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

[Giuseppe Broccolo]

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
> _______________________________________________
> postgis-users mailing list
> postgis-users at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/postgis-users
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