Cassandra only one row is inserted when expected 100k - python-3.x

Question

I tried to CQL Python driver to insert 100k rows,
# no_of_rows = 100k
for row in range(no_of_rows):
session.execute("INSERT INTO test_table (key1, key2, key3) VALUES ('test', 'test', 'test'"))
but only one row is inserted into test_table (using Cassandra CQL Shell and select * from test_table), how to fix the issue?
UPDATE
If I tried
for row in range(no_of_rows):
session.execute("INSERT INTO test_table (key1, key2, key3) VALUES ('test' + str(row), 'test', 'test'"))
no rows were inserted, here key1 is the primary key.
describe test_table,
CREATE TABLE test_keyspace.test_table (
key1 text PRIMARY KEY,
key2 text,
key3 text
) WITH bloom_filter_fp_chance = 0.01
AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
AND comment = ''
AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
AND crc_check_chance = 1.0
AND dclocal_read_repair_chance = 0.1
AND default_time_to_live = 0
AND gc_grace_seconds = 864000
AND max_index_interval = 2048
AND memtable_flush_period_in_ms = 0
AND min_index_interval = 128
AND read_repair_chance = 0.0
AND speculative_retry = '99PERCENTILE';

Answer 1

Cassandra primary keys are unique. 100000 in-place writes to the same key(s) leaves you with 1 row.
Which means if your primary key structure is PRIMARY KEY(key1,key2,key3) and you INSERT 'test','test','test' 100000 times...
...it'll write 'test','test','test' to the same partition 100000 times.
To get your Python code to work, I made some adjustments, such as creating a separate variable for the key (key1) and using a prepared statement:
pStatement = session.prepare("""
INSERT INTO test_table (key1, key2, key3) VALUES (?, ?, ?);
""")
no_of_rows=100000
for row in range(no_of_rows):
key='test' + str(row)
session.execute(pStatement,[key,'test','test'])
using Cassandra CQL Shell and select * from test_table
I feel compelled to mention, that both multi-key (querying for more than one partition key at a time) and unbound queries (SELECTs without a WHERE clause) are definite anti-patterns in Cassandra. They may appear work fine in a dev/test environment. But when you get to a production-scale cluster with dozens of nodes, these types of queries will introduce a lot of network time into the equation, as they will have to scan each node to compile the query results.

Answer 2

Your new code has a bug in string concatenation. It should be:
for row in range(no_of_rows):
session.execute("INSERT INTO test_table (key1, key2, key3) VALUES ('test" + str(row) + "', 'test', 'test')")