![]() ![]() The data files backing a Delta table are never deleted automatically data files are deleted only when you run VACUUM. To time travel to a previous version, you must retain both the log and the data files for that version. If a partition column is defined by one of the preceding expressions, and a query filters data using the underlying base column of a generation expression, Delta Lake looks at the relationship between the base column and the generated column, and populates partition filters based on the generated partition column if possible. SUBSTRING(col, pos, len) and the type of col is STRINGĭATE_FORMAT(col, format) and the type of col is TIMESTAMP. ![]() Three partition columns defined by YEAR(col), MONTH(col), DAY(col) and the type of col is TIMESTAMP.įour partition columns defined by YEAR(col), MONTH(col), DAY(col), HOUR(col) and the type of col is TIMESTAMP. Two partition columns defined by YEAR(col), MONTH(col) and the type of col is TIMESTAMP. YEAR(col) and the type of col is TIMESTAMP. The following restrictions apply to generated columns:Ī generation expression can use any SQL functions in Spark that always return the same result when given the same argument values, except the following types of functions:įor Delta Lake 1.1.0 and above, MERGE operations support generated columns when you set .autoMerge.enabled to true.ĭelta Lake may be able to generate partition filters for a query whenever a partition column is defined by one of the following expressions:ĬAST(col AS DATE) and the type of col is TIMESTAMP. Generated columns are stored as if they were normal columns. generatedAlwaysAs ( "CAST(dateOfBirth AS DATE)" ). addColumn ( "lastName", "STRING", comment = "surname" ). property ( "description", "table with people data" ). execute () // Create or replace table with path and add properties DeltaTable. Create table in the metastore DeltaTable. Access Delta tables from external data processing engines.Query an older snapshot of a table (time travel). ![]()
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