PostgreSQL Source Code  git master
moddatetime.c
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1 /*
2 moddatetime.c
3 
4 contrib/spi/moddatetime.c
5 
6 What is this?
7 It is a function to be called from a trigger for the purpose of updating
8 a modification datetime stamp in a record when that record is UPDATEd.
9 
10 Credits
11 This is 95%+ based on autoinc.c, which I used as a starting point as I do
12 not really know what I am doing. I also had help from
13 Jan Wieck <jwieck@debis.com> who told me about the timestamp_in("now") function.
14 OH, me, I'm Terry Mackintosh <terry@terrym.com>
15 */
16 #include "postgres.h"
17 
18 #include "access/htup_details.h"
19 #include "catalog/pg_type.h"
20 #include "executor/spi.h"
21 #include "commands/trigger.h"
22 #include "utils/builtins.h"
23 #include "utils/rel.h"
24 
26 
28 
29 Datum
31 {
32  TriggerData *trigdata = (TriggerData *) fcinfo->context;
33  Trigger *trigger; /* to get trigger name */
34  int nargs; /* # of arguments */
35  int attnum; /* positional number of field to change */
36  Oid atttypid; /* type OID of field to change */
37  Datum newdt; /* The current datetime. */
38  bool newdtnull; /* null flag for it */
39  char **args; /* arguments */
40  char *relname; /* triggered relation name */
41  Relation rel; /* triggered relation */
42  HeapTuple rettuple = NULL;
43  TupleDesc tupdesc; /* tuple description */
44 
45  if (!CALLED_AS_TRIGGER(fcinfo))
46  /* internal error */
47  elog(ERROR, "moddatetime: not fired by trigger manager");
48 
49  if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event))
50  /* internal error */
51  elog(ERROR, "moddatetime: must be fired for row");
52 
53  if (!TRIGGER_FIRED_BEFORE(trigdata->tg_event))
54  /* internal error */
55  elog(ERROR, "moddatetime: must be fired before event");
56 
57  if (TRIGGER_FIRED_BY_INSERT(trigdata->tg_event))
58  /* internal error */
59  elog(ERROR, "moddatetime: cannot process INSERT events");
60  else if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
61  rettuple = trigdata->tg_newtuple;
62  else
63  /* internal error */
64  elog(ERROR, "moddatetime: cannot process DELETE events");
65 
66  rel = trigdata->tg_relation;
67  relname = SPI_getrelname(rel);
68 
69  trigger = trigdata->tg_trigger;
70 
71  nargs = trigger->tgnargs;
72 
73  if (nargs != 1)
74  /* internal error */
75  elog(ERROR, "moddatetime (%s): A single argument was expected", relname);
76 
77  args = trigger->tgargs;
78  /* must be the field layout? */
79  tupdesc = rel->rd_att;
80 
81  /*
82  * This gets the position in the tuple of the field we want. args[0] being
83  * the name of the field to update, as passed in from the trigger.
84  */
85  attnum = SPI_fnumber(tupdesc, args[0]);
86 
87  /*
88  * This is where we check to see if the field we are supposed to update
89  * even exists.
90  */
91  if (attnum <= 0)
92  ereport(ERROR,
93  (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
94  errmsg("\"%s\" has no attribute \"%s\"",
95  relname, args[0])));
96 
97  /*
98  * Check the target field has an allowed type, and get the current
99  * datetime as a value of that type.
100  */
101  atttypid = SPI_gettypeid(tupdesc, attnum);
102  if (atttypid == TIMESTAMPOID)
104  CStringGetDatum("now"),
106  Int32GetDatum(-1));
107  else if (atttypid == TIMESTAMPTZOID)
109  CStringGetDatum("now"),
111  Int32GetDatum(-1));
112  else
113  {
114  ereport(ERROR,
115  (errcode(ERRCODE_TRIGGERED_ACTION_EXCEPTION),
116  errmsg("attribute \"%s\" of \"%s\" must be type TIMESTAMP or TIMESTAMPTZ",
117  args[0], relname)));
118  newdt = (Datum) 0; /* keep compiler quiet */
119  }
120  newdtnull = false;
121 
122  /* Replace the attnum'th column with newdt */
123  rettuple = heap_modify_tuple_by_cols(rettuple, tupdesc,
124  1, &attnum, &newdt, &newdtnull);
125 
126  /* Clean up */
127  pfree(relname);
128 
129  return PointerGetDatum(rettuple);
130 }
int SPI_fnumber(TupleDesc tupdesc, const char *fname)
Definition: spi.c:767
#define TIMESTAMPTZOID
Definition: pg_type.h:525
Oid SPI_gettypeid(TupleDesc tupdesc, int fnumber)
Definition: spi.c:900
PG_MODULE_MAGIC
Definition: moddatetime.c:25
#define PointerGetDatum(X)
Definition: postgres.h:562
int errcode(int sqlerrcode)
Definition: elog.c:575
PG_FUNCTION_INFO_V1(moddatetime)
unsigned int Oid
Definition: postgres_ext.h:31
void pfree(void *pointer)
Definition: mcxt.c:936
#define TIMESTAMPOID
Definition: pg_type.h:519
#define ObjectIdGetDatum(X)
Definition: postgres.h:513
#define ERROR
Definition: elog.h:43
#define CStringGetDatum(X)
Definition: postgres.h:584
#define ereport(elevel, rest)
Definition: elog.h:122
#define DirectFunctionCall3(func, arg1, arg2, arg3)
Definition: fmgr.h:589
uintptr_t Datum
Definition: postgres.h:372
Trigger * tg_trigger
Definition: trigger.h:37
HeapTuple tg_newtuple
Definition: trigger.h:36
char * SPI_getrelname(Relation rel)
Definition: spi.c:918
#define InvalidOid
Definition: postgres_ext.h:36
Datum timestamp_in(PG_FUNCTION_ARGS)
Definition: timestamp.c:143
#define CALLED_AS_TRIGGER(fcinfo)
Definition: trigger.h:25
TriggerEvent tg_event
Definition: trigger.h:33
HeapTuple heap_modify_tuple_by_cols(HeapTuple tuple, TupleDesc tupleDesc, int nCols, int *replCols, Datum *replValues, bool *replIsnull)
Definition: heaptuple.c:865
#define TRIGGER_FIRED_BEFORE(event)
Definition: trigger.h:134
#define Int32GetDatum(X)
Definition: postgres.h:485
#define TRIGGER_FIRED_BY_INSERT(event)
Definition: trigger.h:116
Datum timestamptz_in(PG_FUNCTION_ARGS)
Definition: timestamp.c:383
int errmsg(const char *fmt,...)
Definition: elog.c:797
int16 tgnargs
Definition: reltrigger.h:37
#define PG_FUNCTION_ARGS
Definition: fmgr.h:158
#define elog
Definition: elog.h:219
Datum moddatetime(PG_FUNCTION_ARGS)
Definition: moddatetime.c:30
#define TRIGGER_FIRED_FOR_ROW(event)
Definition: trigger.h:128
#define TRIGGER_FIRED_BY_UPDATE(event)
Definition: trigger.h:122
Relation tg_relation
Definition: trigger.h:34