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81 lines
2.5 KiB
Python
81 lines
2.5 KiB
Python
# fetch.py -- example about declaring cursors
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#
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# Copyright (C) 2001-2010 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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curs = conn.cursor()
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try:
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curs.execute("CREATE TABLE test_fetch (val int4)")
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except:
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conn.rollback()
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curs.execute("DROP TABLE test_fetch")
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curs.execute("CREATE TABLE test_fetch (val int4)")
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conn.commit()
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# we use this function to format the output
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def flatten(l):
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"""Flattens list of tuples l."""
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return map(lambda x: x[0], l)
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# insert 20 rows in the table
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for i in range(20):
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curs.execute("INSERT INTO test_fetch VALUES(%s)", (i,))
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conn.commit()
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# does some nice tricks with the transaction and postgres cursors
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# (remember to always commit or rollback before a DECLARE)
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#
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# we don't need to DECLARE ourselves, psycopg now supports named
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# cursors (but we leave the code here, comments, as an example of
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# what psycopg is doing under the hood)
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#
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#curs.execute("DECLARE crs CURSOR FOR SELECT * FROM test_fetch")
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#curs.execute("FETCH 10 FROM crs")
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#print "First 10 rows:", flatten(curs.fetchall())
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#curs.execute("MOVE -5 FROM crs")
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#print "Moved back cursor by 5 rows (to row 5.)"
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#curs.execute("FETCH 10 FROM crs")
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#print "Another 10 rows:", flatten(curs.fetchall())
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#curs.execute("FETCH 10 FROM crs")
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#print "The remaining rows:", flatten(curs.fetchall())
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ncurs = conn.cursor("crs")
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ncurs.execute("SELECT * FROM test_fetch")
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print("First 10 rows:", flatten(ncurs.fetchmany(10)))
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ncurs.scroll(-5)
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print("Moved back cursor by 5 rows (to row 5.)")
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print("Another 10 rows:", flatten(ncurs.fetchmany(10)))
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print("Another one:", list(ncurs.fetchone()))
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print("The remaining rows:", flatten(ncurs.fetchall()))
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conn.rollback()
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curs.execute("DROP TABLE test_fetch")
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conn.commit()
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