```sql
CREATE TABLE test_tbl
(   `ip` String, `ipv6` IPv6 MATERIALIZED toIPv6(ip) )
ENGINE = Memory;

insert into test_tbl(ip) values ( 'fe80::9801:43ff:fe1f:7690'), ('1.1.1.1'), (''), ('::ffff:1.1.1.1' );

 DB::Exception: Invalid IPv6 value: while executing 'FUNCTION _CAST(toIPv6(ip) :: 2, 'IPv6' :: 1)


set cast_ipv4_ipv6_default_on_conversion_error=1;
insert into test_tbl(ip) values ( 'fe80::9801:43ff:fe1f:7690'), ('1.1.1.1'), (''), ('::ffff:1.1.1.1' );
 
 DB::Exception: Invalid IPv6 value: while executing 'FUNCTION _CAST(toIPv6(ip)
```

`toIPv6OrDefault` does not help in this case.

```sql
CREATE TABLE test_tbl
(   `ip` String, `ipv6` IPv6 MATERIALIZED toIPv6OrDefault(ip) )
ENGINE = Memory;

insert into test_tbl(ip) values ( 'fe80::9801:43ff:fe1f:7690'), ('1.1.1.1'), (''), ('::ffff:1.1.1.1' );
  DB::Exception: Invalid IPv6 value: while executing 'FUNCTION _CAST(toIPv6OrD

insert into test_tbl(ip) values ( 'fe80::9801:43ff:fe1f:7690'), ('1.1.1.1'), (''), ('::ffff:1.1.1.1' ), ('garbudge');
  DB::Exception: Invalid IPv6 value: while executing 'FUNCTION
```

WA:

```sql
CREATE TABLE test_tbl
(   `ip` String, `ipv6` IPv6 MATERIALIZED if(ip='', '::', ip) )
ENGINE = Memory;

insert into test_tbl(ip) values ( 'fe80::9801:43ff:fe1f:7690'), ('1.1.1.1'), (''), ('::ffff:1.1.1.1' );

select ip, ipv6 from test_tbl;
┌─ip────────────────────────┬─ipv6──────────────────────┐
│ fe80::9801:43ff:fe1f:7690 │ fe80::9801:43ff:fe1f:7690 │
│ 1.1.1.1                   │ ::ffff:1.1.1.1            │
│                           │ ::                        │
│ ::ffff:1.1.1.1            │ ::ffff:1.1.1.1            │
└───────────────────────────┴───────────────────────────┘
```
M(Milliseconds, connect_timeout_with_failover_ms, 50, "Connection timeout for selecting first healthy replica.", 0) \
    M(Milliseconds, connect_timeout_with_failover_secure_ms, 100, "Connection timeout for selecting first healthy replica (for secure connections).", 0) \
    M(Seconds, receive_timeout, DBMS_DEFAULT_RECEIVE_TIMEOUT_SEC, "", 0) \
    M(Seconds, send_timeout, DBMS_DEFAULT_SEND_TIMEOUT_SEC, "", 0) \
    M(Seconds, drain_timeout, 3, "Timeout for draining remote connections, -1 means synchronous drain w/o ignoring errors", 0) \
    M(Seconds, tcp_keep_alive_timeout, 290 /* less than DBMS_DEFAULT_RECEIVE_TIMEOUT_SEC */, "The time in seconds the connection needs to remain idle before TCP starts sending keepalive probes", 0) \
    M(Milliseconds, hedged_connection_timeout_ms, 100, "Connection timeout for establishing connection with replica for Hedged requests", 0) \
    M(Milliseconds, receive_data_timeout_ms, 2000, "Connection timeout for receiving first packet of data or packet with positive progress from replica", 0) \
    M(Bool, use_hedged_requests, true, "Use hedged requests for distributed queries", 0) \
    M(Bool, allow_changing_replica_until_first_data_packet, false, "Allow HedgedConnections to change replica until receiving first data packet", 0) \
    M(Milliseconds, queue_max_wait_ms, 0, "The wait time in the request queue, if the number of concurrent requests exceeds the maximum.", 0) \
    M(Milliseconds, connection_pool_max_wait_ms, 0, "The wait time when the connection pool is full.", 0) \
    M(Milliseconds, replace_running_query_max_wait_ms, 5000, "The wait time for running query with the same query_id to finish when setting 'replace_running_query' is active.", 0) \
    M(Milliseconds, kafka_max_wait_ms, 5000, "The wait time for reading from Kafka before retry.", 0) \
    M(Milliseconds, rabbitmq_max_wait_ms, 5000, "The wait time for reading from RabbitMQ before retry.", 0) \
    M(UInt64, poll_interval, DBMS_DEFAULT_POLL_INTERVAL, "Block at the query wait loop on the server for the specified number of seconds.", 0) \
    M(UInt64, idle_connection_timeout, 3600, "Close idle TCP connections after specified number of seconds.", 0) \
    M(UInt64, distributed_connections_pool_size, 1024, "Maximum number of connections with one remote server in the pool.", 0) \
    M(UInt64, connections_with_failover_max_tries, DBMS_CONNECTION_POOL_WITH_FAILOVER_DEFAULT_MAX_TRIES, "The maximum number of attempts to connect to replicas.", 0) \
    M(UInt64, s3_min_upload_part_size, 16*1024*1024, "The minimum size of part to upload during multipart upload to S3.", 0) \
    M(UInt64, s3_upload_part_size_multiply_factor, 2, "Multiply s3_min_upload_part_size by this factor each time s3_multiply_parts_count_threshold parts were uploaded from a single write to S3.", 0) \
    M(UInt64, s3_upload_part_size_multiply_parts_count_threshold, 1000, "Each time this number of parts was uploaded to S3 s3_min_upload_part_size multiplied by s3_upload_part_size_multiply_factor.", 0) \
    M(UInt64, s3_max_single_part_upload_size, 32*1024*1024, "The maximum size of object to upload using singlepart upload to S3.", 0) \
    M(UInt64, s3_max_single_read_retries, 4, "The maximum number of retries during single S3 read.", 0) \
    M(UInt64, s3_max_redirects, 10, "Max number of S3 redirects hops allowed.", 0) \
    M(UInt64, s3_max_connections, 1024, "The maximum number of connections per server.", 0) \
    M(Bool, s3_truncate_on_insert, false, "Enables or disables truncate before insert in s3 engine tables.", 0) \
    M(Bool, s3_create_new_file_on_insert, false, "Enables or disables creating a new file on each insert in s3 engine tables", 0) \
    M(UInt64, hdfs_replication, 0, "The actual number of replications can be specified when the hdfs file is created.", 0) \
    M(Bool, hdfs_truncate_on_insert, false, "Enables or disables truncate before insert in s3 engine tables", 0) \