Add SQL/JSON query functions

This introduces the following SQL/JSON functions for querying JSON
data using jsonpath expressions:

JSON_EXISTS(), which can be used to apply a jsonpath expression to a
JSON value to check if it yields any values.

JSON_QUERY(), which can be used to to apply a jsonpath expression to
a JSON value to get a JSON object, an array, or a string.  There are
various options to control whether multi-value result uses array
wrappers and whether the singleton scalar strings are quoted or not.

JSON_VALUE(), which can be used to apply a jsonpath expression to a
JSON value to return a single scalar value, producing an error if it
multiple values are matched.

Both JSON_VALUE() and JSON_QUERY() functions have options for
handling EMPTY and ERROR conditions, which can be used to specify
the behavior when no values are matched and when an error occurs
during jsonpath evaluation, respectively.

Author: Nikita Glukhov <n.gluhov@postgrespro.ru>
Author: Teodor Sigaev <teodor@sigaev.ru>
Author: Oleg Bartunov <obartunov@gmail.com>
Author: Alexander Korotkov <aekorotkov@gmail.com>
Author: Andrew Dunstan <andrew@dunslane.net>
Author: Amit Langote <amitlangote09@gmail.com>
Author: Peter Eisentraut <peter@eisentraut.org>
Author: Jian He <jian.universality@gmail.com>

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, Álvaro Herrera, Jian He, Anton A. Melnikov,
Nikita Malakhov, Peter Eisentraut, Tomas Vondra

Discussion: https://postgr.es/m/cd0bb935-0158-78a7-08b5-904886deac4b@postgrespro.ru
Discussion: https://postgr.es/m/20220616233130.rparivafipt6doj3@alap3.anarazel.de
Discussion: https://postgr.es/m/abd9b83b-aa66-f230-3d6d-734817f0995d%40postgresql.org
Discussion: https://postgr.es/m/CA+HiwqHROpf9e644D8BRqYvaAPmgBZVup-xKMDPk-nd4EpgzHw@mail.gmail.com
Discussion: https://postgr.es/m/CA+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com

4 files changed, 33 insertions, 0 deletions

diff --git a/src/include/utils/formatting.h b/src/include/utils/formatting.h
index 7ea1a70f712..cde030414ee 100644
--- a/src/include/utils/formatting.h
+++ b/src/include/utils/formatting.h
@@ -29,5 +29,6 @@ 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,
 							struct Node *escontext);
+extern bool datetime_format_has_tz(const char *fmt_str);
 
 #endif
diff --git a/src/include/utils/jsonb.h b/src/include/utils/jsonb.h
index e38dfd4901f..d589ace5a21 100644
--- a/src/include/utils/jsonb.h
+++ b/src/include/utils/jsonb.h
@@ -422,6 +422,7 @@ extern char *JsonbToCString(StringInfo out, JsonbContainer *in,
 							int estimated_len);
 extern char *JsonbToCStringIndent(StringInfo out, JsonbContainer *in,
 								  int estimated_len);
+extern char *JsonbUnquote(Jsonb *jb);
 extern bool JsonbExtractScalar(JsonbContainer *jbc, JsonbValue *res);
 extern const char *JsonbTypeName(JsonbValue *val);
 
diff --git a/src/include/utils/jsonfuncs.h b/src/include/utils/jsonfuncs.h
index 31c1ae47676..190e13284b2 100644
--- a/src/include/utils/jsonfuncs.h
+++ b/src/include/utils/jsonfuncs.h
@@ -15,6 +15,7 @@
 #define JSONFUNCS_H
 
 #include "common/jsonapi.h"
+#include "nodes/nodes.h"
 #include "utils/jsonb.h"
 
 /*
@@ -88,4 +89,10 @@ extern Datum datum_to_jsonb(Datum val, JsonTypeCategory tcategory,
 							Oid outfuncoid);
 extern Datum jsonb_from_text(text *js, bool unique_keys);
 
+extern Datum json_populate_type(Datum json_val, Oid json_type,
+								Oid typid, int32 typmod,
+								void **cache, MemoryContext mcxt,
+								bool *isnull,
+								Node *escontext);
+
 #endif
diff --git a/src/include/utils/jsonpath.h b/src/include/utils/jsonpath.h
index 0f0e126e03e..0f4b1ebc9f6 100644
--- a/src/include/utils/jsonpath.h
+++ b/src/include/utils/jsonpath.h
@@ -16,6 +16,7 @@
 
 #include "fmgr.h"
 #include "nodes/pg_list.h"
+#include "nodes/primnodes.h"
 #include "utils/jsonb.h"
 
 typedef struct
@@ -202,6 +203,7 @@ 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);
 
@@ -279,4 +281,26 @@ extern bool jspConvertRegexFlags(uint32 xflags, int *result,
 								 struct Node *escontext);
 
 
+/*
+ * Evaluation of jsonpath
+ */
+
+/* External variable passed into jsonpath. */
+typedef struct JsonPathVariable
+{
+	char	   *name;
+	Oid			typid;
+	int32		typmod;
+	Datum		value;
+	bool		isnull;
+} JsonPathVariable;
+
+
+/* SQL/JSON item */
+extern bool JsonPathExists(Datum jb, JsonPath *path, bool *error, List *vars);
+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);
+
 #endif