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1 : /*-------------------------------------------------------------------------
2 : *
3 : * funcapi.h
4 : * Definitions for functions which return composite type and/or sets
5 : * or work on VARIADIC inputs.
6 : *
7 : * This file must be included by all Postgres modules that either define
8 : * or call FUNCAPI-callable functions or macros.
9 : *
10 : *
11 : * Copyright (c) 2002-2026, PostgreSQL Global Development Group
12 : *
13 : * src/include/funcapi.h
14 : *
15 : *-------------------------------------------------------------------------
16 : */
17 : #ifndef FUNCAPI_H
18 : #define FUNCAPI_H
19 :
20 : #include "access/tupdesc.h"
21 : #include "executor/executor.h"
22 : #include "executor/tuptable.h"
23 : #include "fmgr.h"
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 : uint64 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 : uint64 max_calls;
75 :
76 : /*
77 : * OPTIONAL pointer to miscellaneous user-provided context information
78 : *
79 : * user_fctx is for use as a pointer to your own struct to retain
80 : * arbitrary context information between calls of your function.
81 : */
82 : void *user_fctx;
83 :
84 : /*
85 : * OPTIONAL pointer to struct containing attribute type input metadata
86 : *
87 : * attinmeta is for use when returning tuples (i.e. composite data types)
88 : * and is not used when returning base data types. It is only needed if
89 : * you intend to use BuildTupleFromCStrings() to create the return tuple.
90 : */
91 : AttInMetadata *attinmeta;
92 :
93 : /*
94 : * memory context used for structures that must live for multiple calls
95 : *
96 : * multi_call_memory_ctx is set by SRF_FIRSTCALL_INIT() for you, and used
97 : * by SRF_RETURN_DONE() for cleanup. It is the most appropriate memory
98 : * context for any memory that is to be reused across multiple calls of
99 : * the SRF.
100 : */
101 : MemoryContext multi_call_memory_ctx;
102 :
103 : /*
104 : * OPTIONAL pointer to struct containing tuple description
105 : *
106 : * tuple_desc is for use when returning tuples (i.e. composite data types)
107 : * and is only needed if you are going to build the tuples with
108 : * heap_form_tuple() rather than with BuildTupleFromCStrings(). Note that
109 : * the TupleDesc pointer stored here should usually have been run through
110 : * BlessTupleDesc() first.
111 : */
112 : TupleDesc tuple_desc;
113 :
114 : } FuncCallContext;
115 :
116 : /*----------
117 : * Support to ease writing functions returning composite types
118 : *
119 : * External declarations:
120 : * get_call_result_type:
121 : * Given a function's call info record, determine the kind of datatype
122 : * it is supposed to return. If resultTypeId isn't NULL, *resultTypeId
123 : * receives the actual datatype OID (this is mainly useful for scalar
124 : * result types). If resultTupleDesc isn't NULL, *resultTupleDesc
125 : * receives a pointer to a TupleDesc when the result is of a composite
126 : * type, or NULL when it's a scalar result or the rowtype could not be
127 : * determined. NB: the tupledesc should be copied if it is to be
128 : * accessed over a long period.
129 : * get_expr_result_type:
130 : * Given an expression node, return the same info as for
131 : * get_call_result_type. Note: the cases in which rowtypes cannot be
132 : * determined are different from the cases for get_call_result_type.
133 : * get_func_result_type:
134 : * Given only a function's OID, return the same info as for
135 : * get_call_result_type. Note: the cases in which rowtypes cannot be
136 : * determined are different from the cases for get_call_result_type.
137 : * Do *not* use this if you can use one of the others.
138 : *
139 : * See also get_expr_result_tupdesc(), which is a convenient wrapper around
140 : * get_expr_result_type() for use when the caller only cares about
141 : * determinable-rowtype cases.
142 : *----------
143 : */
144 :
145 : /* Type categories for get_call_result_type and siblings */
146 : typedef enum TypeFuncClass
147 : {
148 : TYPEFUNC_SCALAR, /* scalar result type */
149 : TYPEFUNC_COMPOSITE, /* determinable rowtype result */
150 : TYPEFUNC_COMPOSITE_DOMAIN, /* domain over determinable rowtype result */
151 : TYPEFUNC_RECORD, /* indeterminate rowtype result */
152 : TYPEFUNC_OTHER, /* bogus type, eg pseudotype */
153 : } TypeFuncClass;
154 :
155 : extern TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo,
156 : Oid *resultTypeId,
157 : TupleDesc *resultTupleDesc);
158 : extern TypeFuncClass get_expr_result_type(Node *expr,
159 : Oid *resultTypeId,
160 : TupleDesc *resultTupleDesc);
161 : extern TypeFuncClass get_func_result_type(Oid functionId,
162 : Oid *resultTypeId,
163 : TupleDesc *resultTupleDesc);
164 :
165 : extern TupleDesc get_expr_result_tupdesc(Node *expr, bool noError);
166 :
167 : extern bool resolve_polymorphic_argtypes(int numargs, Oid *argtypes,
168 : char *argmodes,
169 : Node *call_expr);
170 :
171 : extern int get_func_arg_info(HeapTuple procTup,
172 : Oid **p_argtypes, char ***p_argnames,
173 : char **p_argmodes);
174 :
175 : extern int get_func_input_arg_names(Datum proargnames, Datum proargmodes,
176 : char ***arg_names);
177 :
178 : extern int get_func_trftypes(HeapTuple procTup, Oid **p_trftypes);
179 : extern char *get_func_result_name(Oid functionId);
180 :
181 : extern TupleDesc build_function_result_tupdesc_d(char prokind,
182 : Datum proallargtypes,
183 : Datum proargmodes,
184 : Datum proargnames);
185 : extern TupleDesc build_function_result_tupdesc_t(HeapTuple procTuple);
186 :
187 :
188 : /*----------
189 : * Support to ease writing functions returning composite types
190 : *
191 : * External declarations:
192 : * TupleDesc BlessTupleDesc(TupleDesc tupdesc) - "Bless" a completed tuple
193 : * descriptor so that it can be used to return properly labeled tuples.
194 : * You need to call this if you are going to use heap_form_tuple directly.
195 : * TupleDescGetAttInMetadata does it for you, however, so no need to call
196 : * it if you call TupleDescGetAttInMetadata.
197 : * AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc) - Build an
198 : * AttInMetadata struct based on the given TupleDesc. AttInMetadata can
199 : * be used in conjunction with C strings to produce a properly formed
200 : * tuple.
201 : * HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values) -
202 : * build a HeapTuple given user data in C string form. values is an array
203 : * of C strings, one for each attribute of the return tuple.
204 : * Datum HeapTupleHeaderGetDatum(HeapTupleHeader tuple) - convert a
205 : * HeapTupleHeader to a Datum.
206 : *
207 : * Inline declarations:
208 : * HeapTupleGetDatum(HeapTuple tuple) - convert a HeapTuple to a Datum.
209 : *
210 : * Obsolete routines and macros:
211 : * TupleDesc RelationNameGetTupleDesc(const char *relname) - Use to get a
212 : * TupleDesc based on a named relation.
213 : * TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases) - Use to get a
214 : * TupleDesc based on a type OID.
215 : * TupleGetDatum(TupleTableSlot *slot, HeapTuple tuple) - get a Datum
216 : * given a tuple and a slot.
217 : *----------
218 : */
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 Datum HeapTupleHeaderGetDatum(HeapTupleHeader tuple);
228 :
229 : static inline Datum
230 1143653 : HeapTupleGetDatum(const HeapTupleData *tuple)
231 : {
232 1143653 : return HeapTupleHeaderGetDatum(tuple->t_data);
233 : }
234 :
235 : /* obsolete version of above */
236 : #define TupleGetDatum(_slot, _tuple) HeapTupleGetDatum(_tuple)
237 :
238 :
239 : /*----------
240 : * Support for Set Returning Functions (SRFs)
241 : *
242 : * The basic API for SRFs using ValuePerCall mode looks something like this:
243 : *
244 : * Datum
245 : * my_Set_Returning_Function(PG_FUNCTION_ARGS)
246 : * {
247 : * FuncCallContext *funcctx;
248 : * Datum result;
249 : * MemoryContext oldcontext;
250 : * <user defined declarations>
251 : *
252 : * if (SRF_IS_FIRSTCALL())
253 : * {
254 : * funcctx = SRF_FIRSTCALL_INIT();
255 : * // switch context when allocating stuff to be used in later calls
256 : * oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
257 : * <user defined code>
258 : * <if returning composite>
259 : * <build TupleDesc, and perhaps AttInMetadata>
260 : * <endif returning composite>
261 : * <user defined code>
262 : * // return to original context when allocating transient memory
263 : * MemoryContextSwitchTo(oldcontext);
264 : * }
265 : * <user defined code>
266 : * funcctx = SRF_PERCALL_SETUP();
267 : * <user defined code>
268 : *
269 : * if (funcctx->call_cntr < funcctx->max_calls)
270 : * {
271 : * <user defined code>
272 : * <obtain result Datum>
273 : * SRF_RETURN_NEXT(funcctx, result);
274 : * }
275 : * else
276 : * SRF_RETURN_DONE(funcctx);
277 : * }
278 : *
279 : * NOTE: there is no guarantee that a SRF using ValuePerCall mode will be
280 : * run to completion; for example, a query with LIMIT might stop short of
281 : * fetching all the rows. Therefore, do not expect that you can do resource
282 : * cleanup just before SRF_RETURN_DONE(). You need not worry about releasing
283 : * memory allocated in multi_call_memory_ctx, but holding file descriptors or
284 : * other non-memory resources open across calls is a bug. SRFs that need
285 : * such resources should not use these macros, but instead populate a
286 : * tuplestore during a single call, as set up by InitMaterializedSRF() (see
287 : * fmgr/README). Alternatively, set up a callback to release resources
288 : * at query shutdown, using RegisterExprContextCallback().
289 : *
290 : *----------
291 : */
292 :
293 : /* from funcapi.c */
294 :
295 : /* flag bits for InitMaterializedSRF() */
296 : #define MAT_SRF_USE_EXPECTED_DESC 0x01 /* use expectedDesc as tupdesc. */
297 : #define MAT_SRF_BLESS 0x02 /* "Bless" a tuple descriptor with
298 : * BlessTupleDesc(). */
299 : extern void InitMaterializedSRF(FunctionCallInfo fcinfo, bits32 flags);
300 :
301 : extern FuncCallContext *init_MultiFuncCall(PG_FUNCTION_ARGS);
302 : extern FuncCallContext *per_MultiFuncCall(PG_FUNCTION_ARGS);
303 : extern void end_MultiFuncCall(PG_FUNCTION_ARGS, FuncCallContext *funcctx);
304 :
305 : #define SRF_IS_FIRSTCALL() (fcinfo->flinfo->fn_extra == NULL)
306 :
307 : #define SRF_FIRSTCALL_INIT() init_MultiFuncCall(fcinfo)
308 :
309 : #define SRF_PERCALL_SETUP() per_MultiFuncCall(fcinfo)
310 :
311 : #define SRF_RETURN_NEXT(_funcctx, _result) \
312 : do { \
313 : ReturnSetInfo *rsi; \
314 : (_funcctx)->call_cntr++; \
315 : rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
316 : rsi->isDone = ExprMultipleResult; \
317 : PG_RETURN_DATUM(_result); \
318 : } while (0)
319 :
320 : #define SRF_RETURN_NEXT_NULL(_funcctx) \
321 : do { \
322 : ReturnSetInfo *rsi; \
323 : (_funcctx)->call_cntr++; \
324 : rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
325 : rsi->isDone = ExprMultipleResult; \
326 : PG_RETURN_NULL(); \
327 : } while (0)
328 :
329 : #define SRF_RETURN_DONE(_funcctx) \
330 : do { \
331 : ReturnSetInfo *rsi; \
332 : end_MultiFuncCall(fcinfo, _funcctx); \
333 : rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
334 : rsi->isDone = ExprEndResult; \
335 : PG_RETURN_NULL(); \
336 : } while (0)
337 :
338 : /*----------
339 : * Support to ease writing of functions dealing with VARIADIC inputs
340 : *----------
341 : *
342 : * This function extracts a set of argument values, types and NULL markers
343 : * for a given input function. This returns a set of data:
344 : * - **values includes the set of Datum values extracted.
345 : * - **types the data type OID for each element.
346 : * - **nulls tracks if an element is NULL.
347 : *
348 : * variadic_start indicates the argument number where the VARIADIC argument
349 : * starts.
350 : * convert_unknown set to true will enforce the conversion of arguments
351 : * with unknown data type to text.
352 : *
353 : * The return result is the number of elements stored, or -1 in the case of
354 : * "VARIADIC NULL".
355 : */
356 : extern int extract_variadic_args(FunctionCallInfo fcinfo, int variadic_start,
357 : bool convert_unknown, Datum **args,
358 : Oid **types, bool **nulls);
359 :
360 : #endif /* FUNCAPI_H */
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