segfaults on more then 5 queries

Debian 9.1. PostgreSQL 9.6 (also tried 9.5, 10) Latest mysql_fdw from master branch. Test foreign table:

CREATE FOREIGN TABLE public.main_address (... id character varying(64) , ... sattelite integer , ... ) SERVER my_test OPTIONS (dbname 'mon', table_name 'address'); Test function with multiple queries:

`CREATE OR REPLACE FUNCTION public.stress_test()
  RETURNS void AS
$BODY$
DECLARE
    startid integer;
    endid integer;
BEGIN
    startid := 0;
    LOOP
        startid := startid + 10;
        endid := startid + 10;
        RAISE NOTICE 'copying data from id % to id %', startid, endid;
        PERFORM id
                FROM main_address
       WHERE (sattelite = startid OR sattelite = endid);
        PERFORM pg_sleep(0.1);
    END LOOP;
 END;
$BODY$
  LANGUAGE plpgsql VOLATILE SECURITY DEFINER
  COST 100;`

Result:

SELECT public.stress_test();

NOTICE:  copying data from id 10 to id 20
CONTEXT:  function PL/pgSQL stress_test(), row 12, operator RAISE
CONTEXT:  SQL-operator : "SELECT id
                FROM main_address
        WHERE (sattelite = startid OR sattelite = endid)"
function PL/pgSQL stress_test(), row 14, operator PERFORM
NOTICE:  copying data from id 20 to id 30
CONTEXT:  function PL/pgSQL stress_test(), row 12, operator RAISE
NOTICE:  copying data from id 30 to id 40
CONTEXT:  function PL/pgSQL stress_test(), row 12, operator RAISE
NOTICE:  copying data from id 40 to id 50
CONTEXT:  function PL/pgSQL stress_test(), row 12, operator RAISE
NOTICE:  copying data from id 50 to id 60
CONTEXT:  function PL/pgSQL stress_test(), row 12, operator RAISE
NOTICE:  copying data from id 60 to id 70
CONTEXT:  function PL/pgSQL stress_test(), row 12, operator RAISE

ERROR:  cannot convert constant value to MySQL value
HINT:  Constant value data type: 0
CONTEXT:  SQL-operator: "SELECT id
                FROM main_address
        WHERE (sattelite = startid OR sattelite = endid)"
функция PL/pgSQL stress_test(), row 14, operator PERFORM
********** Error **********

ERROR: cannot convert constant value to MySQL value
SQL-condition: HV004
HINT: Constant value data type: 0
CONTEXT: SQL-operator : "SELECT id
                FROM main_address
        WHERE (sattelite = startid OR sattelite = endid)"
function PL/pgSQL stress_test(), row 14, operator PERFORM

Also in syslog I've: kernel: [8389070.645456] postgres[45009]: segfault at 10 ip 00007f74ca6484a0 sp 00007fff6e565510 error 6 in mysql_fdw.so[7f74ca63f000+d000]

On mysql server query log:

 770677 Connect  monitor@192.168.90.88 on monitoring
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Query    SET time_zone = '+00:00'
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Prepare  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 10) OR (`sattelite` = 20)))
                770677 Execute  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 10) OR (`sattelite` = 20)))
                770677 Close stmt
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Query    SET time_zone = '+00:00'
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Prepare  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 20) OR (`sattelite` = 30)))
                770677 Execute  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 20) OR (`sattelite` = 30)))
                770677 Close stmt
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Query    SET time_zone = '+00:00'
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Prepare  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 30) OR (`sattelite` = 40)))
                770677 Execute  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 30) OR (`sattelite` = 40)))
                770677 Close stmt
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Query    SET time_zone = '+00:00'
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Prepare  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 40) OR (`sattelite` = 50)))
                770677 Execute  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 40) OR (`sattelite` = 50)))
                770677 Close stmt
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Query    SET time_zone = '+00:00'
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Prepare  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 50) OR (`sattelite` = 60)))
                770677 Execute  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = 50) OR (`sattelite` = 60)))
                770677 Close stmt
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Query    SET time_zone = '+00:00'
                770677 Query    SET sql_mode='ANSI_QUOTES'
                770677 Prepare  SELECT `id` FROM `monitoring`.`address` WHERE (((`sattelite` = ?) OR (`sattelite` = ?)))

EnterpriseDB / mysql_fdw

segfaults on more then 5 queries #158