Add timestamp and timezone management documentation #10036
Closed
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
✅ Deploy Preview for meta-velox canceled.
|
|
Cc: @PHILO-HE |
|
@pedroerp has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
mbasmanova
approved these changes
Jun 5, 2024
velox/docs/develop/timestamp.rst
Outdated
| reading of a wall clock and a calendar, e.g, ``2024-04-09 18:25:00``. Note that | ||
| a TIMESTAMP does not represent an absolute point in time, as the exact same | ||
| wall clock time may be read in different instants in time depending on where | ||
| one is situated on earth. For example, ``2024-04-09 18:25:00`` in California |
There was a problem hiding this comment.
nit: wondering if earth should be Earth
velox/docs/develop/timestamp.rst
Outdated
| a TIMESTAMP does not represent an absolute point in time, as the exact same | ||
| wall clock time may be read in different instants in time depending on where | ||
| one is situated on earth. For example, ``2024-04-09 18:25:00`` in California | ||
| and in China were perceived at different absolute points in time, about 15h |
velox/docs/develop/timestamp.rst
Outdated
| * While “seconds” can be negative to represent time before ``1970-01-01 | ||
| 00:00:00``, “nanoseconds” are always positive. | ||
|
|
||
| * Engines like Presto and Spark only support milliseconds precision, so |
There was a problem hiding this comment.
I believe Spark supports at least microseconds precision.
velox/docs/develop/timestamp.rst
Outdated
| 00:00:00``, “nanoseconds” are always positive. | ||
|
|
||
| * Engines like Presto and Spark only support milliseconds precision, so | ||
| naturally “nanoseconds” are zeroed. |
There was a problem hiding this comment.
Nanoseconds are used even with millisecond precision.
velox/docs/develop/timestamp.rst
Outdated
| TimestampWithTimezones are serialized, for example. | ||
|
|
||
| **TimestampWithTimezone:** To represent an absolute point in time, Velox provides | ||
| the `TimestampWithTimezone class <https://github.com/facebookincubator/velox/blob/main/velox/functions/prestosql/types/TimestampWithTimeZoneType.h>`_. |
There was a problem hiding this comment.
I don't think there is a TimestampWithTimezone class.
There was a problem hiding this comment.
well, it's an alias:
I'll rephrase.
velox/docs/develop/timestamp.rst
Outdated
|
|
||
| **TimestampWithTimezone:** To represent an absolute point in time, Velox provides | ||
| the `TimestampWithTimezone class <https://github.com/facebookincubator/velox/blob/main/velox/functions/prestosql/types/TimestampWithTimeZoneType.h>`_. | ||
| This class implements the TIMESTAMP WITH TIMEZONE sql semantic discussed above, |
velox/docs/develop/timestamp.rst
Outdated
| **TimestampWithTimezone:** To represent an absolute point in time, Velox provides | ||
| the `TimestampWithTimezone class <https://github.com/facebookincubator/velox/blob/main/velox/functions/prestosql/types/TimestampWithTimeZoneType.h>`_. | ||
| This class implements the TIMESTAMP WITH TIMEZONE sql semantic discussed above, | ||
| and was based on Presto’s implementation - therefore only supporting |
velox/docs/develop/timestamp.rst
Outdated
| millisecond-precision. | ||
|
|
||
| TimestampWithTimezone physically packs two integers in a single 64 word, using | ||
| 12 bits for timezone ID, and 52 for a millisecond-precision timestamp. |
|
|
||
| .. code-block:: bash | ||
|
|
||
| $ rpm -qa | grep tzdata |
There was a problem hiding this comment.
I tried this command on my Mac, but it didn't print anything.
There was a problem hiding this comment.
this is for linux; added to the text to clarify
zacw7
approved these changes
Jun 5, 2024
velox/docs/develop/timestamp.rst
Outdated
|
|
||
| To represent absolute points in time, SQL defines a TIMESTAMP WITH TIMEZONE | ||
| type, which conceptually represents a pair of a wall time and calendar read | ||
| (say, ``2024-04-09 18:25:00``), and a timezone (``PST``, or |
There was a problem hiding this comment.
April should be in PDT instead of PST at America/Los_Angeles. Or we can just put PT here.
velox/docs/develop/timestamp.rst
Outdated
|
|
||
| .. code-block:: sql | ||
|
|
||
| presto:de> select typeof(TIMESTAMP '1970-01-01 00:00:00'); |
There was a problem hiding this comment.
Let's omit the presto:de part? Should we keep the format of the examples consistent as https://facebookincubator.github.io/velox/functions/presto/conversion.html#cast-to-timestamp
There was a problem hiding this comment.
Nice! That's better
Adding a new documentation page to describe details of management of timestamp, timezone and conversions in Velox.
8f8c11e to
96daf21
Compare
|
@pedroerp has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator. |
|
Conbench analyzed the 1 benchmark run on commit There were no benchmark performance regressions. 🎉 The full Conbench report has more details. |
Joe-Abraham
pushed a commit
to Joe-Abraham/velox
that referenced
this pull request
Jun 7, 2024
…r#10036) Summary: Adding a new documentation page to describe details of management of timestamps, timezone and conversions in Velox. Pull Request resolved: facebookincubator#10036 Reviewed By: mbasmanova, zacw7 Differential Revision: D58172617 Pulled By: pedroerp fbshipit-source-id: a8fc2e5a78bd65bf587b65e3296ef3c27f23da28
Joe-Abraham
pushed a commit
to Joe-Abraham/velox
that referenced
this pull request
Jun 7, 2024
…r#10036) Summary: Adding a new documentation page to describe details of management of timestamps, timezone and conversions in Velox. Pull Request resolved: facebookincubator#10036 Reviewed By: mbasmanova, zacw7 Differential Revision: D58172617 Pulled By: pedroerp fbshipit-source-id: a8fc2e5a78bd65bf587b65e3296ef3c27f23da28
deepashreeraghu
pushed a commit
to deepashreeraghu/velox
that referenced
this pull request
Jun 13, 2024
…r#10036) Summary: Adding a new documentation page to describe details of management of timestamps, timezone and conversions in Velox. Pull Request resolved: facebookincubator#10036 Reviewed By: mbasmanova, zacw7 Differential Revision: D58172617 Pulled By: pedroerp fbshipit-source-id: a8fc2e5a78bd65bf587b65e3296ef3c27f23da28
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Adding a new documentation page to describe details of management of timestamps, timezone and conversions in Velox.