SQL Server backup files → Parquet

Datatypes conversion mapping when exporting a table from a SQL Server full backup (.bak) using the ArpeMSBackup ADBC driver (--connectiontype backup_mssql) to Parquet format.

Platform availability

backup_mssql is available on Windows x64 and Linux x64 only. It is not supported on Linux ARM64.

Compared with adbc_mssql

The mapping is the one of adbc_mssql, with the same values, except for two of its defaults:

• time(7), datetime2(7), datetimeoffset(7): backup_mssql keeps the 100 ns resolution (nanosecond unit); adbc_mssql writes microseconds by default.
• geography, geometry: backup_mssql writes the SQL Server binary serialization (as adbc_mssql with adbc.arpemssql.geospatial=varbinary); adbc_mssql converts them to WKB with GeoParquet metadata by default.

Source	SQL Server backup file (backup_mssql)
Format	Parquet
FastBCP	1.5.0.0
Test Status	OK (31/31 Nullable)

Parquet Schema: testdatatypes_nullable

name	physical_type	converted_type	logical_type
col_bigint	INT64	—	—
col_int	INT32	—	—
col_smallint	INT32	INT_16	IntType(bitWidth=16, isSigned=1)
col_tinyint	INT32	UINT_8	IntType(bitWidth=8, isSigned=0)
col_bit	BOOLEAN	—	—
col_decimal	FIXED_LEN_BYTE_ARRAY	DECIMAL	DecimalType(scale=2, precision=18)
col_numeric	FIXED_LEN_BYTE_ARRAY	DECIMAL	DecimalType(scale=2, precision=18)
col_money	FIXED_LEN_BYTE_ARRAY	DECIMAL	DecimalType(scale=4, precision=19)
col_smallmoney	FIXED_LEN_BYTE_ARRAY	DECIMAL	DecimalType(scale=4, precision=10)
col_float	DOUBLE	—	—
col_real	FLOAT	—	—
col_date	INT32	DATE	DateType()
col_time	INT64	—	TimeType(isAdjustedToUTC=0, unit=NANOS)
col_datetime	INT64	TIMESTAMP_MILLIS	TimestampType(isAdjustedToUTC=0, unit=MILLIS)
col_datetime2	INT64	—	TimestampType(isAdjustedToUTC=0, unit=NANOS)
col_datetimeoffset	INT64	—	TimestampType(isAdjustedToUTC=1, unit=NANOS)
col_smalldatetime	INT64	TIMESTAMP_MILLIS	TimestampType(isAdjustedToUTC=0, unit=MILLIS)
col_char	BYTE_ARRAY	UTF8	StringType()
col_varchar	BYTE_ARRAY	UTF8	StringType()
col_nchar	BYTE_ARRAY	UTF8	StringType()
col_nvarchar	BYTE_ARRAY	UTF8	StringType()
col_text	BYTE_ARRAY	UTF8	StringType()
col_ntext	BYTE_ARRAY	UTF8	StringType()
col_binary	BYTE_ARRAY	—	—
col_varbinary	BYTE_ARRAY	—	—
col_image	BYTE_ARRAY	—	—
col_uniqueidentifier	BYTE_ARRAY	UTF8	StringType()
col_xml	BYTE_ARRAY	UTF8	StringType()
col_geography	BYTE_ARRAY	—	—
col_geometry	BYTE_ARRAY	—	—
col_sql_variant	BYTE_ARRAY	UTF8	StringType()

Notes

• datetimeoffset is exported as a UTC instant (isAdjustedToUTC=1); the original offset is not kept.
• time and datetime2 keep their 7 decimal digits (nanosecond unit, the last two digits always zero).
• uniqueidentifier is written in lowercase (b85ed2b1-24f5-4b71-8d1a-6d1e4e3f0c11), like adbc_mssql.
• Strings are converted to UTF-8 from the column's collation code page (char, varchar, text) or from UTF-16 (nchar, nvarchar, ntext); UTF-8 collations (SQL Server 2019+) are read as they are.
• xml is decoded from the binary XML stored in the backup to text.
• geography, geometry and hierarchyid (CLR types) are exported as their binary serialization.
• sql_variant is exported as text (CAST(value AS nvarchar); ISO 8601 for dates, 0x… for binary values).