contrib/pgrowlocks/pgrowlocks.c

   1 /*
   2  * contrib/pgrowlocks/pgrowlocks.c
   3  *
   4  * Copyright (c) 2005-2006      Tatsuo Ishii
   5  *
   6  * Permission to use, copy, modify, and distribute this software and
   7  * its documentation for any purpose, without fee, and without a
   8  * written agreement is hereby granted, provided that the above
   9  * copyright notice and this paragraph and the following two
  10  * paragraphs appear in all copies.
  11  *
  12  * IN NO EVENT SHALL THE AUTHOR BE LIABLE TO ANY PARTY FOR DIRECT,
  13  * INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
  14  * LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
  15  * DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED
  16  * OF THE POSSIBILITY OF SUCH DAMAGE.
  17  *
  18  * THE AUTHOR SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT
  19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  20  * A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS
  21  * IS" BASIS, AND THE AUTHOR HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE,
  22  * SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  23  */
  24
  25 #include "postgres.h"
  26
  27 #include "access/heapam.h"
  28 #include "access/multixact.h"
  29 #include "access/relscan.h"
  30 #include "access/xact.h"
  31 #include "catalog/namespace.h"
  32 #include "funcapi.h"
  33 #include "miscadmin.h"
  34 #include "storage/bufmgr.h"
  35 #include "storage/procarray.h"
  36 #include "utils/acl.h"
  37 #include "utils/builtins.h"
  38 #include "utils/tqual.h"
  39
  40
  41 PG_MODULE_MAGIC;
  42
  43 PG_FUNCTION_INFO_V1(pgrowlocks);
  44
  45 extern Datum pgrowlocks(PG_FUNCTION_ARGS);
  46
  47 /* ----------
  48  * pgrowlocks:
  49  * returns tids of rows being locked
  50  * ----------
  51  */
  52
  53 #define NCHARS 32
  54
  55 typedef struct
  56 {
  57         Relation        rel;
  58         HeapScanDesc scan;
  59         int                     ncolumns;
  60 } MyData;
  61
  62 Datum
  63 pgrowlocks(PG_FUNCTION_ARGS)
  64 {
  65         FuncCallContext *funcctx;
  66         HeapScanDesc scan;
  67         HeapTuple       tuple;
  68         TupleDesc       tupdesc;
  69         AttInMetadata *attinmeta;
  70         Datum           result;
  71         MyData     *mydata;
  72         Relation        rel;
  73
  74         if (SRF_IS_FIRSTCALL())
  75         {
  76                 text       *relname;
  77                 RangeVar   *relrv;
  78                 MemoryContext oldcontext;
  79                 AclResult       aclresult;
  80
  81                 funcctx = SRF_FIRSTCALL_INIT();
  82                 oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
  83
  84                 /* Build a tuple descriptor for our result type */
  85                 if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
  86                         elog(ERROR, "return type must be a row type");
  87
  88                 attinmeta = TupleDescGetAttInMetadata(tupdesc);
  89                 funcctx->attinmeta = attinmeta;
  90
  91                 relname = PG_GETARG_TEXT_P(0);
  92                 relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
  93                 rel = heap_openrv(relrv, AccessShareLock);
  94
  95                 /* check permissions: must have SELECT on table */
  96                 aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
  97                                                                           ACL_SELECT);
  98                 if (aclresult != ACLCHECK_OK)
  99                         aclcheck_error(aclresult, ACL_KIND_CLASS,
 100                                                    RelationGetRelationName(rel));
 101
 102                 scan = heap_beginscan(rel, SnapshotNow, 0, NULL);
 103                 mydata = palloc(sizeof(*mydata));
 104                 mydata->rel = rel;
 105                 mydata->scan = scan;
 106                 mydata->ncolumns = tupdesc->natts;
 107                 funcctx->user_fctx = mydata;
 108
 109                 MemoryContextSwitchTo(oldcontext);
 110         }
 111
 112         funcctx = SRF_PERCALL_SETUP();
 113         attinmeta = funcctx->attinmeta;
 114         mydata = (MyData *) funcctx->user_fctx;
 115         scan = mydata->scan;
 116
 117         /* scan the relation */
 118         while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
 119         {
 120                 /* must hold a buffer lock to call HeapTupleSatisfiesUpdate */
 121                 LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
 122
 123                 if (HeapTupleSatisfiesUpdate(tuple->t_data,
 124                                                                          GetCurrentCommandId(false),
 125                                                                          scan->rs_cbuf) == HeapTupleBeingUpdated)
 126                 {
 127
 128                         char      **values;
 129                         int                     i;
 130
 131                         values = (char **) palloc(mydata->ncolumns * sizeof(char *));
 132
 133                         i = 0;
 134                         values[i++] = (char *) DirectFunctionCall1(tidout, PointerGetDatum(&tuple->t_self));
 135
 136                         if (tuple->t_data->t_infomask & HEAP_XMAX_SHARED_LOCK)
 137                                 values[i++] = pstrdup("Shared");
 138                         else
 139                                 values[i++] = pstrdup("Exclusive");
 140                         values[i] = palloc(NCHARS * sizeof(char));
 141                         snprintf(values[i++], NCHARS, "%d", HeapTupleHeaderGetXmax(tuple->t_data));
 142                         if (tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI)
 143                         {
 144                                 TransactionId *xids;
 145                                 int                     nxids;
 146                                 int                     j;
 147                                 int                     isValidXid = 0;         /* any valid xid ever exists? */
 148
 149                                 values[i++] = pstrdup("true");
 150                                 nxids = GetMultiXactIdMembers(HeapTupleHeaderGetXmax(tuple->t_data), &xids);
 151                                 if (nxids == -1)
 152                                 {
 153                                         elog(ERROR, "GetMultiXactIdMembers returns error");
 154                                 }
 155
 156                                 values[i] = palloc(NCHARS * nxids);
 157                                 values[i + 1] = palloc(NCHARS * nxids);
 158                                 strcpy(values[i], "{");
 159                                 strcpy(values[i + 1], "{");
 160
 161                                 for (j = 0; j < nxids; j++)
 162                                 {
 163                                         char            buf[NCHARS];
 164
 165                                         if (TransactionIdIsInProgress(xids[j]))
 166                                         {
 167                                                 if (isValidXid)
 168                                                 {
 169                                                         strcat(values[i], ",");
 170                                                         strcat(values[i + 1], ",");
 171                                                 }
 172                                                 snprintf(buf, NCHARS, "%d", xids[j]);
 173                                                 strcat(values[i], buf);
 174                                                 snprintf(buf, NCHARS, "%d", BackendXidGetPid(xids[j]));
 175                                                 strcat(values[i + 1], buf);
 176
 177                                                 isValidXid = 1;
 178                                         }
 179                                 }
 180
 181                                 strcat(values[i], "}");
 182                                 strcat(values[i + 1], "}");
 183                                 i++;
 184                         }
 185                         else
 186                         {
 187                                 values[i++] = pstrdup("false");
 188                                 values[i] = palloc(NCHARS * sizeof(char));
 189                                 snprintf(values[i++], NCHARS, "{%d}", HeapTupleHeaderGetXmax(tuple->t_data));
 190
 191                                 values[i] = palloc(NCHARS * sizeof(char));
 192                                 snprintf(values[i++], NCHARS, "{%d}", BackendXidGetPid(HeapTupleHeaderGetXmax(tuple->t_data)));
 193                         }
 194
 195                         LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
 196
 197                         /* build a tuple */
 198                         tuple = BuildTupleFromCStrings(attinmeta, values);
 199
 200                         /* make the tuple into a datum */
 201                         result = HeapTupleGetDatum(tuple);
 202
 203                         /* Clean up */
 204                         for (i = 0; i < mydata->ncolumns; i++)
 205                                 pfree(values[i]);
 206                         pfree(values);
 207
 208                         SRF_RETURN_NEXT(funcctx, result);
 209                 }
 210                 else
 211                 {
 212                         LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
 213                 }
 214         }
 215
 216         heap_endscan(scan);
 217         heap_close(mydata->rel, AccessShareLock);
 218
 219         SRF_RETURN_DONE(funcctx);
 220 }