```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(UInt64, limit, 0, "Limit on read rows from the most 'end' result for select query, default 0 means no limit length", 0) \
    M(UInt64, offset, 0, "Offset on read rows from the most 'end' result for select query", 0) \
    \
    M(UInt64, function_range_max_elements_in_block, 500000000, "Maximum number of values generated by function 'range' per block of data (sum of array sizes for every row in a block, see also 'max_block_size' and 'min_insert_block_size_rows'). It is a safety threshold.", 0) \
    M(ShortCircuitFunctionEvaluation, short_circuit_function_evaluation, ShortCircuitFunctionEvaluation::ENABLE, "Setting for short-circuit function evaluation configuration. Possible values: 'enable' - use short-circuit function evaluation for functions that are suitable for it, 'disable' - disable short-circuit function evaluation, 'force_enable' - use short-circuit function evaluation for all functions.", 0) \
    \
    M(String, local_filesystem_read_method, "pread", "Method of reading data from local filesystem, one of: read, pread, mmap, pread_threadpool.", 0) \
    M(String, remote_filesystem_read_method, "threadpool", "Method of reading data from remote filesystem, one of: read, threadpool.", 0) \
    M(Bool, local_filesystem_read_prefetch, false, "Should use prefetching when reading data from local filesystem.", 0) \
    M(Bool, remote_filesystem_read_prefetch, true, "Should use prefetching when reading data from remote filesystem.", 0) \
    M(Int64, read_priority, 0, "Priority to read data from local filesystem. Only supported for 'pread_threadpool' method.", 0) \
    M(UInt64, merge_tree_min_rows_for_concurrent_read_for_remote_filesystem, (20 * 8192), "If at least as many lines are read from one file, the reading can be parallelized, when reading from remote filesystem.", 0) \
    M(UInt64, merge_tree_min_bytes_for_concurrent_read_for_remote_filesystem, (24 * 10 * 1024 * 1024), "If at least as many bytes are read from one file, the reading can be parallelized, when reading from remote filesystem.", 0) \
    M(UInt64, remote_read_min_bytes_for_seek, 4 * DBMS_DEFAULT_BUFFER_SIZE, "Min bytes required for remote read (url, s3) to do seek, instead for read with ignore.", 0) \
    \
    M(UInt64, async_insert_threads, 16, "Maximum number of threads to actually parse and insert data in background. Zero means asynchronous mode is disabled", 0) \
    M(Bool, async_insert, false, "If true, data from INSERT query is stored in queue and later flushed to table in background. Makes sense only for inserts via HTTP protocol. If wait_for_async_insert is false, INSERT query is processed almost instantly, otherwise client will wait until data will be flushed to table", 0) \
    M(Bool, wait_for_async_insert, true, "If true wait for processing of asynchronous insertion", 0) \
    M(Seconds, wait_for_async_insert_timeout, DBMS_DEFAULT_LOCK_ACQUIRE_TIMEOUT_SEC, "Timeout for waiting for processing asynchronous insertion", 0) \
    M(UInt64, async_insert_max_data_size, 100000, "Maximum size in bytes of unparsed data collected per query before being inserted", 0) \
    M(Milliseconds, async_insert_busy_timeout_ms, 200, "Maximum time to wait before dumping collected data per query since the first data appeared", 0) \
    M(Milliseconds, async_insert_stale_timeout_ms, 0, "Maximum time to wait before dumping collected data per query since the last data appeared. Zero means no timeout at all", 0) \
    \
    M(UInt64, remote_fs_read_max_backoff_ms, 10000, "Max wait time when trying to read data for remote disk", 0) \
    M(UInt64, remote_fs_read_backoff_max_tries, 5, "Max attempts to read with backoff", 0) \
    M(Bool, remote_fs_enable_cache, true, "Use cache for remote filesystem. This setting does not turn on/off cache for disks (must me done via disk config), but allows to bypass cache for some queries if intended", 0) \
    M(UInt64, remote_fs_cache_max_wait_sec, 5, "Allow to wait at most this number of seconds for download of current remote_fs_buffer_size bytes, and skip cache if exceeded", 0) \
    \
    M(UInt64, http_max_tries, 10, "Max attempts to read via http.", 0) \
    M(UInt64, http_retry_initial_backoff_ms, 100, "Min milliseconds for backoff, when retrying read via http", 0) \