Revert SQL/JSON features

The reverts the following and makes some associated cleanups:

    commit f79b803dc: Common SQL/JSON clauses
    commit f4fb45d15: SQL/JSON constructors
    commit 5f0adec25: Make STRING an unreserved_keyword.
    commit 33a377608: IS JSON predicate
    commit 1a36bc9db: SQL/JSON query functions
    commit 606948b05: SQL JSON functions
    commit 49082c2cc: RETURNING clause for JSON() and JSON_SCALAR()
    commit 4e34747c8: JSON_TABLE
    commit fadb48b00: PLAN clauses for JSON_TABLE
    commit 2ef6f11b0: Reduce running time of jsonb_sqljson test
    commit 14d3f24fa: Further improve jsonb_sqljson parallel test
    commit a6baa4bad: Documentation for SQL/JSON features
    commit b46bcf7a4: Improve readability of SQL/JSON documentation.
    commit 112fdb352: Fix finalization for json_objectagg and friends
    commit fcdb35c32: Fix transformJsonBehavior
    commit 4cd8717af: Improve a couple of sql/json error messages
    commit f7a605f63: Small cleanups in SQL/JSON code
    commit 9c3d25e17: Fix JSON_OBJECTAGG uniquefying bug
    commit a79153b7a: Claim SQL standard compliance for SQL/JSON features
    commit a1e7616d6: Rework SQL/JSON documentation
    commit 8d9f9634e: Fix errors in copyfuncs/equalfuncs support for JSON node types.
    commit 3c633f32b: Only allow returning string types or bytea from json_serialize
    commit 67b26703b: expression eval: Fix EEOP_JSON_CONSTRUCTOR and EEOP_JSONEXPR size.

The release notes are also adjusted.

Backpatch to release 15.

Discussion: https://postgr.es/m/40d2c882-bcac-19a9-754d-4299e1d87ac7@postgresql.org

src/include/utils/formatting.h

@@ -17,9 +17,6 @@
 #ifndef _FORMATTING_H_
 #define _FORMATTING_H_
 
-#define DCH_DATED	0x01
-#define DCH_TIMED	0x02
-#define DCH_ZONED	0x04
 
 extern char *str_tolower(const char *buff, size_t nbytes, Oid collid);
 extern char *str_toupper(const char *buff, size_t nbytes, Oid collid);
@@ -32,6 +29,5 @@ extern char *asc_initcap(const char *buff, size_t nbytes);
 extern Datum parse_datetime(text *date_txt, text *fmt, Oid collid, bool strict,
 							Oid *typid, int32 *typmod, int *tz,
 							bool *have_error);
-extern int	datetime_format_flags(const char *fmt_str, bool *have_error);
 
 #endif

src/include/utils/json.h

@@ -16,35 +16,9 @@
 
 #include "lib/stringinfo.h"
 
-typedef enum					/* type categories for datum_to_json */
-{
-	JSONTYPE_NULL,				/* null, so we didn't bother to identify */
-	JSONTYPE_BOOL,				/* boolean (built-in types only) */
-	JSONTYPE_NUMERIC,			/* numeric (ditto) */
-	JSONTYPE_DATE,				/* we use special formatting for datetimes */
-	JSONTYPE_TIMESTAMP,
-	JSONTYPE_TIMESTAMPTZ,
-	JSONTYPE_JSON,				/* JSON itself (and JSONB) */
-	JSONTYPE_ARRAY,				/* array */
-	JSONTYPE_COMPOSITE,			/* composite */
-	JSONTYPE_CAST,				/* something with an explicit cast to JSON */
-	JSONTYPE_OTHER				/* all else */
-} JsonTypeCategory;
-
 /* functions in json.c */
 extern void escape_json(StringInfo buf, const char *str);
 extern char *JsonEncodeDateTime(char *buf, Datum value, Oid typid,
 								const int *tzp);
-extern bool to_json_is_immutable(Oid typoid);
-extern void json_categorize_type(Oid typoid, JsonTypeCategory *tcategory,
-								 Oid *outfuncoid);
-extern Datum to_json_worker(Datum val, JsonTypeCategory tcategory,
-							Oid outfuncoid);
-extern Datum json_build_object_worker(int nargs, Datum *args, bool *nulls,
-									  Oid *types, bool absent_on_null,
-									  bool unique_keys);
-extern Datum json_build_array_worker(int nargs, Datum *args, bool *nulls,
-									 Oid *types, bool absent_on_null);
-extern bool json_validate(text *json, bool check_unique_keys, bool throw_error);
 
 #endif							/* JSON_H */

src/include/utils/jsonb.h

@@ -329,8 +329,6 @@ typedef struct JsonbParseState
 	JsonbValue	contVal;
 	Size		size;
 	struct JsonbParseState *next;
-	bool		unique_keys;	/* Check object key uniqueness */
-	bool		skip_nulls;		/* Skip null object fields */
 } JsonbParseState;
 
 /*
@@ -376,22 +374,6 @@ typedef struct JsonbIterator
 	struct JsonbIterator *parent;
 } JsonbIterator;
 
-/* unlike with json categories, we need to treat json and jsonb differently */
-typedef enum					/* type categories for datum_to_jsonb */
-{
-	JSONBTYPE_NULL,				/* null, so we didn't bother to identify */
-	JSONBTYPE_BOOL,				/* boolean (built-in types only) */
-	JSONBTYPE_NUMERIC,			/* numeric (ditto) */
-	JSONBTYPE_DATE,				/* we use special formatting for datetimes */
-	JSONBTYPE_TIMESTAMP,		/* we use special formatting for timestamp */
-	JSONBTYPE_TIMESTAMPTZ,		/* ... and timestamptz */
-	JSONBTYPE_JSON,				/* JSON */
-	JSONBTYPE_JSONB,			/* JSONB */
-	JSONBTYPE_ARRAY,			/* array */
-	JSONBTYPE_COMPOSITE,		/* composite */
-	JSONBTYPE_JSONCAST,			/* something with an explicit cast to JSON */
-	JSONBTYPE_OTHER				/* all else */
-} JsonbTypeCategory;
 
 /* Support functions */
 extern uint32 getJsonbOffset(const JsonbContainer *jc, int index);
@@ -419,14 +401,10 @@ extern void JsonbHashScalarValueExtended(const JsonbValue *scalarVal,
 										 uint64 *hash, uint64 seed);
 
 /* jsonb.c support functions */
-extern Datum jsonb_from_text(text *js, bool unique_keys);
 extern char *JsonbToCString(StringInfo out, JsonbContainer *in,
 							int estimated_len);
 extern char *JsonbToCStringIndent(StringInfo out, JsonbContainer *in,
 								  int estimated_len);
-extern Jsonb *JsonbMakeEmptyArray(void);
-extern Jsonb *JsonbMakeEmptyObject(void);
-extern char *JsonbUnquote(Jsonb *jb);
 extern bool JsonbExtractScalar(JsonbContainer *jbc, JsonbValue *res);
 extern const char *JsonbTypeName(JsonbValue *jb);
 
@@ -434,15 +412,4 @@ extern Datum jsonb_set_element(Jsonb *jb, Datum *path, int path_len,
 							   JsonbValue *newval);
 extern Datum jsonb_get_element(Jsonb *jb, Datum *path, int npath,
 							   bool *isnull, bool as_text);
-extern bool to_jsonb_is_immutable(Oid typoid);
-extern void jsonb_categorize_type(Oid typoid, JsonbTypeCategory *tcategory,
-								  Oid *outfuncoid);
-extern Datum to_jsonb_worker(Datum val, JsonbTypeCategory tcategory,
-							 Oid outfuncoid);
-extern Datum jsonb_build_object_worker(int nargs, Datum *args, bool *nulls,
-									   Oid *types, bool absent_on_null,
-									   bool unique_keys);
-extern Datum jsonb_build_array_worker(int nargs, Datum *args, bool *nulls,
-									  Oid *types, bool absent_on_null);
-
 #endif							/* __JSONB_H__ */

src/include/utils/jsonfuncs.h

@@ -45,9 +45,6 @@ extern void pg_parse_json_or_ereport(JsonLexContext *lex, JsonSemAction *sem);
 /* report an error during json lexing or parsing */
 extern void json_ereport_error(JsonParseErrorType error, JsonLexContext *lex);
 
-/* get first JSON token */
-extern JsonTokenType json_get_first_token(text *json, bool throw_error);
-
 extern uint32 parse_jsonb_index_flags(Jsonb *jb);
 extern void iterate_jsonb_values(Jsonb *jb, uint32 flags, void *state,
 								 JsonIterateStringValuesAction action);
@@ -58,8 +55,4 @@ extern Jsonb *transform_jsonb_string_values(Jsonb *jsonb, void *action_state,
 extern text *transform_json_string_values(text *json, void *action_state,
 										  JsonTransformStringValuesAction transform_action);
 
-extern Datum json_populate_type(Datum json_val, Oid json_type,
-								Oid typid, int32 typmod,
-								void **cache, MemoryContext mcxt, bool *isnull);
-
 #endif

src/include/utils/jsonpath.h

@@ -15,11 +15,8 @@
 #define JSONPATH_H
 
 #include "fmgr.h"
-#include "executor/tablefunc.h"
 #include "nodes/pg_list.h"
-#include "nodes/primnodes.h"
 #include "utils/jsonb.h"
-#include "utils/jsonfuncs.h"
 
 typedef struct
 {
@@ -177,7 +174,6 @@ extern bool jspGetBool(JsonPathItem *v);
 extern char *jspGetString(JsonPathItem *v, int32 *len);
 extern bool jspGetArraySubscript(JsonPathItem *v, JsonPathItem *from,
 								 JsonPathItem *to, int i);
-extern bool jspIsMutable(JsonPath *path, List *varnames, List *varexprs);
 
 extern const char *jspOperationName(JsonPathItemType type);
 
@@ -252,37 +248,4 @@ extern JsonPathParseResult *parsejsonpath(const char *str, int len);
 
 extern int	jspConvertRegexFlags(uint32 xflags);
 
-/*
- * Evaluation of jsonpath
- */
-
-/* External variable passed into jsonpath. */
-typedef struct JsonPathVariableEvalContext
-{
-	char	   *name;
-	Oid			typid;
-	int32		typmod;
-	struct ExprContext *econtext;
-	struct ExprState *estate;
-	MemoryContext mcxt;			/* memory context for cached value */
-	Datum		value;
-	bool		isnull;
-	bool		evaluated;
-} JsonPathVariableEvalContext;
-
-/* SQL/JSON item */
-extern void JsonItemFromDatum(Datum val, Oid typid, int32 typmod,
-							  JsonbValue *res);
-
-extern bool JsonPathExists(Datum jb, JsonPath *path, List *vars, bool *error);
-extern Datum JsonPathQuery(Datum jb, JsonPath *jp, JsonWrapper wrapper,
-						   bool *empty, bool *error, List *vars);
-extern JsonbValue *JsonPathValue(Datum jb, JsonPath *jp, bool *empty,
-								 bool *error, List *vars);
-
-extern int	EvalJsonPathVar(void *vars, char *varName, int varNameLen,
-							JsonbValue *val, JsonbValue *baseObject);
-
-extern PGDLLIMPORT const TableFuncRoutine JsonbTableRoutine;
-
 #endif