json_path.h File Reference

This file contains interface support for the JSON path abstraction. More...

#include <assert.h>
#include <stddef.h>
#include <algorithm>
#include <new>
#include <string>
#include <string_view>
#include <utility>
#include "my_alloc.h"
#include "mysql/psi/psi_memory.h"
#include "prealloced_array.h"

Go to the source code of this file.

Classes
class	Json_array_index
	A class that represents the index of an element in a JSON array. More...
class	Json_path_leg
	One path leg in a JSON path expression. More...
struct	Json_path_leg::Array_range
	A structure that represents an array range. More...
class	Json_seekable_path
	A path expression which can be used to seek to a position inside a JSON value. More...
class	Json_path
	A JSON path expression. More...
class	Json_path_clone
	A lightweight path expression. More...

Typedefs
using	Json_path_leg_pointers = Prealloced_array< const Json_path_leg *, 8 >
using	Json_path_iterator = Json_path_leg_pointers::const_iterator

Enumerations
enum	enum_json_path_leg_type {   jpl_member , jpl_array_cell , jpl_array_range , jpl_member_wildcard ,   jpl_array_cell_wildcard , jpl_ellipsis }
	The type of a Json_path_leg. More...

Functions
bool	parse_path (size_t path_length, const char *path_expression, Json_path *path, size_t *bad_index)
	Initialize a Json_path from a path expression. More...
bool	parse_path (const String &path_value, bool forbid_wildcards, Json_path *json_path)
	A helper function that uses the above one as workhorse. More...
bool	clone_without_autowrapping (const Json_path *source_path, Json_path_clone *target_path, Json_wrapper *doc, PSI_memory_key key)
	Clone a source path to a target path, stripping out legs which are made redundant by the auto-wrapping rule from the WL#7909 spec and further extended in the WL#9831 spec: More...

Detailed Description

This file contains interface support for the JSON path abstraction.

The path abstraction is described by the functional spec attached to WL#7909.

Typedef Documentation

Json_path_iterator

using Json_path_iterator = Json_path_leg_pointers::const_iterator

Json_path_leg_pointers

using Json_path_leg_pointers = Prealloced_array<const Json_path_leg *, 8>

Enumeration Type Documentation

enum_json_path_leg_type

enum enum_json_path_leg_type

The type of a Json_path_leg.

Enumerator
jpl_member	A path leg that represents a JSON object member (such as .name). This path leg matches a single member in a JSON object.
jpl_array_cell	A path leg that represents a JSON array cell (such as [10]). This path leg matches a single element in a JSON object.
jpl_array_range	A path leg that represents a range in a JSON array (such as [2 to 7]).
jpl_member_wildcard	A path leg that represents the member wildcard. A path leg that represents the member wildcard (.*), which matches all the members of a JSON object.
jpl_array_cell_wildcard	A path leg that represents the array wildcard ([*]), which matches all the elements of a JSON array.
jpl_ellipsis	A path leg that represents the ellipsis (**), which matches any JSON value and recursively all the JSON values nested within it if it is an object or an array.

Function Documentation

clone_without_autowrapping()

bool clone_without_autowrapping	(	const Json_path *	source_path,
		Json_path_clone *	target_path,
		Json_wrapper *	doc,
		PSI_memory_key	key
	)

Clone a source path to a target path, stripping out legs which are made redundant by the auto-wrapping rule from the WL#7909 spec and further extended in the WL#9831 spec:

"If an array cell path leg or an array range path leg is evaluated against a non-array value, the result of the evaluation is the same as if the non-array value had been wrapped in a single-element array."

See also

Json_path_leg::is_autowrap

Parameters

[in]	source_path	The original path.
[in,out]	target_path	The clone to be filled in.
[in]	doc	The document to seek through.
[in]	key	Instrumented memory key

Returns

True if an error occurred. False otherwise.

parse_path() [1/2]

bool parse_path	(	const String &	path_value,
		bool	forbid_wildcards,
		Json_path *	json_path
	)

A helper function that uses the above one as workhorse.

Entry point for for JSON_TABLE (Table_function_json class) and Json_path_cache. Raises an error if the path expression is syntactically incorrect. Raises an error if the path expression contains wildcard tokens but is not supposed to. Otherwise updates the supplied Json_path object with the parsed path.

Parameters

[in]	path_value	A String to be interpreted as a path.
[in]	forbid_wildcards	True if the path shouldn't contain * or **
[out]	json_path	The object that will hold the parsed path

Returns

false on success (valid path or NULL), true on error

parse_path() [2/2]

bool parse_path	(	size_t	path_length,
		const char *	path_expression,
		Json_path *	path,
		size_t *	bad_index
	)

Initialize a Json_path from a path expression.

Stops parsing on the first error. It initializes the Json_path and returns false if the path is parsed successfully. Otherwise, it returns false. In that case, the output bad_index argument will contain an index into the path expression. The parsing failed near that index.

Parameters

[in]	path_length	The length of the path expression.
[in]	path_expression	The string form of the path expression.
[out]	path	The Json_path object to be initialized.
[out]	bad_index	If null is returned, the parsing failed around here.

Returns

false on success, true on error

Initialize a Json_path from a path expression.