src/include/funcapi.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * funcapi.h
   4  *        Definitions for functions which return composite type and/or sets
   5  *
   6  * This file must be included by all Postgres modules that either define
   7  * or call FUNCAPI-callable functions or macros.
   8  *
   9  *
  10  * Copyright (c) 2002-2008, PostgreSQL Global Development Group
  11  *
  12  * $PostgreSQL$
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16 #ifndef FUNCAPI_H
  17 #define FUNCAPI_H
  18
  19 #include "fmgr.h"
  20 #include "access/tupdesc.h"
  21 #include "executor/executor.h"
  22 #include "executor/tuptable.h"
  23
  24
  25 /*-------------------------------------------------------------------------
  26  *      Support to ease writing Functions returning composite types
  27  *-------------------------------------------------------------------------
  28  *
  29  * This struct holds arrays of individual attribute information
  30  * needed to create a tuple from raw C strings. It also requires
  31  * a copy of the TupleDesc. The information carried here
  32  * is derived from the TupleDesc, but it is stored here to
  33  * avoid redundant cpu cycles on each call to an SRF.
  34  */
  35 typedef struct AttInMetadata
  36 {
  37         /* full TupleDesc */
  38         TupleDesc       tupdesc;
  39
  40         /* array of attribute type input function finfo */
  41         FmgrInfo   *attinfuncs;
  42
  43         /* array of attribute type i/o parameter OIDs */
  44         Oid                *attioparams;
  45
  46         /* array of attribute typmod */
  47         int32      *atttypmods;
  48 } AttInMetadata;
  49
  50 /*-------------------------------------------------------------------------
  51  *              Support struct to ease writing Set Returning Functions (SRFs)
  52  *-------------------------------------------------------------------------
  53  *
  54  * This struct holds function context for Set Returning Functions.
  55  * Use fn_extra to hold a pointer to it across calls
  56  */
  57 typedef struct FuncCallContext
  58 {
  59         /*
  60          * Number of times we've been called before
  61          *
  62          * call_cntr is initialized to 0 for you by SRF_FIRSTCALL_INIT(), and
  63          * incremented for you every time SRF_RETURN_NEXT() is called.
  64          */
  65         uint32          call_cntr;
  66
  67         /*
  68          * OPTIONAL maximum number of calls
  69          *
  70          * max_calls is here for convenience only and setting it is optional. If
  71          * not set, you must provide alternative means to know when the function
  72          * is done.
  73          */
  74         uint32          max_calls;
  75
  76         /*
  77          * OPTIONAL pointer to result slot
  78          *
  79          * This is obsolete and only present for backwards compatibility, viz,
  80          * user-defined SRFs that use the deprecated TupleDescGetSlot().
  81          */
  82         TupleTableSlot *slot;
  83
  84         /*
  85          * OPTIONAL pointer to miscellaneous user-provided context information
  86          *
  87          * user_fctx is for use as a pointer to your own struct to retain
  88          * arbitrary context information between calls of your function.
  89          */
  90         void       *user_fctx;
  91
  92         /*
  93          * OPTIONAL pointer to struct containing attribute type input metadata
  94          *
  95          * attinmeta is for use when returning tuples (i.e. composite data types)
  96          * and is not used when returning base data types. It is only needed if
  97          * you intend to use BuildTupleFromCStrings() to create the return tuple.
  98          */
  99         AttInMetadata *attinmeta;
 100
 101         /*
 102          * memory context used for structures that must live for multiple calls
 103          *
 104          * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used
 105          * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory
 106          * context for any memory that is to be reused across multiple calls of
 107          * the SRF.
 108          */
 109         MemoryContext multi_call_memory_ctx;
 110
 111         /*
 112          * OPTIONAL pointer to struct containing tuple description
 113          *
 114          * tuple_desc is for use when returning tuples (i.e. composite data types)
 115          * and is only needed if you are going to build the tuples with
 116          * heap_form_tuple() rather than with BuildTupleFromCStrings(). Note that
 117          * the TupleDesc pointer stored here should usually have been run through
 118          * BlessTupleDesc() first.
 119          */
 120         TupleDesc       tuple_desc;
 121
 122 } FuncCallContext;
 123
 124 /*----------
 125  *      Support to ease writing functions returning composite types
 126  *
 127  * External declarations:
 128  * get_call_result_type:
 129  *              Given a function's call info record, determine the kind of datatype
 130  *              it is supposed to return.  If resultTypeId isn't NULL, *resultTypeId
 131  *              receives the actual datatype OID (this is mainly useful for scalar
 132  *              result types).  If resultTupleDesc isn't NULL, *resultTupleDesc
 133  *              receives a pointer to a TupleDesc when the result is of a composite
 134  *              type, or NULL when it's a scalar result or the rowtype could not be
 135  *              determined.  NB: the tupledesc should be copied if it is to be
 136  *              accessed over a long period.
 137  * get_expr_result_type:
 138  *              Given an expression node, return the same info as for
 139  *              get_call_result_type.  Note: the cases in which rowtypes cannot be
 140  *              determined are different from the cases for get_call_result_type.
 141  * get_func_result_type:
 142  *              Given only a function's OID, return the same info as for
 143  *              get_call_result_type.  Note: the cases in which rowtypes cannot be
 144  *              determined are different from the cases for get_call_result_type.
 145  *              Do *not* use this if you can use one of the others.
 146  *----------
 147  */
 148
 149 /* Type categories for get_call_result_type and siblings */
 150 typedef enum TypeFuncClass
 151 {
 152         TYPEFUNC_SCALAR,                        /* scalar result type */
 153         TYPEFUNC_COMPOSITE,                     /* determinable rowtype result */
 154         TYPEFUNC_RECORD,                        /* indeterminate rowtype result */
 155         TYPEFUNC_OTHER                          /* bogus type, eg pseudotype */
 156 } TypeFuncClass;
 157
 158 extern TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,
 159                                          Oid *resultTypeId,
 160                                          TupleDesc *resultTupleDesc);
 161 extern TypeFuncClass get_expr_result_type(Node *expr,
 162                                          Oid *resultTypeId,
 163                                          TupleDesc *resultTupleDesc);
 164 extern TypeFuncClass get_func_result_type(Oid functionId,
 165                                          Oid *resultTypeId,
 166                                          TupleDesc *resultTupleDesc);
 167
 168 extern bool resolve_polymorphic_argtypes(int numargs, Oid *argtypes,
 169                                                          char *argmodes,
 170                                                          Node *call_expr);
 171
 172 extern int get_func_arg_info(HeapTuple procTup,
 173                                   Oid **p_argtypes, char ***p_argnames,
 174                                   char **p_argmodes);
 175
 176 extern char *get_func_result_name(Oid functionId);
 177
 178 extern TupleDesc build_function_result_tupdesc_d(Datum proallargtypes,
 179                                                                 Datum proargmodes,
 180                                                                 Datum proargnames);
 181 extern TupleDesc build_function_result_tupdesc_t(HeapTuple procTuple);
 182
 183
 184 /*----------
 185  *      Support to ease writing functions returning composite types
 186  *
 187  * External declarations:
 188  * TupleDesc BlessTupleDesc(TupleDesc tupdesc) - "Bless" a completed tuple
 189  *              descriptor so that it can be used to return properly labeled tuples.
 190  *              You need to call this if you are going to use heap_form_tuple directly.
 191  *              TupleDescGetAttInMetadata does it for you, however, so no need to call
 192  *              it if you call TupleDescGetAttInMetadata.
 193  * AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc) - Build an
 194  *              AttInMetadata struct based on the given TupleDesc. AttInMetadata can
 195  *              be used in conjunction with C strings to produce a properly formed
 196  *              tuple.
 197  * HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values) -
 198  *              build a HeapTuple given user data in C string form. values is an array
 199  *              of C strings, one for each attribute of the return tuple.
 200  *
 201  * Macro declarations:
 202  * HeapTupleGetDatum(HeapTuple tuple) - convert a HeapTuple to a Datum.
 203  *
 204  * Obsolete routines and macros:
 205  * TupleDesc RelationNameGetTupleDesc(const char *relname) - Use to get a
 206  *              TupleDesc based on a named relation.
 207  * TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases) - Use to get a
 208  *              TupleDesc based on a type OID.
 209  * TupleTableSlot *TupleDescGetSlot(TupleDesc tupdesc) - Builds a
 210  *              TupleTableSlot, which is not needed anymore.
 211  * TupleGetDatum(TupleTableSlot *slot, HeapTuple tuple) - get a Datum
 212  *              given a tuple and a slot.
 213  *----------
 214  */
 215
 216 #define HeapTupleGetDatum(_tuple)               PointerGetDatum((_tuple)->t_data)
 217 /* obsolete version of above */
 218 #define TupleGetDatum(_slot, _tuple)    PointerGetDatum((_tuple)->t_data)
 219
 220 extern TupleDesc RelationNameGetTupleDesc(const char *relname);
 221 extern TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases);
 222
 223 /* from execTuples.c */
 224 extern TupleDesc BlessTupleDesc(TupleDesc tupdesc);
 225 extern AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc);
 226 extern HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values);
 227 extern TupleTableSlot *TupleDescGetSlot(TupleDesc tupdesc);
 228
 229
 230 /*----------
 231  *              Support for Set Returning Functions (SRFs)
 232  *
 233  * The basic API for SRFs looks something like:
 234  *
 235  * Datum
 236  * my_Set_Returning_Function(PG_FUNCTION_ARGS)
 237  * {
 238  *      FuncCallContext    *funcctx;
 239  *      Datum                           result;
 240  *      MemoryContext           oldcontext;
 241  *      <user defined declarations>
 242  *
 243  *      if (SRF_IS_FIRSTCALL())
 244  *      {
 245  *              funcctx = SRF_FIRSTCALL_INIT();
 246  *              // switch context when allocating stuff to be used in later calls
 247  *              oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 248  *              <user defined code>
 249  *              <if returning composite>
 250  *                      <build TupleDesc, and perhaps AttInMetaData>
 251  *              <endif returning composite>
 252  *              <user defined code>
 253  *              // return to original context when allocating transient memory
 254  *              MemoryContextSwitchTo(oldcontext);
 255  *      }
 256  *      <user defined code>
 257  *      funcctx = SRF_PERCALL_SETUP();
 258  *      <user defined code>
 259  *
 260  *      if (funcctx->call_cntr < funcctx->max_calls)
 261  *      {
 262  *              <user defined code>
 263  *              <obtain result Datum>
 264  *              SRF_RETURN_NEXT(funcctx, result);
 265  *      }
 266  *      else
 267  *              SRF_RETURN_DONE(funcctx);
 268  * }
 269  *
 270  *----------
 271  */
 272
 273 /* from funcapi.c */
 274 extern FuncCallContext *init_MultiFuncCall(PG_FUNCTION_ARGS);
 275 extern FuncCallContext *per_MultiFuncCall(PG_FUNCTION_ARGS);
 276 extern void end_MultiFuncCall(PG_FUNCTION_ARGS, FuncCallContext *funcctx);
 277
 278 #define SRF_IS_FIRSTCALL() (fcinfo->flinfo->fn_extra == NULL)
 279
 280 #define SRF_FIRSTCALL_INIT() init_MultiFuncCall(fcinfo)
 281
 282 #define SRF_PERCALL_SETUP() per_MultiFuncCall(fcinfo)
 283
 284 #define SRF_RETURN_NEXT(_funcctx, _result) \
 285         do { \
 286                 ReturnSetInfo      *rsi; \
 287                 (_funcctx)->call_cntr++; \
 288                 rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
 289                 rsi->isDone = ExprMultipleResult; \
 290                 PG_RETURN_DATUM(_result); \
 291         } while (0)
 292
 293 #define  SRF_RETURN_DONE(_funcctx) \
 294         do { \
 295                 ReturnSetInfo      *rsi; \
 296                 end_MultiFuncCall(fcinfo, _funcctx); \
 297                 rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
 298                 rsi->isDone = ExprEndResult; \
 299                 PG_RETURN_NULL(); \
 300         } while (0)
 301
 302 #endif   /* FUNCAPI_H */