be able to pick up the optimization without much work.
I expect this to be substantial for `auto_date_histogram` but less so for
`composite` because it deals with fewer values.

Note: My 30% overhead figure comes from small numbers of daylight savings
time transitions. That overhead gets higher when there are more
transitions in logarithmic fashion. When there are two thousand years
worth of transitions my algorithm ends up being 250% slower than rounding
without a time zone, but java time is 47000% slower at that point,
allocating memory as fast as it possibly can.

When an index spans a daylight savings time transition we can't use our
optimization that rewrites the requested time zone to a fixed time zone
and instead we used to fall back to a java.util.time based rounding
implementation. In elastic#55559 we optimized "time unit" rounding. This
optimizes "time interval" rounding.

The java.util.time based implementation is about 1650% slower than the
rounding implementation for a fixed time zone. This replaces it with a
similar optimization that is only about 30% slower than the fixed time
zone. The java.util.time implementation allocates a ton of short lived
objects but the optimized implementation doesn't. So it *might* end up
being faster than the microbenchmarks imply.

This wires `auto_date_histogram` into the rounding optimization that I
built in elastic#55559. This is should significantly speed up any
`auto_date_histogram`s with `time_zone`s on them.

When an index spans a daylight savings time transition we can't use our
optimization that rewrites the requested time zone to a fixed time zone
and instead we used to fall back to a java.util.time based rounding
implementation. In #55559 we optimized "time unit" rounding. This
optimizes "time interval" rounding.

The java.util.time based implementation is about 1650% slower than the
rounding implementation for a fixed time zone. This replaces it with a
similar optimization that is only about 30% slower than the fixed time
zone. The java.util.time implementation allocates a ton of short lived
objects but the optimized implementation doesn't. So it *might* end up
being faster than the microbenchmarks imply.

When an index spans a daylight savings time transition we can't use our
optimization that rewrites the requested time zone to a fixed time zone
and instead we used to fall back to a java.util.time based rounding
implementation. In elastic#55559 we optimized "time unit" rounding. This
optimizes "time interval" rounding.

The java.util.time based implementation is about 1650% slower than the
rounding implementation for a fixed time zone. This replaces it with a
similar optimization that is only about 30% slower than the fixed time
zone. The java.util.time implementation allocates a ton of short lived
objects but the optimized implementation doesn't. So it *might* end up
being faster than the microbenchmarks imply.

When an index spans a daylight savings time transition we can't use our
optimization that rewrites the requested time zone to a fixed time zone
and instead we used to fall back to a java.util.time based rounding
implementation. In #55559 we optimized "time unit" rounding. This
optimizes "time interval" rounding.

The java.util.time based implementation is about 1650% slower than the
rounding implementation for a fixed time zone. This replaces it with a
similar optimization that is only about 30% slower than the fixed time
zone. The java.util.time implementation allocates a ton of short lived
objects but the optimized implementation doesn't. So it *might* end up
being faster than the microbenchmarks imply.

This wires `auto_date_histogram` into the rounding optimization that I
built in #55559. This is should significantly speed up any
`auto_date_histogram`s with `time_zone`s on them.

This wires `auto_date_histogram` into the rounding optimization that I
built in elastic#55559. This is should significantly speed up any
`auto_date_histogram`s with `time_zone`s on them.

This wires `auto_date_histogram` into the rounding optimization that I
built in #55559. This is should significantly speed up any
`auto_date_histogram`s with `time_zone`s on them.