def query_item(tablename):
t = ti.table_exists(tablename)
if t == None:
print("** Table", tablename, "does not exist in this region")
return
tab = ddb.Table(tablename)
queryResponse = tab.query(KeyConditionExpression=Key('kcol').eq('keyval1'))
# Invalid - OR in key - only one condition allowed in key
# KeyConditionExpression = Key('kcol').eq('keyval1') | Key('kcol').eq('keyval3')
# Invalid - 'query key condition not supported'
# KeyConditionExpression = Key('kcol').begins_with('keyval')
print(queryResponse)
print()
print(len(queryResponse['Items']), "filtered item(s) found",
queryResponse['ScannedCount'], "item(s) were scanned")
count = 0
for item in queryResponse['Items']:
print("Item", count)
for k, v in item.items():
print("-", k, ":", v)
count += 1
return
def scan_items(tablename):
t = ti.table_exists(tablename)
if t == None:
print("** Table", tablename, "does not exist in this region")
return
response = ddb_client.scan(TableName=tablename)
print(len(response['Items']), "item(s) found")
count = 0
for item in response['Items']:
print("Item", count)
for k, v in item.items():
print("-", k, ":", v)
count += 1
# Do a count scan operation
countResponse = ddb_client.scan(TableName=tablename, Select="COUNT")
print()
print("Count:", countResponse['Count'], "Scanned count:",
countResponse['ScannedCount'])
# Do a filtered query - using DDB low-levelclient means using FilterExpression as a string
# Not clear how to format these - get syntax errors.
#filter = "nkeyint = '2'"
#filteredResponse = ddb_client.scan(
# TableName = tablename,
# FilterExpression = filter
#)
# So use the DDB resource-level interface instead, which has a higher-level filtering approach, using Attr objects (see imports)
tab = ddb.Table(tablename)
filteredResponse = tab.scan(
FilterExpression=Attr('nkeyint').eq(2)
& Attr('nkeystring').begins_with('non') # NB & not and
)
print(len(filteredResponse['Items']), "filtered item(s) found",
filteredResponse['ScannedCount'], "item(s) were scanned")
count = 0
for item in filteredResponse['Items']:
print("Item", count)
for k, v in item.items():
print("-", k, ":", v)
count += 1
return
def put_items(tablename):
t = ti.table_exists(tablename)
if t == None:
print("** Table", tablename, "does not exist in this region")
return
count = 0
for d in [("keyval1", 1, "nonkeyval1"), ("keyval2", 2, "nonkeyval2"),
("keyval3", 3, "nonkeyval3")]:
keyval = d[0]
nonkeyintval = d[1]
nonkeystringval = d[2]
# Add records, specifying the key column and two non-key columns
# NB for Python, type seems to be inferred, so just do
# 'colname' : <stringvalue>
# rather than the syntax inplied in the documentation.
# 'colname' : { "S" : <stringvalue> }
print("Adding record", keyval, "...")
itemsDict = {
'kcol': keyval,
'nkeyint': nonkeyintval,
'nkeystring': nonkeystringval
}
# Add another non-key field to one item, don't have to have same fields in each item
if count == 2:
itemsDict['anothernonkey'] = 'abc'
try:
response = ddb_client.put_item(
TableName=tablename,
Item=itemsDict,
ConditionExpression=
'attribute_not_exists(kcol)' # i.e. don't replace existing item with the same key
)
print(response)
except ddb_client.exceptions.ConditionalCheckFailedException as e:
print("- duplicate key, not added")
except Exception as e:
print("Exception", e)
count += 1
return
def delete_items(tablename):
t = ti.table_exists(tablename)
if t == None:
print("** Table", tablename, "does not exist in this region")
return
count = 0
for keyval in ["keyval1", "keyval2", "keyval3"]:
# Add records, specifying the key column and two non-key columns
print("Deleting record", keyval, "...")
keysDict = {'kcol': keyval}
response = ddb_client.delete_item(TableName=tablename, Key=keysDict)
count += 1
print(response)
return
def get_item(tablename) :
t = ti.table_exists(tablename)
if t == None :
print("** Table", tablename, "does not exist in this region")
return
tab = ddb.Table(tablename)
keyval = 'keyval1'
response = tab.get_item(
Key= { 'kcol' : keyval }
)
if 'Item' in response :
print(keyval, "found in table", tablename)
for k,v in response['Item'].items() :
print("-", k, ":", v)
else :
print(keyval, "not found in table", tablename)
return
def update_item(tablename) :
t = ti.table_exists(tablename)
if t == None :
print("** Table", tablename, "does not exist in this region")
return
tab = ddb.Table(tablename)
keyval = 'keyval1'
response = tab.get_item(
Key= { 'kcol' : keyval }
)
nkeyValue = 0
if 'Item' in response :
print(keyval, "found in table", tablename)
for k,v in response['Item'].items() :
print("-", k, ":", v)
nkeyValue = response['Item']['nkeyint']
else :
print(keyval, "not found in table", tablename)
return
nkeyValue2 = nkeyValue + 10
print()
print("Updating nkeyint value from", nkeyValue, "to", nkeyValue2)
updateResponse = tab.update_item(
Key= { 'kcol' : keyval },
UpdateExpression = "SET nkeyint = :val1",
ExpressionAttributeValues = { ':val1' : nkeyValue2 }
)
print(updateResponse)
return