SPI_EXECUTE(3)						  PostgreSQL 9.2.7 Documentation					    SPI_EXECUTE(3)

NAME

       SPI_execute - execute a command

SYNOPSIS

       int SPI_execute(const char * command, bool read_only, long count)

DESCRIPTION

       SPI_execute executes the specified SQL command for count rows. If read_only is true, the command must be read-only, and execution overhead
       is somewhat reduced.

       This function can only be called from a connected procedure.

       If count is zero then the command is executed for all rows that it applies to. If count is greater than zero, then no more than count rows
       will be retrieved; execution stops when the count is reached, much like adding a LIMIT clause to the query. For example,

	   SPI_execute("SELECT * FROM foo", true, 5);

       will retrieve at most 5 rows from the table. Note that such a limit is only effective when the command actually returns rows. For example,

	   SPI_execute("INSERT INTO foo SELECT * FROM bar", false, 5);

       inserts all rows from bar, ignoring the count parameter. However, with

	   SPI_execute("INSERT INTO foo SELECT * FROM bar RETURNING *", false, 5);

       at most 5 rows would be inserted, since execution would stop after the fifth RETURNING result row is retrieved.

       You can pass multiple commands in one string; SPI_execute returns the result for the command executed last. The count limit applies to each
       command separately (even though only the last result will actually be returned). The limit is not applied to any hidden commands generated
       by rules.

       When read_only is false, SPI_execute increments the command counter and computes a new snapshot before executing each command in the
       string. The snapshot does not actually change if the current transaction isolation level is SERIALIZABLE or REPEATABLE READ, but in READ
       COMMITTED mode the snapshot update allows each command to see the results of newly committed transactions from other sessions. This is
       essential for consistent behavior when the commands are modifying the database.

       When read_only is true, SPI_execute does not update either the snapshot or the command counter, and it allows only plain SELECT commands to
       appear in the command string. The commands are executed using the snapshot previously established for the surrounding query. This execution
       mode is somewhat faster than the read/write mode due to eliminating per-command overhead. It also allows genuinely stable functions to be
       built: since successive executions will all use the same snapshot, there will be no change in the results.

       It is generally unwise to mix read-only and read-write commands within a single function using SPI; that could result in very confusing
       behavior, since the read-only queries would not see the results of any database updates done by the read-write queries.

       The actual number of rows for which the (last) command was executed is returned in the global variable SPI_processed. If the return value
       of the function is SPI_OK_SELECT, SPI_OK_INSERT_RETURNING, SPI_OK_DELETE_RETURNING, or SPI_OK_UPDATE_RETURNING, then you can use the global
       pointer SPITupleTable *SPI_tuptable to access the result rows. Some utility commands (such as EXPLAIN) also return row sets, and
       SPI_tuptable will contain the result in these cases too.

       The structure SPITupleTable is defined thus:

	   typedef struct
	   {
	       MemoryContext tuptabcxt;    /* memory context of result table */
	       uint32	   alloced;	   /* number of alloced vals */
	       uint32	   free;	   /* number of free vals */
	       TupleDesc   tupdesc;	   /* row descriptor */
	       HeapTuple  *vals;	   /* rows */
	   } SPITupleTable;

       vals is an array of pointers to rows. (The number of valid entries is given by SPI_processed.)  tupdesc is a row descriptor which you can
       pass to SPI functions dealing with rows.  tuptabcxt, alloced, and free are internal fields not intended for use by SPI callers.

       SPI_finish frees all SPITupleTables allocated during the current procedure. You can free a particular result table earlier, if you are done
       with it, by calling SPI_freetuptable.

ARGUMENTS

       const char * command
	   string containing command to execute

       bool read_only
	   true for read-only execution

       long count
	   maximum number of rows to return, or 0 for no limit

RETURN VALUE

       If the execution of the command was successful then one of the following (nonnegative) values will be returned:

       SPI_OK_SELECT
	   if a SELECT (but not SELECT INTO) was executed

       SPI_OK_SELINTO
	   if a SELECT INTO was executed

       SPI_OK_INSERT
	   if an INSERT was executed

       SPI_OK_DELETE
	   if a DELETE was executed

       SPI_OK_UPDATE
	   if an UPDATE was executed

       SPI_OK_INSERT_RETURNING
	   if an INSERT RETURNING was executed

       SPI_OK_DELETE_RETURNING
	   if a DELETE RETURNING was executed

       SPI_OK_UPDATE_RETURNING
	   if an UPDATE RETURNING was executed

       SPI_OK_UTILITY
	   if a utility command (e.g., CREATE TABLE) was executed

       SPI_OK_REWRITTEN
	   if the command was rewritten into another kind of command (e.g., UPDATE became an INSERT) by a rule.

       On error, one of the following negative values is returned:

       SPI_ERROR_ARGUMENT
	   if command is NULL or count is less than 0

       SPI_ERROR_COPY
	   if COPY TO stdout or COPY FROM stdin was attempted

       SPI_ERROR_TRANSACTION
	   if a transaction manipulation command was attempted (BEGIN, COMMIT, ROLLBACK, SAVEPOINT, PREPARE TRANSACTION, COMMIT PREPARED, ROLLBACK
	   PREPARED, or any variant thereof)

       SPI_ERROR_OPUNKNOWN
	   if the command type is unknown (shouldn't happen)

       SPI_ERROR_UNCONNECTED
	   if called from an unconnected procedure

NOTES

       All SPI query-execution functions set both SPI_processed and SPI_tuptable (just the pointer, not the contents of the structure). Save these
       two global variables into local procedure variables if you need to access the result table of SPI_execute or another query-execution
       function across later calls.

PostgreSQL 9.2.7						    2014-02-17							    SPI_EXECUTE(3)