Default to varchar(max) for inferred string columns#385
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The previous `varchar(8000)` default in TYPE_LABELS, string_type() and string_size() silently truncated any inferred-width string column at 8000 characters. Fabric Warehouse supports varchar(max); use that as the default when no explicit size is provided. string_size() now returns -1 as the sentinel for max, mirroring how T-SQL represents varchar(max) in sys.columns. string_type() and can_expand_to() were updated to handle the sentinel.
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Fixes #384.
FabricColumndefaultedSTRING/VARCHAR/NVARCHARtoVARCHAR(8000)inTYPE_LABELS, and bothstring_type()andstring_size()fell back to8000when no explicit size was supplied. Any inferred-width string column was silently hard-capped at 8000 characters — long-text source columns (JSON payloads, free-text fields, serialized blobs) lost the tail beyond byte 8000 with no warning or error.Fabric Warehouse supports
varchar(max), so this PR makes that the default when no size is provided.Changes
TYPE_LABELS:STRING,VARCHAR, andNVARCHARnow map toVARCHAR(MAX).string_type(size): returnsvarchar(max)whensizeisNoneor non-positive; otherwisevarchar({size}).string_size(): returns-1(the T-SQL sentinel forvarchar(max)) whenchar_sizeisNone, instead of8000.can_expand_to(): treats-1as the widest possible size so comparisons stay correct.Users who want a fixed-width column can still declare it explicitly via a contract or by setting
char_sizedirectly.Testing
The maintainers can wire this through the project's test suite. Happy to extend the change with adapter unit tests covering the new sentinel paths if that's the preferred follow-up.