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#------------------------------------------------------------------------------

# ReturnLobsAsStrings.py

# Returns all CLOB values as strings and BLOB values as bytes. The

# performance of this technique is significantly better than fetching the LOBs

# and then reading the contents of the LOBs as it avoids round-trips to the

# database. Be aware, however, that this method requires contiguous memory so

# is not usable for very large LOBs.

# This script requires cx_Oracle 5.0 and higher.

#------------------------------------------------------------------------------

import cx_Oracle

import SampleEnv

def OutputTypeHandler(cursor, name, defaultType, size, precision, scale):

if defaultType == cx_Oracle.CLOB:

return cursor.var(cx_Oracle.LONG_STRING, arraysize = cursor.arraysize)

if defaultType == cx_Oracle.BLOB:

return cursor.var(cx_Oracle.LONG_BINARY, arraysize = cursor.arraysize)

connection = cx_Oracle.connect(SampleEnv.GetMainConnectString())

connection.outputtypehandler = OutputTypeHandler

cursor = connection.cursor()

# add some data to the tables

print("Populating tables with data...")

cursor.execute("truncate table TestClobs")

cursor.execute("truncate table TestBlobs")

longString = ""

for i in range(10):

char = chr(ord('A') + i)

longString += char * 25000

# uncomment the line below for cx_Oracle 5.3 and earlier

# cursor.setinputsizes(None, cx_Oracle.LONG_STRING)

cursor.execute("insert into TestClobs values (:1, :2)",

(i + 1, "STRING " + longString))

# uncomment the line below for cx_Oracle 5.3 and earlier

# cursor.setinputsizes(None, cx_Oracle.LONG_BINARY)

cursor.execute("insert into TestBlobs values (:1, :2)",

(i + 1, longString.encode("ascii")))

connection.commit()

# fetch the data and show the results

print("CLOBS returned as strings")

cursor.execute("""

select

IntCol,

ClobCol

from TestClobs

order by IntCol""")

for intCol, value in cursor:

print("Row:", intCol, "string of length", len(value))

print()

print("BLOBS returned as bytes")

cursor.execute("""

select

IntCol,

BlobCol

from TestBlobs

order by IntCol""")

for intCol, value in cursor:

print("Row:", intCol, "string of length", value and len(value) or 0)

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