org.apache.drill.exec.record

Enum RecordBatch.IterOutcome

java.lang.Object

java.lang.Enum<RecordBatch.IterOutcome>

org.apache.drill.exec.record.RecordBatch.IterOutcome

All Implemented Interfaces:

Serializable, Comparable<RecordBatch.IterOutcome>

Enclosing interface:

RecordBatch

public static enum RecordBatch.IterOutcome
extends Enum<RecordBatch.IterOutcome>

Describes the outcome of incrementing RecordBatch forward by a call to RecordBatch.next().

Key characteristics of the return value sequence:

• OK_NEW_SCHEMA always appears unless STOP appears. (A batch returns OK_NEW_SCHEMA before returning NONE even if the batch has zero rows.)
• OK_NEW_SCHEMA always appears before OK appears.
• The last value is always NONE or STOP, and NONE and STOP appear only as the last value.

Details:

For normal completion, the basic sequence of return values from calls to next() on a RecordBatch is:

1. an OK_NEW_SCHEMA value followed by zero or more OK values,
2. zero or more subsequences each having an OK_NEW_SCHEMA value followed by zero or more OK values, and then
3. a NONE value.

In addition to that basic sequence, NOT_YET and OUT_OF_MEMORY values can appear anywhere in the subsequence before the terminal value (NONE or STOP).

For abnormal termination, the sequence is truncated (before the NONE) and ends with STOP. That is, the sequence begins with a subsequence that is some prefix of a normal-completion sequence and that does not contain NONE, and ends with STOP.

(The normal-completion return sequence is matched by the following regular-expression-style grammar:

     ( ( NOT_YET | OUT_OF_MEMORY )*  OK_NEW_SCHEMA
       ( NOT_YET | OUT_OF_MEMORY )*  OK )*
     )+
     ( NOT_YET | OUT_OF_+MEMORY )*  NONE
   

)

Enum Constant Summary

Enum Constants

Enum Constant and Description
NONE Normal completion of batch.
NOT_YET No data yet.
OK Zero or more records with same schema.
OK_NEW_SCHEMA New schema, maybe with records.
OUT_OF_MEMORY Out of memory (not fatal).
STOP Non-completion (abnormal) termination.

Method Summary

Methods

Modifier and Type	Method and Description
static RecordBatch.IterOutcome	valueOf(String name) Returns the enum constant of this type with the specified name.
static RecordBatch.IterOutcome[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

NONE

public static final RecordBatch.IterOutcome NONE

Normal completion of batch.

The call to RecordBatch.next() read no records, the batch has and will have no more results to return, and next() must not be called again.

This value will be returned only after OK_NEW_SCHEMA has been returned at least once (not necessarily immediately after).

OK

public static final RecordBatch.IterOutcome OK

Zero or more records with same schema.

The call to RecordBatch.next() read zero or more records, the schema has not changed since the last time OK_NEW_SCHEMA was returned, and the batch will have more results to return (at least completion or abnormal termination (NONE or STOP)). (next() should be called again.)

This will be returned only after OK_NEW_SCHEMA has been returned at least once (not necessarily immediately after).

OK_NEW_SCHEMA

public static final RecordBatch.IterOutcome OK_NEW_SCHEMA

New schema, maybe with records.

The call to RecordBatch.next() changed the schema and vector structures and read zero or more records, and the batch will have more results to return (at least completion or abnormal termination (NONE or STOP)). (next() should be called again.)

STOP

public static final RecordBatch.IterOutcome STOP

Non-completion (abnormal) termination.

The call to RecordBatch.next() reports that the query has terminated other than by normal completion, and that the caller must not call any of the schema-access or data-access methods nor call next() again.

The caller can consume its QueryContext to understand the current state of things.

NOT_YET

public static final RecordBatch.IterOutcome NOT_YET

No data yet.

The call to RecordBatch.next() read no data, and the batch will have more results to return in the future (at least completion or abnormal termination (NONE or STOP)). The caller should call next() again, but should do so later (including by returning NOT_YET to its caller).

Normally, the caller should perform any locally available work while waiting for incoming data from the callee, for example, doing partial sorts on already received data while waiting for additional data to sort.

Used by batches that haven't received incoming data yet.

OUT_OF_MEMORY

public static final RecordBatch.IterOutcome OUT_OF_MEMORY

Out of memory (not fatal).

The call to RecordBatch.next(), including upstream operators, was unable to allocate memory and did not read any records, and the batch will have more results to return (at least completion or abnormal termination (NONE or STOP)). The caller should release memory if it can (including by returning OUT_OF_MEMORY to its caller) and call next() again.

Method Detail

values

public static RecordBatch.IterOutcome[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (RecordBatch.IterOutcome c : RecordBatch.IterOutcome.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static RecordBatch.IterOutcome valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null