On 5/9/2013 12:08 PM, Nelson Green wrote: > Thanks Karl, but I'm trying to do this from a psql shell. I can't use > the C functions there, can I? > > > On Thu, May 9, 2013 at 11:21 AM, Karl Denninger <k...@denninger.net > <mailto:k...@denninger.net>> wrote: > > On 5/9/2013 11:12 AM, Karl Denninger wrote: >> On 5/9/2013 10:51 AM, Achilleas Mantzios wrote: >>> >>> Take a look here first : >>> >>> http://www.postgresql.org/docs/9.2/interactive/datatype-binary.html >>> >>> >>> >>> then here : >>> >>> http://www.dbforums.com/postgresql/1666200-insert-jpeg-files-into-bytea-column.html >>> >>> >>> >>> didnt try it myself tho. >>> >>> >>> >>> Most of the time people manipulate bytea's using a higher level >>> programming lang. >>> >>> >>> >>> >>> >>> On Πεμ 09 Μαΐ 2013 10:34:35 Nelson Green wrote: >>> >>> On Thu, May 9, 2013 at 10:20 AM, Achilleas Mantzios >>> <ach...@matrix.gatewaynet.com >>> <mailto:ach...@matrix.gatewaynet.com>> wrote: >>> >>> why not bytea? >>> >>> >>> Hi Achilleas, >>> >>> Actually I was asking if bytea is the correct datatype, and if >>> so, would someone mind providing a simple example of how to >>> insert and retrieve the image through the psql client. >>> >>> Let's say I have an employee named Paul Kendell, who's employee >>> ID is 880918. Their badge number will be PK00880918, and their >>> badge photo is named /tmp/PK00880918.jpg. What would the INSERT >>> statement look like to put that information into the >>> security_badge table, and what would the SELECT statement look >>> like to retrieve that record? >>> >>> Thanks for your time. >>> >>> >>> >>> much more control, much more information, IMHO. >>> >>> In our DB evolving from an initial 7.1 back in 2001, and >>> currently on 9.0, >>> >>> we have been storing everything binary in bytea's. >>> >>> >>> >>> There are downsides in both solutions, you just have to have >>> good reasons >>> >>> to not use bytea. >>> >>> >>> >>> On Πεμ 09 Μαΐ 2013 10:04:18 Nelson Green wrote: >>> >>> Good morning list, >>> >>> I am designing a system that will have a table for security >>> badges, and we want to store the ID badge photo. These are small >>> files, averaging about 500K in size. We have made the decision >>> to store the image as a BLOB in the table itself for a variety >>> of reasons. However, I am having trouble understanding just how >>> to do that. >>> >>> The table structures: >>> >>> CREATE TABLE employee >>> ( >>> employee_id INTEGER NOT NULL, >>> employee_lastname VARCHAR(35) NOT NULL, >>> employee_firstname VARCHAR(35) NOT NULL, >>> employee_mi CHAR(1), >>> PRIMARY KEY (employee_id) >>> ); >>> >>> CREATE TABLE security_badge >>> ( >>> badge_number CHAR(10) NOT NULL, >>> employee_id INTEGER NOT NULL >>> REFERENCES employee(employee_id), >>> badge_photo ????, >>> PRIMARY KEY (badge_number) >>> ); >>> >>> What datatype should I use for the badge_photo (bytea?), and >>> what are the commands to insert the picture accessing the server >>> remotely through psql, and to retrieve the photos as well, please? >>> >>> Thanks, >>> Nelson >>> >>> >>> >>> - >>> >>> Achilleas Mantzios >>> >>> IT DEV >>> >>> IT DEPT >>> >>> Dynacom Tankers Mgmt >>> >>> >>> >>> >>> - >>> >>> Achilleas Mantzios >>> >>> IT DEV >>> >>> IT DEPT >>> >>> Dynacom Tankers Mgmt >>> >> >> To encode: >> >> >> write_conn = Postgresql communication channel in your software >> that is open to write to the table >> >> char *out; >> size_t out_length, badge_length; >> >> badge_length = function-to-get-length-of(badge_binary_data); /* >> You have to know how long it is */ >> >> out = PQescapeByteaConn(write_conn, badge_binary_data, >> badge_length, &out_length); /* Convert */ >> >> That function allocates the required memory for the conversion. >> You now have an encoded string you can "insert" or "update" >> with. Once you use it in an "insert" or "update" function you >> then must "PQfreemem(out)" to release the memory that was allocated. >> >> To recover the data you do: >> >> PQresult *result; >> >> result = PQexec(write_conn, "select badge_photo blah-blah-blah"); >> .... >> out = PQunescapeBytea(PQgetvalue(result, 0, 0)); /* Get the >> returned piece of the tuple and convert it */ >> >> "out" now contains the BINARY (decoded) photo data. When done >> with it you: >> >> PQfreemem(out) to release the memory that was allocated. >> >> That's the rough outline -- see here: >> >> http://www.postgresql.org/docs/current/static/libpq-exec.html >> >> -- >> Karl Denninger >> k...@denninger.net <mailto:k...@denninger.net> >> /Cuda Systems LLC/ > Oops -- forgot the second parameter on the "PQunescapebytea" call :-) > > Yeah, that would be bad: > > size_t out_length; > > out = PQunescapeBytea(PQgetvalue(result, 0, 0), &out_length); /* > Get the returned piece of the tuple and convert it */ > > Otherwise, being binary data, how would you know how long it is? :-) > > BTW I use these functions extensively in my forum code and have > stored anything from avatars (small image files) to multi-megabyte > images. Works fine. You have to figure out what the type of image > is, of course (or know that in advance) and tag it somehow if you > intend to do something like display it on a web page as the > correct mime type content header has to be sent down when the > image is requested. What I do in my application is determine the > image type at storage time (along with width and height and a few > other things) and save it into the table along with the data. > > > -- > Karl Denninger > k...@denninger.net <mailto:k...@denninger.net> > /Cuda Systems LLC/ > > Someone else already got that, but -- no :-)
-- Karl Denninger k...@denninger.net /Cuda Systems LLC/
