Chapter 44. Server Programming Interface
Table of Contents
- 44.1. Interface Functions
- SPI_connect — connect a procedure to the SPI manager
- SPI_finish — disconnect a procedure from the SPI manager
- SPI_execute — execute a command
- SPI_exec — execute a read/write command
- SPI_execute_with_args — execute a command with out-of-line parameters
- SPI_prepare — prepare a statement, without executing it yet
- SPI_prepare_cursor — prepare a statement, without executing it yet
- SPI_prepare_params — prepare a statement, without executing it yet
- SPI_getargcount — return the number of arguments needed by a statement prepared by
SPI_prepare- SPI_getargtypeid — return the data type OID for an argument of a statement prepared by
SPI_prepare- SPI_is_cursor_plan — return
trueif a statement prepared bySPI_preparecan be used withSPI_cursor_open- SPI_execute_plan — execute a statement prepared by
SPI_prepare- SPI_execute_plan_with_paramlist — execute a statement prepared by
SPI_prepare- SPI_execp — execute a statement in read/write mode
- SPI_cursor_open — set up a cursor using a statement created with
SPI_prepare- SPI_cursor_open_with_args — set up a cursor using a query and parameters
- SPI_cursor_open_with_paramlist — set up a cursor using parameters
- SPI_cursor_find — find an existing cursor by name
- SPI_cursor_fetch — fetch some rows from a cursor
- SPI_cursor_move — move a cursor
- SPI_scroll_cursor_fetch — fetch some rows from a cursor
- SPI_scroll_cursor_move — move a cursor
- SPI_cursor_close — close a cursor
- SPI_keepplan — save a prepared statement
- SPI_saveplan — save a prepared statement
- SPI_register_relation — make an ephemeral named relation available by name in SPI queries
- SPI_unregister_relation — remove an ephemeral named relation from the registry
- SPI_register_trigger_data — make ephemeral trigger data available in SPI queries
- SPI_finish — disconnect a procedure from the SPI manager
- SPI_connect — connect a procedure to the SPI manager
- 44.2. Interface Support Functions
- SPI_fname — determine the column name for the specified column number
- SPI_fnumber — determine the column number for the specified column name
- SPI_getvalue — return the string value of the specified column
- SPI_getbinval — return the binary value of the specified column
- SPI_gettype — return the data type name of the specified column
- SPI_gettypeid — return the data type OID of the specified column
- SPI_getrelname — return the name of the specified relation
- SPI_getnspname — return the namespace of the specified relation
- SPI_fnumber — determine the column number for the specified column name
- SPI_fname — determine the column name for the specified column number
- 44.3. Memory Management
- SPI_palloc — allocate memory in the upper executor context
- SPI_repalloc — reallocate memory in the upper executor context
- SPI_pfree — free memory in the upper executor context
- SPI_copytuple — make a copy of a row in the upper executor context
- SPI_returntuple — prepare to return a tuple as a Datum
- SPI_modifytuple — create a row by replacing selected fields of a given row
- SPI_freetuple — free a row allocated in the upper executor context
- SPI_freetuptable — free a row set created by
SPI_executeor a similar function- SPI_freeplan — free a previously saved prepared statement
- SPI_repalloc — reallocate memory in the upper executor context
- SPI_palloc — allocate memory in the upper executor context
- 44.4. Visibility of Data Changes
- 44.5. Examples
The Server Programming Interface (SPI) gives writers of user-defined C functions the ability to run SQL commands inside their functions. SPI is a set of interface functions to simplify access to the parser, planner, and executor. SPI also does some memory management.
Note
The available procedural languages provide various means to execute SQL commands from procedures. Most of these facilities are based on SPI, so this documentation might be of use for users of those languages as well.
To avoid misunderstanding we'll use the term “function” when we speak of SPI interface functions and “procedure” for a user-defined C-function that is using SPI.
Note that if a command invoked via SPI fails, then control will not be returned to your procedure. Rather, the transaction or subtransaction in which your procedure executes will be rolled back. (This might seem surprising given that the SPI functions mostly have documented error-return conventions. Those conventions only apply for errors detected within the SPI functions themselves, however.) It is possible to recover control after an error by establishing your own subtransaction surrounding SPI calls that might fail.
SPI functions return a nonnegative result on success (either via a returned integer value or in the global variable SPI_result, as described below). On error, a negative result or NULL will be returned.
Source code files that use SPI must include the header file executor/spi.h.