Authors

Forward Xu, Jark Wu

Status

Current state: "Under Discussion"

Discussion thread: http://apache-flink-mailing-list-archive.1008284.n3.nabble.com/DISCUSS-Support-JSON-functions-in-Flink-SQL-td32674.html

JIRA: here (<- link to https://issues.apache.org/jira/browse/FLINK-XXXX)

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Discussion thread

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JIRA

Jira

server	ASF JIRA
serverId	5aa69414-a9e9-3523-82ec-879b028fb15b
key	FLINK-9477

Release

1.15

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

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Query Functions

Use in SQL:

SQL SYNTAX	DESCRIPTION	RETURN TYPE
JSON_EXISTS(jsonValue, path [ { TRUE \| FALSE \| UNKNOWN \| ERROR } ON ERROR ] )	Whether a jsonValue satisfies a search criterion described using JSON path expression path.	BOOLEAN
JSON_VALUE(jsonValue, path [ RETURNING type ] [ { ERROR \| NULL \| DEFAULT expr } ON EMPTY ] [ { ERROR \| NULL \| DEFAULT expr } ON ERROR ] )	Extract an SQL scalar from a jsonValue using JSON path expression path.	if no "RETURNING type" clause, STRING is returned. If a "RETURNING type" clause is included, an attempt is made to cast to the specified type. For example: json_value ('{"foo": 100}', 'lax $ .foo' returning integer null on empty) will return an integer type.
JSON_QUERY(jsonValue, path [ { WITHOUT [ ARRAY ] \| WITH [ CONDITIONAL \| UNCONDITIONAL ] [ ARRAY ] } WRAPPER ] [ { ERROR \| NULL \| EMPTY ARRAY \| EMPTY OBJECT } ON EMPTY ] [ { ERROR \| NULL \| EMPTY ARRAY \| EMPTY OBJECT } ON ERROR ] )	Extract a JSON object or JSON array from jsonValue using the path JSON path expression.	STRING

Note: The ON ERROR and ON EMPTY clauses define the fallback behavior of the function when an error is thrown or a null value is about to be returned.

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Use in TableApi:

jsonExists

JAVA/PYTHON/SCALA	DESCRIPTION	RETURN TYPE
STRING.jsonExists((Expression path [,JsonExistsBehavior behavior])	Whether a jsonValue satisfies a search criterion described using JSON path expression path. The JsonExistsBehavior is built as follows: behavior = JsonExistsBehavior.TrueOnError ("abc").	BOOLEAN

jsonValue

JAVA/PYTHON/SCALA

DESCRIPTION

RETURN TYPE

STRING.jsonValue(Expression path[,JsonValueBehavior behavior])

Extract an SQL scalar from a jsonValue using JSON path expression path.

The JsonValueBehavior is built as follows:

behavior = JsonValueBehavior.defaultOnEmpty ("abc"). NullOnError(). or

behavior = JsonValueBehavior.returnInt().defaultOnEmpty ("abc"). NullOnError().

if no "RETURNING type" clause, STRING is returned. If a "RETURNING type" clause is included, an attempt is made to cast to the specified type. For example: json_value ('{"foo": 100}', 'lax $ .foo' returning integer null on empty) will return an integer type.

jsonQuery

JAVA/PYTHON/SCALA

DESCRIPTION

RETURN TYPE

STRING.jsonQuery(Expression path [,JsonQueryBehavior behavior])

Extract a JSON object or JSON array from jsonValue using the path JSON path expression.

The JsonQueryBehavior is built as follows:

behavior = JsonQueryBehavior.withoutArray().defaultOnEmpty ("abc"). NullOnError ().

STRING

Example Data:

{"a": "[1,2]", "b": [1,2], "c": "hi"}

Comparison:

OPERATOR	$.A	$.B	$.C
JSON_EXISTS	true	true	true
JSON_VALUE	[1, 2]	error	hi
JSON QUERY WITHOUT ARRAY WRAPPER	error	[1, 2]	error
JSON QUERY WITH UNCONDITIONAL ARRAY WRAPPER	[ “[1,2]” ]	[ [1,2] ]	[ “hi” ]
JSON QUERY WITH CONDITIONAL ARRAY WRAPPER	[ “[1,2]” ]	[1,2]	[ “hi” ]

Constructor Functions

Use in SQL:

SQL SYNTAX	DESCRIPTION	RETURN TYPE
JSON_OBJECT( { [ KEY ] name VALUE value [ FORMAT JSON ] \| name : value [ FORMAT JSON ] } * [ { NULL \| ABSENT } ON NULL ] )	Construct JSON object using a series of key (name) value (value) pairs.	STRING
JSON_OBJECTAGG( { [ KEY ] name VALUE value [ FORMAT JSON ] \| name : value [ FORMAT JSON ] } [ { NULL \| ABSENT } ON NULL ] )	Aggregate function to construct a JSON object using a key (name) value (value) pair.	STRING
JSON_ARRAY( { value [ FORMAT JSON ] } * [ { NULL \| ABSENT } ON NULL ] )	Construct a JSON array using a series of values (value).	STRING
JSON_ARRAYAGG( value [ FORMAT JSON ] [ ORDER BY orderItem [, orderItem ]* ] [ { NULL \| ABSENT } ON NULL ] )	Aggregate function to construct a JSON array using a value (value).	STRING

Use in TableApi:

jsonObject

JAVA/PYTHON/SCALA

DESCRIPTION

RETURN TYPE

jsonObject(ANY1, ANY2, …[,SqlJsonConstructorNullClause.NULL_ON_NULL])

Construct JSON object using a series of key (name) value (value) pairs.Table API currently only supports JSON string operations.

This means NULL ON NULL.

STRING

jsonObject(ANY1, ANY2, …[,SqlJsonConstructorNullClause.ABSENT_ON_NULL])

This means ABSENT ON NULL.

STRING

jsonObjectAgg

JAVA/PYTHON/SCALA	DESCRIPTION	RETURN TYPE
jsonObjectAgg(ANY1,ANY2[,SqlJsonConstructorNullClause.NULL_ON_NULL])	Aggregate function to construct a JSON object using a key (name) value (value) pair.This means NULL ON NULL.	STRING
jsonObjectAgg(ANY1,ANY2[,SqlJsonConstructorNullClause.ABSENT_ON_NULL])	This means ABSENT ON NULL.	STRING

jsonArray

JAVA/PYTHON/SCALA	DESCRIPTION	RETURN TYPE
jsonArray(ANY1, ANY2, ...[,SqlJsonConstructorNullClause.NULL_ON_NULL])	Construct a JSON array using a series of values (value). This means NULL ON NULL.	STRING
jsonArray(ANY1, ANY2, ...[,SqlJsonConstructorNullClause.ABSENT_ON_NULL])	This means ABSENT ON NULL.	STRING

jsonArrayAgg

JAVA/PYTHON/SCALA	DESCRIPTION	RETURN TYPE
jsonArrayAgg(ANY[,SqlJsonConstructorNullClause.NULL_ON_NULL])	Aggregate function to construct a JSON array using a value (value). This means NULL ON NULL.	STRING
jsonArrayAgg(ANY[,SqlJsonConstructorNullClause.ABSENT_ON_NULL])	This means ABSENT ON NULL.	STRING

Note: The flag FORMAT JSON indicates the value is formatted as JSON character string. When FORMAT JSON is used, the value should be de-parse from JSON character string to a SQL structured value.

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If ORDER BY clause is provided, JSON_ARRAYAGG sorts the input rows into the specified order before performing aggregation.

Comparison:

OPERATOR	RESULT
JSON_OBJECT('id', 87, 'name', 'carrot')	{"id": 87, "name": "carrot"}
JSON_ARRAY(1, "abc", NULL, TRUE)	[1, "abc", null, true]

Simple Data Table T1:

o_id	attribute	value
2	color	red
2	fabric	silk
3	color	green
3	shape	square

SELECT o_id, JSON_OBJECTAGG(attribute, value) FROM t1 GROUP BY o_id;

OPERATOR	o_id	AFTER AGG
JSON_OBJECTAGG(attribute, value)	2	{"color": "red", "fabric": "silk"}
JSON_OBJECTAGG(attribute, value)	3	{"color": "green", "shape": "square"}

SELECT o_id, JSON_ARRAYAGG(attribute) AS attributes FROM t1 GROUP BY o_id;

OPERATOR	o_id	AFTER AGG
JSON_ARRAYAGG(attribute)	2	["color", "fabric"]
JSON_ARRAYAGG(attribute)	3	["color", "shape"]

Comparison Operators

Applications will frequently want to ensure that the data they expect to consume as JSON data is, indeed, JSON data. The IS JSON predicate determines whether the value of a specified string does or does not conform to the structural rules for JSON. The syntax of the IS JSON predicate is:

Use in SQL:

SQL SYNTAX	DESCRIPTION	RETURN TYPE
jsonValue IS JSON [ VALUE ]	Whether jsonValue is a JSON value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS NOT JSON [ VALUE ]	Whether jsonValue is not a JSON value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS JSON SCALAR	Whether jsonValue is a JSON scalar value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS NOT JSON SCALAR	Whether jsonValue is not a JSON scalar value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS JSON OBJECT	Whether jsonValue is a JSON object.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS NOT JSON OBJECT	Whether jsonValue is not a JSON object.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS JSON ARRAY	Whether jsonValue is a JSON array.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
jsonValue IS NOT JSON ARRAY	Whether jsonValue is not a JSON array.Table API functions currently only support JSON strings as input parameters.	BOOLEAN

Use in TableApi:

JAVA/PYTHON/SCALA	DESCRIPTION	RETURN TYPE
ANY.isJsonValue()	Whether jsonValue is a JSON value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isNotJsonValue()	Whether jsonValue is not a JSON value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isJsonScalar()	Whether jsonValue is a JSON scalar value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isNotJsonScalar()	Whether jsonValue is not a JSON scalar value.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isJsonObject()	Whether jsonValue is a JSON object.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isNotJsonObject()	Whether jsonValue is not a JSON object.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isJsonArray()	Whether jsonValue is a JSON array.Table API functions currently only support JSON strings as input parameters.	BOOLEAN
ANY.isNotJsonArray()	Whether jsonValue is not a JSON array.Table API functions currently only support JSON strings as input parameters.	BOOLEAN

The test example:

tester.checkBoolean("'{}' is json value", true);

tester.checkBoolean("'{]' is json value", false);

tester.checkBoolean("'{}' is json object", true);

tester.checkBoolean("'[]' is json object", false);

tester.checkBoolean("'{}' is json array", false);

tester.checkBoolean("'[]' is json array", true);

tester.checkBoolean("'100' is json scalar", true);

tester.checkBoolean("'[]' is json scalar", false);

tester.checkBoolean("'{}' is not json value", false);

tester.checkBoolean("'{]' is not json value", true);

tester.checkBoolean("'{}' is not json object", false);

tester.checkBoolean("'[]' is not json object", true);

tester.checkBoolean("'{}' is not json array", true);

tester.checkBoolean("'[]' is not json array", false);

tester.checkBoolean("'100' is not json scalar", false);

tester.checkBoolean("'[]' is not json scalar", true);

Implementation Details

Table Api interface proposal

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Query Functions

Constructor Functions

Comparison Operators

Implementation Details

Table Api interface proposal

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Old Version 9

New Version Current

Key

Status

Query Functions

Constructor Functions

Comparison Operators

Implementation Details

Table Api interface proposal