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funcapi.h
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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) 2002-2021, 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 */
39 
40  /* array of attribute type input function finfo */
42 
43  /* array of attribute type i/o parameter OIDs */
45 
46  /* array of attribute typmod */
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  */
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  */
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  */
113 
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 
156  Oid *resultTypeId,
157  TupleDesc *resultTupleDesc);
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(char prokind,
176  Datum proargnames, Datum proargmodes,
177  char ***arg_names);
178 
179 extern int get_func_trftypes(HeapTuple procTup, Oid **p_trftypes);
180 extern char *get_func_result_name(Oid functionId);
181 
182 extern TupleDesc build_function_result_tupdesc_d(char prokind,
183  Datum proallargtypes,
184  Datum proargmodes,
185  Datum proargnames);
187 
188 
189 /*----------
190  * Support to ease writing functions returning composite types
191  *
192  * External declarations:
193  * TupleDesc BlessTupleDesc(TupleDesc tupdesc) - "Bless" a completed tuple
194  * descriptor so that it can be used to return properly labeled tuples.
195  * You need to call this if you are going to use heap_form_tuple directly.
196  * TupleDescGetAttInMetadata does it for you, however, so no need to call
197  * it if you call TupleDescGetAttInMetadata.
198  * AttInMetadata *TupleDescGetAttInMetadata(TupleDesc tupdesc) - Build an
199  * AttInMetadata struct based on the given TupleDesc. AttInMetadata can
200  * be used in conjunction with C strings to produce a properly formed
201  * tuple.
202  * HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values) -
203  * build a HeapTuple given user data in C string form. values is an array
204  * of C strings, one for each attribute of the return tuple.
205  * Datum HeapTupleHeaderGetDatum(HeapTupleHeader tuple) - convert a
206  * HeapTupleHeader to a Datum.
207  *
208  * Macro declarations:
209  * HeapTupleGetDatum(HeapTuple tuple) - convert a HeapTuple to a Datum.
210  *
211  * Obsolete routines and macros:
212  * TupleDesc RelationNameGetTupleDesc(const char *relname) - Use to get a
213  * TupleDesc based on a named relation.
214  * TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases) - Use to get a
215  * TupleDesc based on a type OID.
216  * TupleGetDatum(TupleTableSlot *slot, HeapTuple tuple) - get a Datum
217  * given a tuple and a slot.
218  *----------
219  */
220 
221 #define HeapTupleGetDatum(tuple) HeapTupleHeaderGetDatum((tuple)->t_data)
222 /* obsolete version of above */
223 #define TupleGetDatum(_slot, _tuple) HeapTupleGetDatum(_tuple)
224 
225 extern TupleDesc RelationNameGetTupleDesc(const char *relname);
226 extern TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases);
227 
228 /* from execTuples.c */
231 extern HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values);
233 
234 
235 /*----------
236  * Support for Set Returning Functions (SRFs)
237  *
238  * The basic API for SRFs using ValuePerCall mode looks something like this:
239  *
240  * Datum
241  * my_Set_Returning_Function(PG_FUNCTION_ARGS)
242  * {
243  * FuncCallContext *funcctx;
244  * Datum result;
245  * MemoryContext oldcontext;
246  * <user defined declarations>
247  *
248  * if (SRF_IS_FIRSTCALL())
249  * {
250  * funcctx = SRF_FIRSTCALL_INIT();
251  * // switch context when allocating stuff to be used in later calls
252  * oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
253  * <user defined code>
254  * <if returning composite>
255  * <build TupleDesc, and perhaps AttInMetadata>
256  * <endif returning composite>
257  * <user defined code>
258  * // return to original context when allocating transient memory
259  * MemoryContextSwitchTo(oldcontext);
260  * }
261  * <user defined code>
262  * funcctx = SRF_PERCALL_SETUP();
263  * <user defined code>
264  *
265  * if (funcctx->call_cntr < funcctx->max_calls)
266  * {
267  * <user defined code>
268  * <obtain result Datum>
269  * SRF_RETURN_NEXT(funcctx, result);
270  * }
271  * else
272  * SRF_RETURN_DONE(funcctx);
273  * }
274  *
275  * NOTE: there is no guarantee that a SRF using ValuePerCall mode will be
276  * run to completion; for example, a query with LIMIT might stop short of
277  * fetching all the rows. Therefore, do not expect that you can do resource
278  * cleanup just before SRF_RETURN_DONE(). You need not worry about releasing
279  * memory allocated in multi_call_memory_ctx, but holding file descriptors or
280  * other non-memory resources open across calls is a bug. SRFs that need
281  * such resources should not use these macros, but instead populate a
282  * tuplestore during a single call, and return that using SFRM_Materialize
283  * mode (see fmgr/README). Alternatively, set up a callback to release
284  * resources at query shutdown, using RegisterExprContextCallback().
285  *
286  *----------
287  */
288 
289 /* from funcapi.c */
292 extern void end_MultiFuncCall(PG_FUNCTION_ARGS, FuncCallContext *funcctx);
293 
294 #define SRF_IS_FIRSTCALL() (fcinfo->flinfo->fn_extra == NULL)
295 
296 #define SRF_FIRSTCALL_INIT() init_MultiFuncCall(fcinfo)
297 
298 #define SRF_PERCALL_SETUP() per_MultiFuncCall(fcinfo)
299 
300 #define SRF_RETURN_NEXT(_funcctx, _result) \
301  do { \
302  ReturnSetInfo *rsi; \
303  (_funcctx)->call_cntr++; \
304  rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
305  rsi->isDone = ExprMultipleResult; \
306  PG_RETURN_DATUM(_result); \
307  } while (0)
308 
309 #define SRF_RETURN_NEXT_NULL(_funcctx) \
310  do { \
311  ReturnSetInfo *rsi; \
312  (_funcctx)->call_cntr++; \
313  rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
314  rsi->isDone = ExprMultipleResult; \
315  PG_RETURN_NULL(); \
316  } while (0)
317 
318 #define SRF_RETURN_DONE(_funcctx) \
319  do { \
320  ReturnSetInfo *rsi; \
321  end_MultiFuncCall(fcinfo, _funcctx); \
322  rsi = (ReturnSetInfo *) fcinfo->resultinfo; \
323  rsi->isDone = ExprEndResult; \
324  PG_RETURN_NULL(); \
325  } while (0)
326 
327 /*----------
328  * Support to ease writing of functions dealing with VARIADIC inputs
329  *----------
330  *
331  * This function extracts a set of argument values, types and NULL markers
332  * for a given input function. This returns a set of data:
333  * - **values includes the set of Datum values extracted.
334  * - **types the data type OID for each element.
335  * - **nulls tracks if an element is NULL.
336  *
337  * variadic_start indicates the argument number where the VARIADIC argument
338  * starts.
339  * convert_unknown set to true will enforce the conversion of arguments
340  * with unknown data type to text.
341  *
342  * The return result is the number of elements stored, or -1 in the case of
343  * "VARIADIC NULL".
344  */
345 extern int extract_variadic_args(FunctionCallInfo fcinfo, int variadic_start,
346  bool convert_unknown, Datum **values,
347  Oid **types, bool **nulls);
348 
349 #endif /* FUNCAPI_H */
uint64 call_cntr
Definition: funcapi.h:65
int get_func_input_arg_names(char prokind, Datum proargnames, Datum proargmodes, char ***arg_names)
Definition: funcapi.c:1411
Definition: fmgr.h:56
Datum HeapTupleHeaderGetDatum(HeapTupleHeader tuple)
Definition: execTuples.c:2205
struct typedefs * types
Definition: ecpg.c:29
int get_func_trftypes(HeapTuple procTup, Oid **p_trftypes)
Definition: funcapi.c:1363
TupleDesc build_function_result_tupdesc_t(HeapTuple procTuple)
Definition: funcapi.c:1603
TupleDesc get_expr_result_tupdesc(Node *expr, bool noError)
Definition: funcapi.c:440
TypeFuncClass get_call_result_type(FunctionCallInfo fcinfo, Oid *resultTypeId, TupleDesc *resultTupleDesc)
Definition: funcapi.c:207
Definition: nodes.h:528
TupleDesc build_function_result_tupdesc_d(char prokind, Datum proallargtypes, Datum proargmodes, Datum proargnames)
Definition: funcapi.c:1653
int32 * atttypmods
Definition: funcapi.h:47
int get_func_arg_info(HeapTuple procTup, Oid **p_argtypes, char ***p_argnames, char **p_argmodes)
Definition: funcapi.c:1268
NameData relname
Definition: pg_class.h:38
unsigned int Oid
Definition: postgres_ext.h:31
Oid * attioparams
Definition: funcapi.h:44
TupleDesc tuple_desc
Definition: funcapi.h:112
signed int int32
Definition: c.h:417
TupleDesc TypeGetTupleDesc(Oid typeoid, List *colaliases)
Definition: funcapi.c:1806
TupleDesc RelationNameGetTupleDesc(const char *relname)
Definition: funcapi.c:1773
AttInMetadata * attinmeta
Definition: funcapi.h:91
TupleDesc tupdesc
Definition: funcapi.h:38
struct FuncCallContext FuncCallContext
TypeFuncClass
Definition: funcapi.h:146
void end_MultiFuncCall(PG_FUNCTION_ARGS, FuncCallContext *funcctx)
Definition: funcapi.c:151
FuncCallContext * init_MultiFuncCall(PG_FUNCTION_ARGS)
Definition: funcapi.c:64
struct AttInMetadata AttInMetadata
uintptr_t Datum
Definition: postgres.h:367
TypeFuncClass get_expr_result_type(Node *expr, Oid *resultTypeId, TupleDesc *resultTupleDesc)
Definition: funcapi.c:223
TypeFuncClass get_func_result_type(Oid functionId, Oid *resultTypeId, TupleDesc *resultTupleDesc)
Definition: funcapi.c:300
TupleDesc BlessTupleDesc(TupleDesc tupdesc)
Definition: execTuples.c:2052
MemoryContext multi_call_memory_ctx
Definition: funcapi.h:101
char * get_func_result_name(Oid functionId)
Definition: funcapi.c:1499
FuncCallContext * per_MultiFuncCall(PG_FUNCTION_ARGS)
Definition: funcapi.c:139
AttInMetadata * TupleDescGetAttInMetadata(TupleDesc tupdesc)
Definition: execTuples.c:2067
static Datum values[MAXATTR]
Definition: bootstrap.c:165
void * user_fctx
Definition: funcapi.h:82
bool resolve_polymorphic_argtypes(int numargs, Oid *argtypes, char *argmodes, Node *call_expr)
Definition: funcapi.c:953
#define PG_FUNCTION_ARGS
Definition: fmgr.h:193
HeapTuple BuildTupleFromCStrings(AttInMetadata *attinmeta, char **values)
Definition: execTuples.c:2116
FmgrInfo * attinfuncs
Definition: funcapi.h:41
int extract_variadic_args(FunctionCallInfo fcinfo, int variadic_start, bool convert_unknown, Datum **values, Oid **types, bool **nulls)
Definition: funcapi.c:1908
Definition: pg_list.h:50
uint64 max_calls
Definition: funcapi.h:74