org.apache.drill.exec.store.easy.json.loader

Class FieldDefn

java.lang.Object

org.apache.drill.exec.store.easy.json.loader.FieldDefn

public class FieldDefn
extends Object

Describes a new field within an object. Allows the listener to control how to handle the field: as unprojected, parsed as a typed field, as text, as JSON, or as a custom parser.

Constructor Summary

Constructors

Constructor and Description
FieldDefn(TupleParser tupleParser, String key, TokenIterator tokenizer)
FieldDefn(TupleParser tupleParser, String key, TokenIterator tokenizer, boolean isArray)

Method Summary

Modifier and Type	Method and Description
ObjectWriter	fieldWriterFor(ColumnMetadata colSchema)
String	key() Returns the field name.
ValueDef	lookahead() Looks ahead to guess the field type based on JSON tokens.
TypeProtos.DataMode	mode(boolean isArray)
JsonStructureParser	parser() Returns the parent parser which is needed to construct standard parsers.
ColumnMetadata	providedColumn()
ScalarWriter	scalarWriterFor(ColumnMetadata colSchema)
ScalarWriter	scalarWriterFor(TypeProtos.MinorType type, boolean isArray)
ColumnMetadata	schemaFor(TypeProtos.MinorType type, boolean isArray)
TokenIterator	tokenizer() Token stream which allows a custom parser to look ahead as needed.
TupleParser	tupleParser()
TupleWriter	writer()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FieldDefn

public FieldDefn(TupleParser tupleParser,
                 String key,
                 TokenIterator tokenizer)

FieldDefn

public FieldDefn(TupleParser tupleParser,
                 String key,
                 TokenIterator tokenizer,
                 boolean isArray)

Method Detail

key

public String key()

Returns the field name.

tupleParser

public TupleParser tupleParser()

tokenizer

public TokenIterator tokenizer()

Token stream which allows a custom parser to look ahead as needed. The caller must "unget" all tokens to leave the tokenizer at the present location. Note that the underlying Jackson parser will return text for the last token consumed, even if tokens are unwound using the token iterator, so do not look ahead past the first field name or value; on look ahead over "static" tokens such as object and array start characters.

parser

public JsonStructureParser parser()

Returns the parent parser which is needed to construct standard parsers.

lookahead

public ValueDef lookahead()

Looks ahead to guess the field type based on JSON tokens. While this is helpful, it really only works if the JSON is structured like a list of tuples, if the initial value is not null, and if initial arrays are not empty. The structure parser cannot see into the future beyond the first field value; the value listener for each field must handle "type-deferral" if needed to handle missing or null values. That is, type-consistency is a semantic task handled by the listener, not a syntax task handled by the parser.

writer

public TupleWriter writer()

providedColumn

public ColumnMetadata providedColumn()

schemaFor

public ColumnMetadata schemaFor(TypeProtos.MinorType type,
                                boolean isArray)

mode

public TypeProtos.DataMode mode(boolean isArray)

scalarWriterFor

public ScalarWriter scalarWriterFor(TypeProtos.MinorType type,
                                    boolean isArray)

scalarWriterFor

public ScalarWriter scalarWriterFor(ColumnMetadata colSchema)

fieldWriterFor

public ObjectWriter fieldWriterFor(ColumnMetadata colSchema)