PostgreSQL 10.0 preview 功能增强 - SQL:2016标准(之SQL/JSON) Oracle 12c兼容

4 minute read


PostgreSQL 很多年前,就支持JSON类型,属于最早支持JSON类型的关系数据库。内置了两个JSON类型json与jsonb。



Oracle 12c支持的JSON与该标准非常接近(不知道是不是Oracle想用标准来后来居上呢?)


PostgreSQL json, jsonb已有的生态,包括自身的用法,周边的例如pljava, pljavascript, plv8等存储过程引擎。感兴趣可以谷歌百科。



Hi there,  
Attached patch is an implementation of SQL/JSON data model from SQL-2016  
standard (ISO/IEC 9075-2:2016(E)), which was published 2016-12-15 and is  
available only for purchase from ISO web site ( Unfortunately I didn't find any  
public sources of the standard or any preview documents, but Oracle  
implementation of json support in 12c release 2 is very close (,  
also we used  to understand some details.  
Postgres has already two json data types - json and jsonb and implementing  
another json data type, which strictly conforms the standard, would be not  
a good idea. Moreover, SQL standard doesn’t describe data type, but only  
data model, which “comprises SQL/JSON items and SQL/JSON sequences. The  
components of the SQL/JSON data model are:  
1) An SQL/JSON item is defined recursively as any of the following:  
a) An SQL/JSON scalar, defined as a non-null value of any of the following  
predefined (SQL) types:  
character string with character set Unicode, numeric, Boolean, or datetime.  
b) An SQL/JSON null, defined as a value that is distinct from any value of  
any SQL type.  
NOTE 122 — An SQL/JSON null is distinct from the SQL null value.  
c) An SQL/JSON array, defined as an ordered list of zero or more SQL/JSON  
items, called the SQL/JSON  
elements of the SQL/JSON array.  
d) An SQL/JSON object, defined as an unordered collection of zero or more  
SQL/JSON members….  
Our jsonb corresponds to SQL/JSON with UNIQUE KEYS and implicit ordering of  
keys and our main intention was to provide support of jsonb as a most  
important and usable data type.  
We created repository for reviewing (ask for write access) -  
Examples of usage can be found in src/test/regress/sql/sql_json.sql  
The whole documentation about json support should be reorganized and added,  
and we plan to do this before release. We need help of community here.  
Our goal is to provide support of main features of SQL/JSON to release 10,  
as we discussed at developers meeting in Brussels (Andrew Dunstan has  
kindly agreed to review the patch).  
We had not much time to develop the complete support, because of standard  
availability), but hope all major features are here, namely, all nine  
functions as described in the standard (but see implementation notes below):  
“All manipulation (e.g., retrieval, creation, testing) of SQL/JSON items is  
performed through a number of SQL/JSON functions. There are nine such  
functions, categorized as SQL/JSON retrieval functions and SQL/JSON  
construction functions. The SQL/JSON retrieval functions are characterized  
by operating on JSON data and returning an SQL value (possibly a Boolean  
value) or a JSON value. The SQL/JSON construction functions return JSON  
data created from operations on SQL data or other JSON data.  
The SQL/JSON retrieval functions are:  
— <JSON value function>: extracts an SQL value of a predefined type from a  
JSON text.  
— <JSON query>: extracts a JSON text from a JSON text.  
— <JSON table>: converts a JSON text to an SQL table.  
— <JSON predicate>: tests whether a string value is or is not properly  
formed JSON text.  
— <JSON exists predicate>: tests whether an SQL/JSON path expression  
returns any SQL/JSON items.  
The SQL/JSON construction functions are:  
— <JSON object constructor>: generates a string that is a serialization of  
an SQL/JSON object.  
— <JSON array constructor>: generates a string that is a serialization of  
an SQL/JSON array.  
— <JSON object aggregate constructor>: generates, from an aggregation of  
SQL data, a string that is a serialization  
of an SQL/JSON object.  
— <JSON array aggregate constructor>: generates, from an aggregation of SQL  
data, a string that is a serialization  
of an SQL/JSON array.  
A JSON-returning function is an SQL/JSON construction function or  
The standard describes SQL/JSON path language, which used by SQL/JSON query  
operators to query JSON. It defines path language as string literal. We  
implemented the path language as  JSONPATH data type, since other  
approaches are not friendly to planner and executor.  
The functions and JSONPATH provide a new functionality for json support,  
namely, ability to operate (in standard specified way) with json structure  
at SQL-language level - the often requested feature by the users.  
The patch is consists of about 15000 insertions (about 5000 lines are from  
tests), passes all regression tests and doesn’t touches critical parts, so  
we hope with community help to bring it to committable state.  
Authors: Nikita Glukhov, Teodor Sigaev, Oleg Bartunov and Alexander Korotkov  
Implementation notes:  
   We didn’t implemented ‘datetime’ support, since it’s not clear from  
   JSON_OBJECT/JSON_OBJECTAGG (KEY <key> VALUE <value>, ...) doesn’t  
   implemented, only (<key>:<value>, …) and (<key> VALUE <value>, …) are  
   supported, because of  grammar conflicts with leading KEY keyword.  
   FORMAT (JSON|JSONB))  in JSON_ARRAYAGG with subquery  doesn’t supported,  
   because of grammar conflicts with non-reserved word FORMAT.  
   JSONPATH implemented only for  jsonb data type , so JSON_EXISTS(),  
   JSON_VALUE(), JSON_QUERY() and JSON_TABLE() doesn’t works if context item  
   is of json data type.  
   Some methods and predicates for JSONPATH not yet implemented, for  
   example  .type(), .size(), .keyvalue(),  predicates  like_regex, starts  
   with, etc. They are not key features and we plan to make them in next  
   JSONPATH doesn’t support expression for index array, like [2+3 to  
   $upperbound], only simple constants like [5, 7 to 12] are supported.  
   JSONPATH extensions to standard: .** (wildcard path accessor), .key  
   (member accessor without leading @).  
   FORMAT JSONB extension to standard for returning jsonb - standard  
   specifies possibility of returning custom type.  
   JSON_EXISTS(), JSON_VALUE(), JSON_QUERY() are implemented using new  
   executor node JsonExpr.  
   JSON_TABLE() is transformed into joined subselects with JSON_VALUE() and  
   JSON_QUERY() in target list.  
   JSON_OBJECT(), JSON_ARRAY() constructors and IS JSON predicate are  
   transformed into raw function calls.  
   Added explicit casts bytea=>jsonb and jsonb=>bytea (for jsonb=>bytea  
   output using RETURNING bytea FORMAT JSONB and corresponding bytea=>jsonb  
   input using <jsonb_bytea_expr> FORMAT JSONB).  
Best regards,  





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