SQL/JSON query functions

This introduces the SQL/JSON functions for querying JSON data using
jsonpath expressions. The functions are:

JSON_EXISTS()
JSON_QUERY()
JSON_VALUE()

All of these functions only operate on jsonb. The workaround for now is
to cast the argument to jsonb.

JSON_EXISTS() tests if the jsonpath expression applied to the jsonb
value yields any values. JSON_VALUE() must return a single value, and an
error occurs if it tries to return multiple values. JSON_QUERY() must
return a json object or array, and there are various WRAPPER options for
handling scalar or multi-value results. Both these functions have
options for handling EMPTY and ERROR conditions.

Nikita Glukhov

Reviewers have included (in no particular order) Andres Freund, Alexander
Korotkov, Pavel Stehule, Andrew Alsup, Erik Rijkers, Zihong Yu,
Himanshu Upadhyaya, Daniel Gustafsson, Justin Pryzby.

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru

1 files changed, 59 insertions, 0 deletions

diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6bf212b01a1..0ff4ba08846 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1595,6 +1595,23 @@ typedef struct TriggerTransition
 /* Nodes for SQL/JSON support */
 
 /*
+ * JsonQuotes -
+ *		representation of [KEEP|OMIT] QUOTES clause for JSON_QUERY()
+ */
+typedef enum JsonQuotes
+{
+	JS_QUOTES_UNSPEC,			/* unspecified */
+	JS_QUOTES_KEEP,				/* KEEP QUOTES */
+	JS_QUOTES_OMIT				/* OMIT QUOTES */
+} JsonQuotes;
+
+/*
+ * JsonPathSpec -
+ *		representation of JSON path constant
+ */
+typedef char *JsonPathSpec;
+
+/*
  * JsonOutput -
  *		representation of JSON output clause (RETURNING type [FORMAT format])
  */
@@ -1606,6 +1623,48 @@ typedef struct JsonOutput
 } JsonOutput;
 
 /*
+ * JsonArgument -
+ *		representation of argument from JSON PASSING clause
+ */
+typedef struct JsonArgument
+{
+	NodeTag		type;
+	JsonValueExpr *val;			/* argument value expression */
+	char	   *name;			/* argument name */
+} JsonArgument;
+
+/*
+ * JsonCommon -
+ *		representation of common syntax of functions using JSON path
+ */
+typedef struct JsonCommon
+{
+	NodeTag		type;
+	JsonValueExpr *expr;		/* context item expression */
+	Node	   *pathspec;		/* JSON path specification expression */
+	char	   *pathname;		/* path name, if any */
+	List	   *passing;		/* list of PASSING clause arguments, if any */
+	int			location;		/* token location, or -1 if unknown */
+} JsonCommon;
+
+/*
+ * JsonFuncExpr -
+ *		untransformed representation of JSON function expressions
+ */
+typedef struct JsonFuncExpr
+{
+	NodeTag		type;
+	JsonExprOp	op;				/* expression type */
+	JsonCommon *common;			/* common syntax */
+	JsonOutput *output;			/* output clause, if specified */
+	JsonBehavior *on_empty;		/* ON EMPTY behavior, if specified */
+	JsonBehavior *on_error;		/* ON ERROR behavior, if specified */
+	JsonWrapper	wrapper;		/* array wrapper behavior (JSON_QUERY only) */
+	bool		omit_quotes;	/* omit or keep quotes? (JSON_QUERY only) */
+	int			location;		/* token location, or -1 if unknown */
+} JsonFuncExpr;
+
+/*
  * JsonKeyValue -
  *		untransformed representation of JSON object key-value pair for
  *		JSON_OBJECT() and JSON_OBJECTAGG()