PostgreSQL \lo_import and how to get the resulting OID into an UPDATE command? - batch-file

Question

I'm working with Postgres 9.0, and I have an application where I need to insert images into the remote server. So I use:
"C:\Program Files\PostgreSQL\9.0\bin\psql.exe" -h 192.168.1.12 -p 5432 -d myDB -U my_admin -c "\lo_import 'C://im/zzz4.jpg'";
where
192.168.1.12 is the IP address of the server system
5432 is the Port number
myDB is server database name
my_admin is the username
"\lo_import 'C://im/zzz4.jpg'" is the query that is fired.
After the image has been inserted into the database I need to update a row in a table like this:
UPDATE species
SET speciesimages=17755; -- OID from previous command.. how to get the OID ??
WHERE species='ACCOAA';
So my question is: how do I get the OID returned after the \lo_import in psql?
I tried running \lo_import 'C://im/zzz4.jpg' in Postgres but I get an error:
ERROR: syntax error at or near ""\lo_import 'C://im/zzz4.jpg'""
LINE 1: "\lo_import 'C://im/zzz4.jpg'"
I also tried this:
update species
set speciesimages=\lo_import 'C://im/zzz4.jpg'
where species='ACAAC04';
But I get this error:
ERROR: syntax error at or near "\"
LINE 2: set speciesimages=\lo_import 'C://im/zzz4.jpg'
^

Answer 1

As your file resides on your local machine and you want to import the blob to a remote server, you have two options:
1) Transfer the file to the server and use the server-side function:
UPDATE species
SET speciesimages = lo_import('/path/to/server-local/file/zzz4.jpg')
WHERE species = 'ACAAC04';
2) Use the psql meta-command like you have it.
But you cannot mix psql meta commands with SQL-commands, that's impossible.
Use the psql variable :LASTOID in an UPDATE command that you launch immediately after the \lo_import meta command in the same psql session:
UPDATE species
SET speciesimages = :LASTOID
WHERE species = 'ACAAC04';
To script that (works in Linux, I am not familiar with Windows shell scripting):
echo "\lo_import '/path/to/my/file/zzz4.jpg' \\\\ UPDATE species SET speciesimages = :LASTOID WHERE species = 'ACAAC04';" | \
psql -h 192.168.1.12 -p 5432 -d myDB -U my_admin
\\ is the separator meta-command. You need to double the \, in a "" string, because the shell interprets one layer.
\ before the newline is just the line continuation in Linux shells.
Alternative syntax (tested on Linux again):
psql -h 192.168.1.12 -p 5432 -d myDB -U my_admin << EOF
\lo_import '/path/to/my/file/zzz4.jpg'
UPDATE species
SET speciesimages = :LASTOID
WHERE species = 'ACAAC04';
EOF

Answer 2

After importing an image with this command:
\lo_import '$imagePath' '$imageName'
You can then find the description of the binary by querying the pg_catalog.pg_largeobject_metadata table which stores the oid value you need.
Ie:
"SELECT oid as `"ID`",
pg_catalog.obj_description(oid, 'pg_largeobject') as `"Description`"
FROM pg_catalog.pg_largeobject_metadata WHERE pg_catalog.obj_description(oid,'pg_largeobject') = '$image' limit 1 "

Answer 3

Here's how to do it if your field is type bytea.
\lo_import '/cygdrive/c/Users/Chloe/Downloads/Contract.pdf'
update contracts set contract = lo_get(:LASTOID) where id = 77;
Use \lo_list and \lo_unlink after you import.