Introduced a frozenset of string literals that represent SQL NULL values, enhancing the inference and nullability detection processes. Implemented helper functions to identify null strings and unify missing value checks for CHAR/TEXT columns. Updated the _null_sentinel_mask function to replace these sentinel values with None, ensuring consistent handling across various data types during data loading. This change improves robustness in managing missing data scenarios.
Introduced a new mechanism to sample non-null values for determining the appropriate datetime parsing strategy, significantly reducing processing time for large datasets. This change replaces the previous full row-walk method with a more efficient sampling technique, enhancing performance while maintaining robust handling of various date formats. Updated comments for clarity on the new approach.
Introduced a locale-independent month lookup and improved date parsing functions to handle various date formats, including SAS and Oracle styles. The new _parse_flexible_date and _parse_flexible_datetime functions provide robust parsing capabilities, accommodating both date-only and datetime inputs. Updated _try_date_coerce and _try_datetime_coerce to utilize these new functions, ensuring better handling of diverse date formats during data loading.
