GTIN14 support for contrib/isn

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GTIN14 support for contrib/isn

Michael Kefeder
Hello hackers,

For a project of ours we need GTIN14 data type support. The isn
extension already supports EAN13, and a '0' prefixed EAN13 is a valid
GTIN14. The leftmost "new" 14th digit is a packaging level indicator
which we need (= using EAN13 and faking a leading 0 in output doesn't
cut it).

Looking at the code I saw every format that isn-extension supports is
stored as an EAN13. Theoretically that can be changed to be GTIN14, but
that would mean quite a lot of rewrite I feared, so I chose to code only
GTIN14 I/O separetely to not interfere with any existing conversion
magic. This yields an easier to understand patch and doesn't touch
existing functionality. However it introduces redundancy to a certain
extent.

Find my patch attached. Please let me know if there are things that need
changes, I'll do my best to get GTIN support into postgresql.

thanks in advance
  mike

gtin14.patch (24K) Download Attachment
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Re: GTIN14 support for contrib/isn

Tom Lane-2
Michael Kefeder <[hidden email]> writes:
> For a project of ours we need GTIN14 data type support.

Hm, what is that and where would a reviewer find the specification for it?

> Looking at the code I saw every format that isn-extension supports is
> stored as an EAN13. Theoretically that can be changed to be GTIN14, but
> that would mean quite a lot of rewrite I feared, so I chose to code only
> GTIN14 I/O separetely to not interfere with any existing conversion
> magic. This yields an easier to understand patch and doesn't touch
> existing functionality. However it introduces redundancy to a certain
> extent.

Yeah, you certainly don't get to change the on-disk format of the existing
types, unfortunately.  Not sure what the least messy way of dealing with
that is.  I guess we do want this to be part of contrib/isn rather than
an independent module, if there are sane datatype conversions with the
existing isn types.

> Find my patch attached. Please let me know if there are things that need
> changes, I'll do my best to get GTIN support into postgresql.

Well, two comments immediately:

* where's the documentation changes?

* simply editing the .sql file in-place is not acceptable; that breaks
the versioning conventions for extensions, and leaves users with no
easy upgrade path.  What you need to do is create a version upgrade
script that adds the new objects.  For examples look for other recent
patches that have added features to contrib modules, eg

https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=eb6f29141bed9dc95cb473614c30f470ef980705

Also, I'm afraid you've pretty much missed the deadline to get this
into PG v12; we've already got more timely-submitted patches than
we're likely to be able to finish reviewing.  Please add it to the
first v13 commit fest,

https://commitfest.postgresql.org/23/

so that we don't forget about it when the time does come to look at it.

                        regards, tom lane

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Re: GTIN14 support for contrib/isn

Michael Kefeder

Am 15.03.19 um 17:27 schrieb Tom Lane:
> Michael Kefeder <[hidden email]> writes:
>> For a project of ours we need GTIN14 data type support.
>
> Hm, what is that and where would a reviewer find the specification for it?
>
specs are from GS1 here https://www.gs1.org/standards/id-keys/gtin
side-note EAN13 is actually called GTIN-13 now. Wikipedia has a quick
overview https://en.wikipedia.org/wiki/Global_Trade_Item_Number

>> Looking at the code I saw every format that isn-extension supports is
>> stored as an EAN13. Theoretically that can be changed to be GTIN14, but
>> that would mean quite a lot of rewrite I feared, so I chose to code only
>> GTIN14 I/O separetely to not interfere with any existing conversion
>> magic. This yields an easier to understand patch and doesn't touch
>> existing functionality. However it introduces redundancy to a certain
>> extent.
>
> Yeah, you certainly don't get to change the on-disk format of the existing
> types, unfortunately.  Not sure what the least messy way of dealing with
> that is.  I guess we do want this to be part of contrib/isn rather than
> an independent module, if there are sane datatype conversions with the
> existing isn types.
>
the on-disk format does not change (it would support even longer codes
it's just an integer where one bit is used for valid/invalid flag, did
not touch that at all). Putting GTIN14 in isn makes sense I find and is
back/forward compatible.

>> Find my patch attached. Please let me know if there are things that need
>> changes, I'll do my best to get GTIN support into postgresql.
>
> Well, two comments immediately:
>
> * where's the documentation changes?
>
> * simply editing the .sql file in-place is not acceptable; that breaks
> the versioning conventions for extensions, and leaves users with no
> easy upgrade path.  What you need to do is create a version upgrade
> script that adds the new objects.  For examples look for other recent
> patches that have added features to contrib modules, eg
>
> https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=eb6f29141bed9dc95cb473614c30f470ef980705
>
> Also, I'm afraid you've pretty much missed the deadline to get this
> into PG v12; we've already got more timely-submitted patches than
> we're likely to be able to finish reviewing.  Please add it to the
> first v13 commit fest,
>
> https://commitfest.postgresql.org/23/
>
> so that we don't forget about it when the time does come to look at it.
>
> regards, tom lane
>

thanks for the feedback! will do mentioned documentation changes and
create a separate upgrade sql file. Making it into v13 is fine by me.

br
  mike