Note: At present, this section is just taken from PostgreSQL documentation and is subject to revision for Postgres-XC.
   SPI_exec is the same as
   SPI_execute, with the latter's
   read_only parameter always taken as
   false.
  
Note: At present, this section is just taken from PostgreSQL documentation and is subject to revision for Postgres-XC.
string containing command to execute
maximum number of rows to return, or 0 for no limit