datetime value units

[robambalu]

Hey, for the datetime type it looks like perspective only supports sending datetime as epoch time in milliseconds.
Our systems can generate time in various units ( seconds, millis, micros, etc ) so we find ourselves converting every single datetime data event on the front end into millis before pushing into perspective. Is there a way to control the expected units of a datetime column, and if not is there an appetite to add support for it?

Thanks

• Rob

[sc1f]

From 0.10.0 onwards you should be able to create an expression column to do the conversion within perspective:

// datetime column
datetime(“seconds_timestamp” * 1000)

In this case seconds_timestamp is a float column, and the output of the expression is a datetime.

On Jul 30, 2021, at 11:08 PM, robambalu @.***> wrote:



Hey, for the datetime type it looks like perspective only supports sending datetime as epoch time in milliseconds. Our systems can generate time in various units ( seconds, millis, micros, etc ) so we find ourselves converting every single datetime data event on the front end into millis before pushing into perspective. Is there a way to control the expected units of a datetime column, and if not is there an appetite to add support for it?

Thanks

• Rob

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[sc1f]

A handy GIF of the fix in action:

If you have many columns that need the conversion, you can auto-generate the expressions and apply them to the viewer/PerspectiveWidget using the expressions attribute, which takes a list of string expressions.

[robambalu]

Understood, thank you for that. Do you think it make sense to avoid the need for this type of conversation and support different datetime units when defining the schema? Similar to how arrow has it

From: Jun Tan @.> Sent: Wednesday, August 4, 2021 12:16 PM To: finos/perspective @.> Cc: Ambalu, Robert @.>; Author @.> Subject: Re: [finos/perspective] datetime value units (#1500)

A handy GIF of the fix in action:

[dtconvert]https://urldefense.com/v3/__https:/user-images.githubusercontent.com/13220267/128216675-37e43fa4-ce32-4545-9e8f-d05ce77fce3d.gif__;!!K_TC0FI_KA!9xeeYYc_ltcz5HexCGFAFGN6nEFvcY2qNe27o9pO18fMfVfQss2vu501yUrSym_7gggTQQ$

If you have many columns that need the conversion, you can auto-generate the expressions and apply them to the viewer/PerspectiveWidget using the expressions attribute, which takes a list of string expressions.

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[texodus]

@robambalu Not avoid per se (the conversions are useful in themselves), but the we're working on a plan to replace parts of Perspective's internal data structures with Arrow directly, like the columnar store itself, in which case Perspective would support all (or all useful) Arrow data types.

[nickroci]

FYI you can get around this by creating arrow table bytes and passing them into perspective (can choose precision in arrow conversion to dt), I find it much faster and more reliable, especially compare to df