Add basic JSON_TABLE() functionality

JSON_TABLE() allows JSON data to be converted into a relational view
and thus used, for example, in a FROM clause, like other tabular
data.  Data to show in the view is selected from a source JSON object
using a JSON path expression to get a sequence of JSON objects that's
called a "row pattern", which becomes the source to compute the
SQL/JSON values that populate the view's output columns.  Column
values themselves are computed using JSON path expressions applied to
each of the JSON objects comprising the "row pattern", for which the
SQL/JSON query functions added in 6185c9737cf4 are used.

To implement JSON_TABLE() as a table function, this augments the
TableFunc and TableFuncScanState nodes that are currently used to
support XMLTABLE() with some JSON_TABLE()-specific fields.

Note that the JSON_TABLE() spec includes NESTED COLUMNS and PLAN
clauses, which are required to provide more flexibility to extract
data out of nested JSON objects, but they are not implemented here
to keep this commit of manageable size.

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: 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

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

1 files changed, 143 insertions, 0 deletions

diff --git a/src/interfaces/ecpg/test/expected/sql-sqljson_jsontable.c b/src/interfaces/ecpg/test/expected/sql-sqljson_jsontable.c
new file mode 100644
index 00000000000..42a1b176e72
--- /dev/null
+++ b/src/interfaces/ecpg/test/expected/sql-sqljson_jsontable.c
@@ -0,0 +1,143 @@
+/* Processed by ecpg (regression mode) */
+/* These include files are added by the preprocessor */
+#include <ecpglib.h>
+#include <ecpgerrno.h>
+#include <sqlca.h>
+/* End of automatic include section */
+#define ECPGdebug(X,Y) ECPGdebug((X)+100,(Y))
+
+#line 1 "sqljson_jsontable.pgc"
+#include <stdio.h>
+
+
+#line 1 "sqlca.h"
+#ifndef POSTGRES_SQLCA_H
+#define POSTGRES_SQLCA_H
+
+#ifndef PGDLLIMPORT
+#if  defined(WIN32) || defined(__CYGWIN__)
+#define PGDLLIMPORT __declspec (dllimport)
+#else
+#define PGDLLIMPORT
+#endif							/* __CYGWIN__ */
+#endif							/* PGDLLIMPORT */
+
+#define SQLERRMC_LEN	150
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+struct sqlca_t
+{
+	char		sqlcaid[8];
+	long		sqlabc;
+	long		sqlcode;
+	struct
+	{
+		int			sqlerrml;
+		char		sqlerrmc[SQLERRMC_LEN];
+	}			sqlerrm;
+	char		sqlerrp[8];
+	long		sqlerrd[6];
+	/* Element 0: empty						*/
+	/* 1: OID of processed tuple if applicable			*/
+	/* 2: number of rows processed				*/
+	/* after an INSERT, UPDATE or				*/
+	/* DELETE statement					*/
+	/* 3: empty						*/
+	/* 4: empty						*/
+	/* 5: empty						*/
+	char		sqlwarn[8];
+	/* Element 0: set to 'W' if at least one other is 'W'	*/
+	/* 1: if 'W' at least one character string		*/
+	/* value was truncated when it was			*/
+	/* stored into a host variable.             */
+
+	/*
+	 * 2: if 'W' a (hopefully) non-fatal notice occurred
+	 */	/* 3: empty */
+	/* 4: empty						*/
+	/* 5: empty						*/
+	/* 6: empty						*/
+	/* 7: empty						*/
+
+	char		sqlstate[5];
+};
+
+struct sqlca_t *ECPGget_sqlca(void);
+
+#ifndef POSTGRES_ECPG_INTERNAL
+#define sqlca (*ECPGget_sqlca())
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+#line 3 "sqljson_jsontable.pgc"
+
+
+#line 1 "regression.h"
+
+
+
+
+
+
+#line 4 "sqljson_jsontable.pgc"
+
+
+/* exec sql whenever sqlerror  sqlprint ; */
+#line 6 "sqljson_jsontable.pgc"
+
+
+int
+main ()
+{
+/* exec sql begin declare section */
+   
+
+#line 12 "sqljson_jsontable.pgc"
+ int foo ;
+/* exec sql end declare section */
+#line 13 "sqljson_jsontable.pgc"
+
+
+  ECPGdebug (1, stderr);
+
+  { ECPGconnect(__LINE__, 0, "ecpg1_regression" , NULL, NULL , NULL, 0); 
+#line 17 "sqljson_jsontable.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 17 "sqljson_jsontable.pgc"
+
+  { ECPGsetcommit(__LINE__, "on", NULL);
+#line 18 "sqljson_jsontable.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 18 "sqljson_jsontable.pgc"
+
+
+  { ECPGdo(__LINE__, 0, 1, NULL, 0, ECPGst_normal, "select foo from json_table ( jsonb '[{\"foo\":1}]' , '$[*]' as p0 columns ( foo int ) ) jt ( foo )", ECPGt_EOIT, 
+	ECPGt_int,&(foo),(long)1,(long)1,sizeof(int), 
+	ECPGt_NO_INDICATOR, NULL , 0L, 0L, 0L, ECPGt_EORT);
+#line 23 "sqljson_jsontable.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 23 "sqljson_jsontable.pgc"
+
+  printf("Found foo=%d\n", foo);
+
+  { ECPGdisconnect(__LINE__, "CURRENT");
+#line 26 "sqljson_jsontable.pgc"
+
+if (sqlca.sqlcode < 0) sqlprint();}
+#line 26 "sqljson_jsontable.pgc"
+
+
+  return 0;
+}