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SPI_exec

Name

SPI_exec --  Creates an execution plan (parser+planner+optimizer) and executes a query.

Synopsis

SPI_exec(query, tcount)

Inputs

char *query

String containing query plan

int tcount

Maximum number of tuples to return

Outputs

int
SPI_ERROR_UNCONNECTED if called from an un-connected procedure
SPI_ERROR_ARGUMENT if query is NULL or tcount < 0.
SPI_ERROR_UNCONNECTED if procedure is unconnected.
SPI_ERROR_COPY if COPY TO/FROM stdin.
SPI_ERROR_CURSOR if DECLARE/CLOSE CURSOR, FETCH.
SPI_ERROR_TRANSACTION if BEGIN/ABORT/END.
SPI_ERROR_OPUNKNOWN if type of query is unknown (this shouldn't occur).

If execution of your query was successful then one of the following (non-negative) values will be returned:

SPI_OK_UTILITY if some utility (e.g. CREATE TABLE ...) was executed
SPI_OK_SELECT if SELECT (but not SELECT ... INTO!) was executed
SPI_OK_SELINTO if SELECT ... INTO was executed
SPI_OK_INSERT if INSERT (or INSERT ... SELECT) was executed
SPI_OK_DELETE if DELETE was executed
SPI_OK_UPDATE if UPDATE was executed

Description

SPI_exec creates an execution plan (parser+planner+optimizer) and executes the query for tcount tuples.

Usage

This should only be called from a connected procedure. If tcount is zero then it executes the query for all tuples returned by the query scan. Using tcount > 0 you may restrict the number of tuples for which the query will be executed (much like a LIMIT clause). For example,

SPI_exec ("INSERT INTO tab SELECT * FROM tab", 5);

will allow at most 5 tuples to be inserted into table. If execution of your query was successful then a non-negative value will be returned.

Note: You may pass multiple queries in one string or query string may be re-written by RULEs. SPI_exec returns the result for the last query executed.

The actual number of tuples for which the (last) query was executed is returned in the global variable SPI_processed (if not SPI_OK_UTILITY). If SPI_OK_SELECT is returned and SPI_processed > 0 then you may use global pointer SPITupleTable *SPI_tuptable to access the result tuples.

SPI_exec may return one of the following (negative) values:

SPI_ERROR_ARGUMENT if query is NULL or tcount < 0.
SPI_ERROR_UNCONNECTED if procedure is unconnected.
SPI_ERROR_COPY if COPY TO/FROM stdin.
SPI_ERROR_CURSOR if DECLARE/CLOSE CURSOR, FETCH.
SPI_ERROR_TRANSACTION if BEGIN/ABORT/END.
SPI_ERROR_OPUNKNOWN if type of query is unknown (this shouldn't occur).

Structures

If SPI_OK_SELECT is returned and SPI_processed > 0 then you may use the global pointer SPITupleTable *SPI_tuptable to access the selected tuples.

Structure SPITupleTable is defined in spi.h:

   typedef struct
   {
       MemoryContext tuptabcxt;    /* memory context of result table */
       uint32      alloced;        /* # of alloced vals */
       uint32      free;           /* # of free vals */
       TupleDesc   tupdesc;        /* tuple descriptor */
       HeapTuple  *vals;           /* tuples */
   } SPITupleTable;

vals is an array of pointers to tuples (the number of useful entries is given by SPI_processed). TupleDesc tupdesc is a tuple descriptor which you may pass to SPI functions dealing with tuples. tuptabcxt, alloced, and free are internal fields not intended for use by SPI callers.

Note: Functions SPI_exec, SPI_execp and SPI_prepare change 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 of one SPI_exec or SPI_execp across later calls.

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.

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