allow_suspicious_* session settings

These settings are available in system.settings and are autogenerated from source.

allow_suspicious_codecs

If it is set to true, allow to specify meaningless compression codecs.

allow_suspicious_fixed_string_types

In CREATE TABLE statement allows creating columns of type FixedString(n) with n > 256. FixedString with length >= 256 is suspicious and most likely indicates a misuse

allow_suspicious_indices

Reject primary/secondary indexes and sorting keys with identical expressions

allow_suspicious_low_cardinality_types

Allows or restricts using LowCardinality with data types with fixed size of 8 bytes or less: numeric data types and FixedString(8_bytes_or_less).

For small fixed values using of LowCardinality is usually inefficient, because ClickHouse stores a numeric index for each row. As a result:

• Disk space usage can rise.
• RAM consumption can be higher, depending on a dictionary size.
• Some functions can work slower due to extra coding/encoding operations.

Merge times in MergeTree-engine tables can grow due to all the reasons described above.

Possible values:

• 1 — Usage of LowCardinality is not restricted.
• 0 — Usage of LowCardinality is restricted.

allow_suspicious_primary_key

Allow suspicious PRIMARY KEY/ORDER BY for MergeTree (i.e. SimpleAggregateFunction).

allow_suspicious_ttl_expressions

Reject TTL expressions that don’t depend on any of table’s columns. It indicates a user error most of the time.

allow_suspicious_types_in_group_by

Allows or restricts using Variant and Dynamic types in GROUP BY keys.

allow_suspicious_types_in_order_by

Allows or restricts using Variant and Dynamic types in ORDER BY keys.

allow_suspicious_variant_types

In CREATE TABLE statement allows specifying Variant type with similar variant types (for example, with different numeric or date types). Enabling this setting may introduce some ambiguity when working with values with similar types.