Class MutableTupleSchema.ColumnHandle

java.lang.Object
org.apache.drill.exec.physical.impl.scan.v3.schema.MutableTupleSchema.ColumnHandle
Enclosing class:
MutableTupleSchema

public static class MutableTupleSchema.ColumnHandle extends Object
Holder for a column to allow inserting and replacing columns within the top-level project list. Changes to the column within the holder must go through the tuple itself so we can track schema versions.

Tracks the resolution status of each individual column as described for ScanSchemaTracker. Models a column throughout the projection lifecycle. Columns evolve from unresolved to resolved at different times. Columns are either implicit (defined by the framework) or normal (defined by the reader). Columns can be defined by the planner (via a defined schema), partially defined (via a provided schema), or discovered by the reader. Regardless of the path to definition, by the time the first batch is delivered downstream, each column has an output schema which describes the data.

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