/*------------------------------------------------------------------------- * * funcapi.h * Definitions for functions which return composite type and/or sets * * This file must be included by all Postgres modules that either define * or call FUNCAPI-callable functions or macros. * * * Copyright (c) 2002-2005, PostgreSQL Global Development Group * * $PostgreSQL: pgsql/src/include/funcapi.h,v 1.15 2005/01/01 05:43:08 momjian Exp $ * *------------------------------------------------------------------------- */ #ifndef FUNCAPI_H #define FUNCAPI_H #include "fmgr.h" #include "access/tupdesc.h" #include "executor/executor.h" #include "executor/tuptable.h" /*------------------------------------------------------------------------- * Support to ease writing Functions returning composite types *------------------------------------------------------------------------- * * This struct holds arrays of individual attribute information * needed to create a tuple from raw C strings. It also requires * a copy of the TupleDesc. The information carried here * is derived from the TupleDesc, but it is stored here to * avoid redundant cpu cycles on each call to an SRF. */ typedef struct AttInMetadata { /* full TupleDesc */ TupleDesc tupdesc; /* array of attribute type input function finfo */ FmgrInfo *attinfuncs; /* array of attribute type i/o parameter OIDs */ Oid *attioparams; /* array of attribute typmod */ int32 *atttypmods; } AttInMetadata; /*------------------------------------------------------------------------- * Support struct to ease writing Set Returning Functions (SRFs) *------------------------------------------------------------------------- * * This struct holds function context for Set Returning Functions. * Use fn_extra to hold a pointer to it across calls */ typedef struct FuncCallContext { /* * Number of times we've been called before * * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and * incremented for you every time SRF_RETURN_NEXT() is called. */ uint32 call_cntr; /* * OPTIONAL maximum number of calls * * max_calls is here for convenience only and setting it is optional. If * not set, you must provide alternative means to know when the * function is done. */ uint32 max_calls; /* * OPTIONAL pointer to result slot * * This is obsolete and only present for backwards compatibility, viz, * user-defined SRFs that use the deprecated TupleDescGetSlot(). */ TupleTableSlot *slot; /* * OPTIONAL pointer to miscellaneous user-provided context information * * user_fctx is for use as a pointer to your own struct to retain * arbitrary context information between calls of your function. */ void *user_fctx; /* * OPTIONAL pointer to struct containing attribute type input metadata * * attinmeta is for use when returning tuples (i.e. composite data types) * and is not used when returning base data types. It is only needed * if you intend to use BuildTupleFromCStrings() to create the return * tuple. */ AttInMetadata *attinmeta; /* * memory context used for structures that must live for multiple * calls * * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory * context for any memory that is to be reused across multiple calls * of the SRF. */ MemoryContext multi_call_memory_ctx; /* * OPTIONAL pointer to struct containing tuple description * * tuple_desc is for use when returning tuples (i.e. composite data * types) and is only needed if you are going to build the tuples with * heap_formtuple() rather than with BuildTupleFromCStrings(). Note * that the TupleDesc pointer stored here should usually have been run * through BlessTupleDesc() first. */ TupleDesc tuple_desc; } FuncCallContext; /*---------- * Support to ease writing Functions returning composite types * * External declarations: * TupleDesc RelationNameGetTupleDesc(const char *relname) - Use to get a * TupleDesc based on a specified relation. * TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases) - Use to get a * TupleDesc based on a type OID. This can be used to get * a TupleDesc for a base (scalar) or composite (relation) type. * TupleDesc BlessTupleDesc(TupleDesc tupdesc) - "Bless" a completed tuple * descriptor so that it can be used to return properly labeled tuples. * You need to call this if you are going to use heap_formtuple directly. * TupleDescGetAttInMetadata does it for you, however, so no need to call * it if you call TupleDescGetAttInMetadata. * AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc) - Build an * AttInMetadata struct based on the given TupleDesc. AttInMetadata can * be used in conjunction with C strings to produce a properly formed * tuple. * HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values) - * build a HeapTuple given user data in C string form. values is an array * of C strings, one for each attribute of the return tuple. * * Macro declarations: * HeapTupleGetDatum(HeapTuple tuple) - convert a HeapTuple to a Datum. * * Obsolete routines and macros: * TupleTableSlot *TupleDescGetSlot(TupleDesc tupdesc) - Builds a * TupleTableSlot, which is not needed anymore. * TupleGetDatum(TupleTableSlot *slot, HeapTuple tuple) - get a Datum * given a tuple and a slot. *---------- */ #define HeapTupleGetDatum(_tuple) PointerGetDatum((_tuple)->t_data) /* obsolete version of above */ #define TupleGetDatum(_slot, _tuple) PointerGetDatum((_tuple)->t_data) /* from tupdesc.c */ extern TupleDesc RelationNameGetTupleDesc(const char *relname); extern TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases); /* from execTuples.c */ extern TupleDesc BlessTupleDesc(TupleDesc tupdesc); extern AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc); extern HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values); extern TupleTableSlot *TupleDescGetSlot(TupleDesc tupdesc); /*---------- * Support for Set Returning Functions (SRFs) * * The basic API for SRFs looks something like: * * Datum * my_Set_Returning_Function(PG_FUNCTION_ARGS) * { * FuncCallContext *funcctx; * Datum result; * MemoryContext oldcontext; * * * if (SRF_IS_FIRSTCALL()) * { * funcctx = SRF_FIRSTCALL_INIT(); * // switch context when allocating stuff to be used in later calls * oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx); * * * * * * // return to original context when allocating transient memory * MemoryContextSwitchTo(oldcontext); * } * * funcctx = SRF_PERCALL_SETUP(); * * * if (funcctx->call_cntr < funcctx->max_calls) * { * * * SRF_RETURN_NEXT(funcctx, result); * } * else * SRF_RETURN_DONE(funcctx); * } * *---------- */ /* from funcapi.c */ extern FuncCallContext *init_MultiFuncCall(PG_FUNCTION_ARGS); extern FuncCallContext *per_MultiFuncCall(PG_FUNCTION_ARGS); extern void end_MultiFuncCall(PG_FUNCTION_ARGS, FuncCallContext *funcctx); #define SRF_IS_FIRSTCALL() (fcinfo->flinfo->fn_extra == NULL) #define SRF_FIRSTCALL_INIT() init_MultiFuncCall(fcinfo) #define SRF_PERCALL_SETUP() per_MultiFuncCall(fcinfo) #define SRF_RETURN_NEXT(_funcctx, _result) \ do { \ ReturnSetInfo *rsi; \ (_funcctx)->call_cntr++; \ rsi = (ReturnSetInfo *) fcinfo->resultinfo; \ rsi->isDone = ExprMultipleResult; \ PG_RETURN_DATUM(_result); \ } while (0) #define SRF_RETURN_DONE(_funcctx) \ do { \ ReturnSetInfo *rsi; \ end_MultiFuncCall(fcinfo, _funcctx); \ rsi = (ReturnSetInfo *) fcinfo->resultinfo; \ rsi->isDone = ExprEndResult; \ PG_RETURN_NULL(); \ } while (0) #endif /* FUNCAPI_H */