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From: Daniel Verite <[email protected]>
To: Andy Hartman <[email protected]>
Cc: [email protected]
Subject: Re: Display Bytea field
Date: Fri, 10 Jan 2025 13:49:40 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAEZv3copeUd7mNf98qxBtkqqW=g3MtCJe62jdMEEzFC4M=-+4A@mail.gmail.com>

	Andy Hartman wrote:

> How thru a simple query can I make sure data matches and I can display it
> 
> On Thu, Jan 9, 2025 at 3:16 PM Andy Hartman <[email protected]> wrote:
> 
> > I have migrated over a Table from Mssql that had an Image column I now
> > have it in Postgres

Within psql, the bytea field can be copied into a large object
with lo_from_bytea() [1], and then the large object exported
into a local file with \lo_export [2]

Alternatively, you could compare image checksums before and
after moving them into postgres. The advantage is that you
don't need to export or view any file, and you compare globally
all your images. If the checksums are identical, the data are identical.
On the MSSQL side, checksums can be computed with hashbytes()
as suggested in this stackoverflow answer: [3]
On the postgres side, use functions like md5() or sha256()
directly on the bytea column.


[1] https://www.postgresql.org/docs/current/lo-funcs.html

[2]
https://www.postgresql.org/docs/current/app-psql.html#APP-PSQL-META-COMMAND-LO-EXPORT

[3] https://stackoverflow.com/a/33256990/


Best regards,
-- 
Daniel Vérité
https://postgresql.verite.pro/
Twitter: @DanielVerite

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