PostgreSQL Source Code  git master
lo.c
Go to the documentation of this file.
1 /*
2  * PostgreSQL definitions for managed Large Objects.
3  *
4  * contrib/lo/lo.c
5  *
6  */
7 
8 #include "postgres.h"
9 
10 #include "commands/trigger.h"
11 #include "executor/spi.h"
12 #include "utils/builtins.h"
13 #include "utils/rel.h"
14 
16 
17 
18 /*
19  * This is the trigger that protects us from orphaned large objects
20  */
22 
23 Datum
25 {
26  TriggerData *trigdata = (TriggerData *) fcinfo->context;
27  int attnum; /* attribute number to monitor */
28  char **args; /* Args containing attr name */
29  TupleDesc tupdesc; /* Tuple Descriptor */
30  HeapTuple rettuple; /* Tuple to be returned */
31  bool isdelete; /* are we deleting? */
32  HeapTuple newtuple; /* The new value for tuple */
33  HeapTuple trigtuple; /* The original value of tuple */
34 
35  if (!CALLED_AS_TRIGGER(fcinfo)) /* internal error */
36  elog(ERROR, "lo_manage: not fired by trigger manager");
37 
38  if (!TRIGGER_FIRED_FOR_ROW(trigdata->tg_event)) /* internal error */
39  elog(ERROR, "%s: must be fired for row",
40  trigdata->tg_trigger->tgname);
41 
42  /*
43  * Fetch some values from trigdata
44  */
45  newtuple = trigdata->tg_newtuple;
46  trigtuple = trigdata->tg_trigtuple;
47  tupdesc = trigdata->tg_relation->rd_att;
48  args = trigdata->tg_trigger->tgargs;
49 
50  if (args == NULL) /* internal error */
51  elog(ERROR, "%s: no column name provided in the trigger definition",
52  trigdata->tg_trigger->tgname);
53 
54  /* tuple to return to Executor */
55  if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
56  rettuple = newtuple;
57  else
58  rettuple = trigtuple;
59 
60  /* Are we deleting the row? */
61  isdelete = TRIGGER_FIRED_BY_DELETE(trigdata->tg_event);
62 
63  /* Get the column we're interested in */
64  attnum = SPI_fnumber(tupdesc, args[0]);
65 
66  if (attnum <= 0)
67  elog(ERROR, "%s: column \"%s\" does not exist",
68  trigdata->tg_trigger->tgname, args[0]);
69 
70  /*
71  * Handle updates
72  *
73  * Here, if the value of the monitored attribute changes, then the large
74  * object associated with the original value is unlinked.
75  */
76  if (newtuple != NULL &&
78  {
79  char *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
80  char *newv = SPI_getvalue(newtuple, tupdesc, attnum);
81 
82  if (orig != NULL && (newv == NULL || strcmp(orig, newv) != 0))
84  ObjectIdGetDatum(atooid(orig)));
85 
86  if (newv)
87  pfree(newv);
88  if (orig)
89  pfree(orig);
90  }
91 
92  /*
93  * Handle deleting of rows
94  *
95  * Here, we unlink the large object associated with the managed attribute
96  */
97  if (isdelete)
98  {
99  char *orig = SPI_getvalue(trigtuple, tupdesc, attnum);
100 
101  if (orig != NULL)
102  {
104  ObjectIdGetDatum(atooid(orig)));
105 
106  pfree(orig);
107  }
108  }
109 
110  return PointerGetDatum(rettuple);
111 }
Datum be_lo_unlink(PG_FUNCTION_ARGS)
Definition: be-fsstubs.c:314
bool bms_is_member(int x, const Bitmapset *a)
Definition: bitmapset.c:510
#define ERROR
Definition: elog.h:39
#define elog(elevel,...)
Definition: elog.h:224
#define DirectFunctionCall1(func, arg1)
Definition: fmgr.h:642
#define PG_FUNCTION_ARGS
Definition: fmgr.h:193
if(TABLE==NULL||TABLE_index==NULL)
Definition: isn.c:77
PG_MODULE_MAGIC
Definition: lo.c:15
Datum lo_manage(PG_FUNCTION_ARGS)
Definition: lo.c:24
PG_FUNCTION_INFO_V1(lo_manage)
void pfree(void *pointer)
Definition: mcxt.c:1508
int16 attnum
Definition: pg_attribute.h:74
static Datum PointerGetDatum(const void *X)
Definition: postgres.h:322
uintptr_t Datum
Definition: postgres.h:64
static Datum ObjectIdGetDatum(Oid X)
Definition: postgres.h:252
#define atooid(x)
Definition: postgres_ext.h:42
int SPI_fnumber(TupleDesc tupdesc, const char *fname)
Definition: spi.c:1172
char * SPI_getvalue(HeapTuple tuple, TupleDesc tupdesc, int fnumber)
Definition: spi.c:1217
TupleDesc rd_att
Definition: rel.h:112
Relation tg_relation
Definition: trigger.h:35
const Bitmapset * tg_updatedcols
Definition: trigger.h:43
TriggerEvent tg_event
Definition: trigger.h:34
HeapTuple tg_newtuple
Definition: trigger.h:37
Trigger * tg_trigger
Definition: trigger.h:38
HeapTuple tg_trigtuple
Definition: trigger.h:36
char * tgname
Definition: reltrigger.h:27
char ** tgargs
Definition: reltrigger.h:41
#define FirstLowInvalidHeapAttributeNumber
Definition: sysattr.h:27
#define TRIGGER_FIRED_BY_DELETE(event)
Definition: trigger.h:113
#define CALLED_AS_TRIGGER(fcinfo)
Definition: trigger.h:26
#define TRIGGER_FIRED_FOR_ROW(event)
Definition: trigger.h:122
#define TRIGGER_FIRED_BY_UPDATE(event)
Definition: trigger.h:116