/*
 *	function.c
 *
 *	server-side function support
 *
 *	Copyright (c) 2010-2023, PostgreSQL Global Development Group
 *	src/bin/pg_upgrade/function.c
 */

#include "postgres_fe.h"

#include "access/transam.h"
#include "catalog/pg_language_d.h"
#include "pg_upgrade.h"

/*
 * qsort comparator for pointers to library names
 *
 * We sort first by name length, then alphabetically for names of the
 * same length, then database array index.  This is to ensure that, eg,
 * "hstore_plpython" sorts after both "hstore" and "plpython"; otherwise
 * transform modules will probably fail their LOAD tests.  (The backend
 * ought to cope with that consideration, but it doesn't yet, and even
 * when it does it'll still be a good idea to have a predictable order of
 * probing here.)
 */
static int
library_name_compare(const void *p1, const void *p2)
{
	const char *str1 = ((const LibraryInfo *) p1)->name;
	const char *str2 = ((const LibraryInfo *) p2)->name;
	int			slen1 = strlen(str1);
	int			slen2 = strlen(str2);
	int			cmp = strcmp(str1, str2);

	if (slen1 != slen2)
		return slen1 - slen2;
	if (cmp != 0)
		return cmp;
	else
		return ((const LibraryInfo *) p1)->dbnum -
			((const LibraryInfo *) p2)->dbnum;
}


/*
 * get_loadable_libraries()
 *
 *	Fetch the names of all old libraries containing C-language functions.
 *	We will later check that they all exist in the new installation.
 */
void
get_loadable_libraries(void)
{
	PGresult  **ress;
	int			totaltups;
	int			dbnum;

	ress = (PGresult **) pg_malloc(old_cluster.dbarr.ndbs * sizeof(PGresult *));
	totaltups = 0;

	/* Fetch all library names, removing duplicates within each DB */
	for (dbnum = 0; dbnum < old_cluster.dbarr.ndbs; dbnum++)
	{
		DbInfo	   *active_db = &old_cluster.dbarr.dbs[dbnum];
		PGconn	   *conn = connectToServer(&old_cluster, active_db->db_name);

		/*
		 * Fetch all libraries containing non-built-in C functions in this DB.
		 */
		ress[dbnum] = executeQueryOrDie(conn,
										"SELECT DISTINCT probin "
										"FROM pg_catalog.pg_proc "
										"WHERE prolang = %u AND "
										"probin IS NOT NULL AND "
										"oid >= %u;",
										ClanguageId,
										FirstNormalObjectId);
		totaltups += PQntuples(ress[dbnum]);

		PQfinish(conn);
	}

	os_info.libraries = (LibraryInfo *) pg_malloc(totaltups * sizeof(LibraryInfo));
	totaltups = 0;

	for (dbnum = 0; dbnum < old_cluster.dbarr.ndbs; dbnum++)
	{
		PGresult   *res = ress[dbnum];
		int			ntups;
		int			rowno;

		ntups = PQntuples(res);
		for (rowno = 0; rowno < ntups; rowno++)
		{
			char	   *lib = PQgetvalue(res, rowno, 0);

			os_info.libraries[totaltups].name = pg_strdup(lib);
			os_info.libraries[totaltups].dbnum = dbnum;

			totaltups++;
		}
		PQclear(res);
	}

	pg_free(ress);

	os_info.num_libraries = totaltups;
}


/*
 * check_loadable_libraries()
 *
 *	Check that the new cluster contains all required libraries.
 *	We do this by actually trying to LOAD each one, thereby testing
 *	compatibility as well as presence.
 */
void
check_loadable_libraries(void)
{
	PGconn	   *conn = connectToServer(&new_cluster, "template1");
	int			libnum;
	int			was_load_failure = false;
	FILE	   *script = NULL;
	char		output_path[MAXPGPATH];

	prep_status("Checking for presence of required libraries");

	snprintf(output_path, sizeof(output_path), "%s/%s",
			 log_opts.basedir, "loadable_libraries.txt");

	/*
	 * Now we want to sort the library names into order.  This avoids multiple
	 * probes of the same library, and ensures that libraries are probed in a
	 * consistent order, which is important for reproducible behavior if one
	 * library depends on another.
	 */
	qsort(os_info.libraries, os_info.num_libraries,
		  sizeof(LibraryInfo), library_name_compare);

	for (libnum = 0; libnum < os_info.num_libraries; libnum++)
	{
		char	   *lib = os_info.libraries[libnum].name;
		int			llen = strlen(lib);
		char		cmd[7 + 2 * MAXPGPATH + 1];
		PGresult   *res;

		/* Did the library name change?  Probe it. */
		if (libnum == 0 || strcmp(lib, os_info.libraries[libnum - 1].name) != 0)
		{
			strcpy(cmd, "LOAD '");
			PQescapeStringConn(conn, cmd + strlen(cmd), lib, llen, NULL);
			strcat(cmd, "'");

			res = PQexec(conn, cmd);

			if (PQresultStatus(res) != PGRES_COMMAND_OK)
			{
				was_load_failure = true;

				if (script == NULL && (script = fopen_priv(output_path, "w")) == NULL)
					pg_fatal("could not open file \"%s\": %s",
							 output_path, strerror(errno));
				fprintf(script, _("could not load library \"%s\": %s"),
						lib,
						PQerrorMessage(conn));
			}
			else
				was_load_failure = false;

			PQclear(res);
		}

		if (was_load_failure)
			fprintf(script, _("In database: %s\n"),
					old_cluster.dbarr.dbs[os_info.libraries[libnum].dbnum].db_name);
	}

	PQfinish(conn);

	if (script)
	{
		fclose(script);
		pg_log(PG_REPORT, "fatal");
		pg_fatal("Your installation references loadable libraries that are missing from the\n"
				 "new installation.  You can add these libraries to the new installation,\n"
				 "or remove the functions using them from the old installation.  A list of\n"
				 "problem libraries is in the file:\n"
				 "    %s", output_path);
	}
	else
		check_ok();
}
