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92 lines
2.7 KiB
Python
92 lines
2.7 KiB
Python
# lobject.py - lobject example
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#
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# Copyright (C) 2001-2006 Federico Di Gregorio <fog@debian.org>
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#
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# psycopg2 is free software: you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published
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# by the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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# License for more details.
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## put in DSN your DSN string
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DSN = 'dbname=test'
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## don't modify anything below this line (except for experimenting)
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import sys
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import psycopg2
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if len(sys.argv) > 1:
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DSN = sys.argv[1]
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print("Opening connection using dsn:", DSN)
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conn = psycopg2.connect(DSN)
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print("Encoding for this connection is", conn.encoding)
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# this will create a large object with a new random oid, we'll
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# use it to make some basic tests about read/write and seek.
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lobj = conn.lobject()
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loid = lobj.oid
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print("Created a new large object with oid", loid)
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print("Manually importing some binary data into the object:")
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data = open("somehackers.jpg").read()
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len = lobj.write(data)
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print(" imported", len, "bytes of data")
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conn.commit()
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print("Trying to (re)open large object with oid", loid)
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lobj = conn.lobject(loid)
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print("Manually exporting the data from the lobject:")
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data1 = lobj.read()
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len = lobj.tell()
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lobj.seek(0, 0)
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data2 = lobj.read()
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if data1 != data2:
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print("ERROR: read after seek returned different data")
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open("somehackers_lobject1.jpg", 'wb').write(data1)
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print(" written", len, "bytes of data to somehackers_lobject1.jpg")
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lobj.unlink()
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print("Large object with oid", loid, "removed")
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conn.commit()
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# now we try to use the import and export functions to do the same
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lobj = conn.lobject(0, 'n', 0, "somehackers.jpg")
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loid = lobj.oid
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print("Imported a new large object with oid", loid)
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conn.commit()
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print("Trying to (re)open large object with oid", loid)
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lobj = conn.lobject(loid, 'n')
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print("Using export() to export the data from the large object:")
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lobj.export("somehackers_lobject2.jpg")
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print(" exported large object to somehackers_lobject2.jpg")
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lobj.unlink()
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print("Large object with oid", loid, "removed")
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conn.commit()
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# this will create a very large object with a new random oid.
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lobj = conn.lobject()
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loid = lobj.oid
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print("Created a new large object with oid", loid)
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print("Manually importing a lot of data into the object:")
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data = "data" * 1000000
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len = lobj.write(data)
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print(" imported", len, "bytes of data")
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conn.rollback()
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print("\nNow try to load the new images, to check it worked!")
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