| PostgreSQL 7.4.30 Documentation | ||||
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   SPI_prepare creates and returns an execution
   plan for the specified command but doesn't execute the command.
   This function should only be called from a connected procedure.
  
   When the same or a similar command is to be executed repeatedly, it
   may be advantageous to perform the planning only once.
   SPI_prepare converts a command string into an
   execution plan that can be executed repeatedly using
   SPI_execp.
  
   A prepared command can be generalized by writing parameters
   ($1, $2, etc.) in place of what would be
   constants in a normal command.  The actual values of the parameters
   are then specified when SPI_execp is called.
   This allows the prepared command to be used over a wider range of
   situations than would be possible without parameters.
  
   The plan returned by SPI_prepare can be used
   only in the current invocation of the procedure since
   SPI_finish frees memory allocated for a plan.
   But a plan can be saved for longer using the function
   SPI_saveplan.
  
command string
number of input parameters ($1, $2, etc.)
pointer to an array containing the OIDs of the data types of the parameters
   SPI_prepare returns non-null pointer to an
   execution plan.  On error, NULL will be returned.
   In both cases, SPI_result will be set analogous
   to the value returned by SPI_exec, except that
   it is set to SPI_ERROR_ARGUMENT if
   command is NULL, or if
   nargs is less than 0, or if nargs is
   greater than 0 and argtypes is NULL.