Add more SQL/JSON constructor functions

This Patch introduces three SQL standard JSON functions:

JSON()
JSON_SCALAR()
JSON_SERIALIZE()

JSON() produces json values from text, bytea, json or jsonb values,
and has facilitites for handling duplicate keys.

JSON_SCALAR() produces a json value from any scalar sql value,
including json and jsonb.

JSON_SERIALIZE() produces text or bytea from input which containis
or represents json or jsonb;

For the most part these functions don't add any significant new
capabilities, but they will be of use to users wanting standard
compliant JSON handling.

Catversion bumped as this changes ruleutils.c.

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>

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,
Peter Eisentraut

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+HiwqE4XTdfb1nW=Ojoy_tQSRhYt-q_kb6i5d4xcKyrLC1Nbg@mail.gmail.com

4 files changed, 467 insertions, 14 deletions

diff --git a/src/interfaces/ecpg/test/expected/sql-sqljson.c b/src/interfaces/ecpg/test/expected/sql-sqljson.c
index a2c49b54f99..39221f9ea5d 100644
--- a/src/interfaces/ecpg/test/expected/sql-sqljson.c
+++ b/src/interfaces/ecpg/test/expected/sql-sqljson.c
@@ -196,6 +196,202 @@ if (sqlca.sqlcode < 0) sqlprint();}
 
   printf("Found json=%s\n", json);
 
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( null )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 42 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 42 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( '{ \"a\" : 1 } ' format json )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 45 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 45 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( '{ \"a\" : 1 } ' format json encoding UTF8 )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 48 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 48 "sqljson.pgc"
+
+  // error
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( '   1   ' :: jsonb )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 51 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 51 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( '   1   ' :: json with unique keys ) into json", ECPGt_EOIT, ECPGt_EORT);
+#line 54 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 54 "sqljson.pgc"
+
+  // error
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( '{\"a\": 1, \"a\": 2}' )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 57 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 57 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json ( '{\"a\": 1, \"a\": 2}' with unique keys )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 60 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 60 "sqljson.pgc"
+
+  // error
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( null )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 63 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 63 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( null :: int )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 66 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 66 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( 123.45 )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 69 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 69 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( true )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 72 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 72 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( ' 123.45' )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 75 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 75 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( '2020-06-07 01:02:03' :: timestamp )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 78 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 78 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_scalar ( '{}' :: jsonb )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 81 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 81 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_serialize ( null )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 84 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 84 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_serialize ( json ( '{ \"a\" : 1 } ' ) )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 87 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 87 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_serialize ( '{ \"a\" : 1 } ' )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 90 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 90 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_serialize ( '1' format json )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 93 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 93 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_serialize ( '{ \"a\" : 1 } ' returning varchar )", ECPGt_EOIT, 
+	ECPGt_char,(json),(long)1024,(long)1,(1024)*sizeof(char), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 96 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 96 "sqljson.pgc"
+
+  printf("Found json=%s\n", json);
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select json_serialize ( '{ \"a\" : 1 } ' returning jsonb )", ECPGt_EOIT, ECPGt_EORT);
+#line 99 "sqljson.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 99 "sqljson.pgc"
+
+  // error
+
   { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "with val ( js ) as ( values ( '{ \"a\": 1, \"b\": [{ \"a\": 1, \"b\": 0, \"a\": 2 }] }' ) ) select js is json \"IS JSON\" , js is not json \"IS NOT JSON\" , js is json value \"IS VALUE\" , js is json object \"IS OBJECT\" , js is json array \"IS ARRAY\" , js is json scalar \"IS SCALAR\" , js is json without unique keys \"WITHOUT UNIQUE\" , js is json with unique keys \"WITH UNIQUE\" from val", ECPGt_EOIT, 
 	ECPGt_bool,&(is_json[0]),(long)1,(long)1,sizeof(bool), 
 	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, 
@@ -213,19 +409,19 @@ if (sqlca.sqlcode < 0) sqlprint();}
 	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, 
 	ECPGt_bool,&(is_json[7]),(long)1,(long)1,sizeof(bool), 
 	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
-#line 54 "sqljson.pgc"
+#line 114 "sqljson.pgc"
 
 if (sqlca.sqlcode < 0) sqlprint();}
-#line 54 "sqljson.pgc"
+#line 114 "sqljson.pgc"
 
 	  for (int i = 0; i < sizeof(is_json); i++)
 		  printf("Found is_json[%d]: %s\n", i, is_json[i] ? "true" : "false");
 
   { ECPGdisconnect(__LINE__, "CURRENT");
-#line 58 "sqljson.pgc"
+#line 118 "sqljson.pgc"
 
 if (sqlca.sqlcode < 0) sqlprint();}
-#line 58 "sqljson.pgc"
+#line 118 "sqljson.pgc"
 
 
   return 0;
diff --git a/src/interfaces/ecpg/test/expected/sql-sqljson.stderr b/src/interfaces/ecpg/test/expected/sql-sqljson.stderr
index 1252cb3b66a..37a361156f7 100644
--- a/src/interfaces/ecpg/test/expected/sql-sqljson.stderr
+++ b/src/interfaces/ecpg/test/expected/sql-sqljson.stderr
@@ -65,27 +65,208 @@ SQL error: duplicate JSON key "1" on line 33
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_get_data on line 39: RESULT: {"1": 1} offset: -1; array: no
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_execute on line 42: query: with val ( js ) as ( values ( '{ "a": 1, "b": [{ "a": 1, "b": 0, "a": 2 }] }' ) ) select js is json "IS JSON" , js is not json "IS NOT JSON" , js is json value "IS VALUE" , js is json object "IS OBJECT" , js is json array "IS ARRAY" , js is json scalar "IS SCALAR" , js is json without unique keys "WITHOUT UNIQUE" , js is json with unique keys "WITH UNIQUE" from val; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: ecpg_execute on line 42: query: select json ( null ); with 0 parameter(s) on connection ecpg1_regression
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_execute on line 42: using PQexec
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_process_output on line 42: correctly got 1 tuples with 8 fields
+[NO_PID]: ecpg_process_output on line 42: correctly got 1 tuples with 1 fields
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: t offset: -1; array: no
+[NO_PID]: ecpg_get_data on line 42: RESULT:  offset: -1; array: no
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: f offset: -1; array: no
+[NO_PID]: raising sqlcode -213 on line 42: null value without indicator on line 42
+[NO_PID]: sqlca: code: -213, state: 22002
+SQL error: null value without indicator on line 42
+[NO_PID]: ecpg_execute on line 45: query: select json ( '{ "a" : 1 } ' format json ); with 0 parameter(s) on connection ecpg1_regression
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: t offset: -1; array: no
+[NO_PID]: ecpg_execute on line 45: using PQexec
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: t offset: -1; array: no
+[NO_PID]: ecpg_process_output on line 45: correctly got 1 tuples with 1 fields
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: f offset: -1; array: no
+[NO_PID]: ecpg_get_data on line 45: RESULT: { "a" : 1 }  offset: -1; array: no
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: f offset: -1; array: no
+[NO_PID]: ecpg_execute on line 48: query: select json ( '{ "a" : 1 } ' format json encoding UTF8 ); with 0 parameter(s) on connection ecpg1_regression
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: t offset: -1; array: no
+[NO_PID]: ecpg_execute on line 48: using PQexec
 [NO_PID]: sqlca: code: 0, state: 00000
-[NO_PID]: ecpg_get_data on line 42: RESULT: f offset: -1; array: no
+[NO_PID]: ecpg_check_PQresult on line 48: bad response - ERROR:  JSON ENCODING clause is only allowed for bytea input type
+LINE 1: select json ( '{ "a" : 1 } ' format json encoding UTF8 )
+                                     ^
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlstate 42804 (sqlcode -400): JSON ENCODING clause is only allowed for bytea input type on line 48
+[NO_PID]: sqlca: code: -400, state: 42804
+SQL error: JSON ENCODING clause is only allowed for bytea input type on line 48
+[NO_PID]: ecpg_execute on line 51: query: select json ( '   1   ' :: jsonb ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 51: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 51: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 51: RESULT: 1 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 54: query: select json ( '   1   ' :: json with unique keys ) into json; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 54: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_check_PQresult on line 54: bad response - ERROR:  cannot use non-string types with WITH UNIQUE KEYS clause
+LINE 1: select json ( '   1   ' :: json with unique keys ) into json
+               ^
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlstate 42804 (sqlcode -400): cannot use non-string types with WITH UNIQUE KEYS clause on line 54
+[NO_PID]: sqlca: code: -400, state: 42804
+SQL error: cannot use non-string types with WITH UNIQUE KEYS clause on line 54
+[NO_PID]: ecpg_execute on line 57: query: select json ( '{"a": 1, "a": 2}' ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 57: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 57: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 57: RESULT: {"a": 1, "a": 2} offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 60: query: select json ( '{"a": 1, "a": 2}' with unique keys ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 60: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_check_PQresult on line 60: bad response - ERROR:  duplicate JSON object key value
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlstate 22030 (sqlcode -400): duplicate JSON object key value on line 60
+[NO_PID]: sqlca: code: -400, state: 22030
+SQL error: duplicate JSON object key value on line 60
+[NO_PID]: ecpg_execute on line 63: query: select json_scalar ( null ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 63: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 63: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 63: RESULT:  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlcode -213 on line 63: null value without indicator on line 63
+[NO_PID]: sqlca: code: -213, state: 22002
+SQL error: null value without indicator on line 63
+[NO_PID]: ecpg_execute on line 66: query: select json_scalar ( null :: int ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 66: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 66: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 66: RESULT:  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlcode -213 on line 66: null value without indicator on line 66
+[NO_PID]: sqlca: code: -213, state: 22002
+SQL error: null value without indicator on line 66
+[NO_PID]: ecpg_execute on line 69: query: select json_scalar ( 123.45 ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 69: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 69: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 69: RESULT: 123.45 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 72: query: select json_scalar ( true ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 72: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 72: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 72: RESULT: true offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 75: query: select json_scalar ( ' 123.45' ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 75: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 75: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 75: RESULT: " 123.45" offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 78: query: select json_scalar ( '2020-06-07 01:02:03' :: timestamp ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 78: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 78: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 78: RESULT: "2020-06-07T01:02:03" offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 81: query: select json_scalar ( '{}' :: jsonb ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 81: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 81: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 81: RESULT: {} offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 84: query: select json_serialize ( null ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 84: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 84: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 84: RESULT:  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlcode -213 on line 84: null value without indicator on line 84
+[NO_PID]: sqlca: code: -213, state: 22002
+SQL error: null value without indicator on line 84
+[NO_PID]: ecpg_execute on line 87: query: select json_serialize ( json ( '{ "a" : 1 } ' ) ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 87: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 87: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 87: RESULT: { "a" : 1 }  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 90: query: select json_serialize ( '{ "a" : 1 } ' ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 90: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 90: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 90: RESULT: { "a" : 1 }  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 93: query: select json_serialize ( '1' format json ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 93: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 93: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 93: RESULT: 1 offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 96: query: select json_serialize ( '{ "a" : 1 } ' returning varchar ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 96: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 96: correctly got 1 tuples with 1 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 96: RESULT: { "a" : 1 }  offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 99: query: select json_serialize ( '{ "a" : 1 } ' returning jsonb ); with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 99: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_check_PQresult on line 99: bad response - ERROR:  cannot use RETURNING type jsonb in JSON_SERIALIZE()
+HINT:  Try returning a string type or bytea.
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: raising sqlstate 42804 (sqlcode -400): cannot use RETURNING type jsonb in JSON_SERIALIZE() on line 99
+[NO_PID]: sqlca: code: -400, state: 42804
+SQL error: cannot use RETURNING type jsonb in JSON_SERIALIZE() on line 99
+[NO_PID]: ecpg_execute on line 102: query: with val ( js ) as ( values ( '{ "a": 1, "b": [{ "a": 1, "b": 0, "a": 2 }] }' ) ) select js is json "IS JSON" , js is not json "IS NOT JSON" , js is json value "IS VALUE" , js is json object "IS OBJECT" , js is json array "IS ARRAY" , js is json scalar "IS SCALAR" , js is json without unique keys "WITHOUT UNIQUE" , js is json with unique keys "WITH UNIQUE" from val; with 0 parameter(s) on connection ecpg1_regression
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_execute on line 102: using PQexec
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_process_output on line 102: correctly got 1 tuples with 8 fields
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: t offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: f offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: t offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: t offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: f offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: f offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: t offset: -1; array: no
+[NO_PID]: sqlca: code: 0, state: 00000
+[NO_PID]: ecpg_get_data on line 102: RESULT: f offset: -1; array: no
 [NO_PID]: sqlca: code: 0, state: 00000
 [NO_PID]: ecpg_finish: connection ecpg1_regression closed
 [NO_PID]: sqlca: code: 0, state: 00000
diff --git a/src/interfaces/ecpg/test/expected/sql-sqljson.stdout b/src/interfaces/ecpg/test/expected/sql-sqljson.stdout
index 558901c4068..83f8df13e5a 100644
--- a/src/interfaces/ecpg/test/expected/sql-sqljson.stdout
+++ b/src/interfaces/ecpg/test/expected/sql-sqljson.stdout
@@ -4,6 +4,22 @@ Found json=[]
 Found json=[]
 Found json={"1" : 1, "1" : "2"}
 Found json={"1": 1}
+Found json={"1": 1}
+Found json={ "a" : 1 } 
+Found json=1
+Found json={"a": 1, "a": 2}
+Found json={"a": 1, "a": 2}
+Found json={"a": 1, "a": 2}
+Found json=123.45
+Found json=true
+Found json=" 123.45"
+Found json="2020-06-07T01:02:03"
+Found json={}
+Found json={}
+Found json={ "a" : 1 } 
+Found json={ "a" : 1 } 
+Found json=1
+Found json={ "a" : 1 } 
 Found is_json[0]: true
 Found is_json[1]: false
 Found is_json[2]: true
diff --git a/src/interfaces/ecpg/test/sql/sqljson.pgc b/src/interfaces/ecpg/test/sql/sqljson.pgc
index a0055038344..ddcbcc3b3cb 100644
--- a/src/interfaces/ecpg/test/sql/sqljson.pgc
+++ b/src/interfaces/ecpg/test/sql/sqljson.pgc
@@ -39,6 +39,66 @@ EXEC SQL END DECLARE SECTION;
   EXEC SQL SELECT JSON_OBJECT(1: 1, '2': NULL ABSENT ON NULL WITHOUT UNIQUE RETURNING jsonb) INTO :json;
   printf("Found json=%s\n", json);
 
+  EXEC SQL SELECT JSON(NULL) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON('{ "a" : 1 } ' FORMAT JSON) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON('{ "a" : 1 } ' FORMAT JSON ENCODING UTF8) INTO :json;
+  // error
+
+  EXEC SQL SELECT JSON('   1   '::jsonb) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON('   1   '::json WITH UNIQUE KEYS) INTO json;
+  // error
+
+  EXEC SQL SELECT JSON('{"a": 1, "a": 2}') INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON('{"a": 1, "a": 2}' WITH UNIQUE KEYS) INTO :json;
+  // error
+
+  EXEC SQL SELECT JSON_SCALAR(NULL) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SCALAR(NULL::int) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SCALAR(123.45) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SCALAR(true) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SCALAR(' 123.45') INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SCALAR('2020-06-07 01:02:03'::timestamp) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SCALAR('{}'::jsonb) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SERIALIZE(NULL) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SERIALIZE(JSON('{ "a" : 1 } ')) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SERIALIZE('{ "a" : 1 } ') INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SERIALIZE('1' FORMAT JSON) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SERIALIZE('{ "a" : 1 } ' RETURNING varchar) INTO :json;
+  printf("Found json=%s\n", json);
+
+  EXEC SQL SELECT JSON_SERIALIZE('{ "a" : 1 } ' RETURNING jsonb);
+  // error
+
   EXEC SQL WITH val (js) AS (VALUES ('{ "a": 1, "b": [{ "a": 1, "b": 0, "a": 2 }] }'))
 	  SELECT
 	  js IS JSON "IS JSON",