While deserialize csv input, if we set the config input_format_csv_empty_as_default = true, which would set default value to field if the input is empty, and this is also take effect for Nullable(String) type, in this case, if the input is a empty string, then the field will be set default value as NULL, as show below
Here it is not suitable，to set NULL when the input is empty for Nullable(String) type, and it is better to set a empty string for the field.
Documentation entry for user-facing changes
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Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):
Fix problems as described in https://github.com/ClickHouse/ClickHouse/pull/58225
While deserialize csv input, if we set the config
input_format_csv_empty_as_default = true, which would set default value to field if the input is empty, and this is also take effect for Nullable(String) type, in this case, if the input is a empty string, then the field will be set default value asNULL, as show belowHere it is not suitable，to set
NULLwhen the input is empty forNullable(String)type, and it is better to set a empty string for the field.Documentation entry for user-facing changes