[postgis-users] Bytea data type and its application and uses

[Giuseppe Broccolo]

Hi Shao,

I don't know how PowerBI works frankly. My idea is that they do not support
direct access to bytea data, so maybe you need to put something in the
middle to decode/encode.

Giuseppe.

Il giorno ven 18 set 2020 alle ore 11:17 Shaozhong SHI <
shishaozhong at gmail.com> ha scritto:

> Hi,  Giuseppe,
>
> Thank you for your reply.
>
> We know those literature.  The issue is that there is a lack of working
> examples to demonstrate its use.
>
> Let's say that people are using PowerBI, Graphic Packages, GIS application
> users and etc.  Can these packages access and retrieve image data (Bytea)
> from PostGIS?
>
> Regards,
>
> Shao
>
> On Fri, 18 Sep 2020 at 11:07, Giuseppe Broccolo <g.broccolo.7 at gmail.com>
> wrote:
>
>> Hi Shao,
>>
>> What do you need to store, more specifically? Since this is a PostGIS
>> related thread, is it about raster data, etc.?
>>
>> Anyway, as a general info about binary data: there are two general ways
>> to insert binaries into a PostgreSQL database, the hex format and the
>> escape format. I attach here the reference:
>> https://www.postgresql.org/docs/12/datatype-binary.html
>>
>> As a personal experience, I used the hexadecimal format: the idea is to
>> convert the binary blob into hex digits representation, where one digit
>> represents an hex nibble, and each byte of the binary blob is converted
>> into two digits, with the most significant nibble first. Then the hex
>> digits can be inserted as you would insert a string, preceded with the
>> char  \x.
>>
>> Depending on what you use at the application side, there are different
>> ways of encoding a binary blob into hex format. If you want to try
>> something "manually" from a file using psql, try with utilities like
>> hexdump, keeping in mind that the binary content in the file is encoded
>> using the platform's endianness, i.e. with the most significant nibble put
>> for first or for last (check this from your OS).
>>
>> Hope it helped,
>> Giuseppe.
>>
>> Il giorno gio 17 set 2020 alle ore 20:58 Shaozhong SHI <
>> shishaozhong at gmail.com> ha scritto:
>>
>>> We can see various publications on the Bytea data type.
>>>
>>> However, it is difficult to find practical examples of how to use it.
>>>
>>> Anyone knows?
>>>
>>> Regards,
>>>
>>> Shao
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>>> https://lists.osgeo.org/mailman/listinfo/postgis-users
>>
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