granicus.if.org Git - postgresql/blob - src/backend/access/common/indextuple.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * indextuple.c
   4  *         This file contains index tuple accessor and mutator routines,
   5  *         as well as various tuple utilities.
   6  *
   7  * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  *
  11  * IDENTIFICATION
  12  *        src/backend/access/common/indextuple.c
  13  *
  14  *-------------------------------------------------------------------------
  15  */
  16
  17 #include "postgres.h"
  18
  19 #include "access/heapam.h"
  20 #include "access/itup.h"
  21 #include "access/tuptoaster.h"
  22
  23
  24 /* ----------------------------------------------------------------
  25  *                                index_ tuple interface routines
  26  * ----------------------------------------------------------------
  27  */
  28
  29 /* ----------------
  30  *              index_form_tuple
  31  * ----------------
  32  */
  33 IndexTuple
  34 index_form_tuple(TupleDesc tupleDescriptor,
  35                                  Datum *values,
  36                                  bool *isnull)
  37 {
  38         char       *tp;                         /* tuple pointer */
  39         IndexTuple      tuple;                  /* return tuple */
  40         Size            size,
  41                                 data_size,
  42                                 hoff;
  43         int                     i;
  44         unsigned short infomask = 0;
  45         bool            hasnull = false;
  46         uint16          tupmask = 0;
  47         int                     numberOfAttributes = tupleDescriptor->natts;
  48
  49 #ifdef TOAST_INDEX_HACK
  50         Datum           untoasted_values[INDEX_MAX_KEYS];
  51         bool            untoasted_free[INDEX_MAX_KEYS];
  52 #endif
  53
  54         if (numberOfAttributes > INDEX_MAX_KEYS)
  55                 ereport(ERROR,
  56                                 (errcode(ERRCODE_TOO_MANY_COLUMNS),
  57                                  errmsg("number of index columns (%d) exceeds limit (%d)",
  58                                                 numberOfAttributes, INDEX_MAX_KEYS)));
  59
  60 #ifdef TOAST_INDEX_HACK
  61         for (i = 0; i < numberOfAttributes; i++)
  62         {
  63                 Form_pg_attribute att = tupleDescriptor->attrs[i];
  64
  65                 untoasted_values[i] = values[i];
  66                 untoasted_free[i] = false;
  67
  68                 /* Do nothing if value is NULL or not of varlena type */
  69                 if (isnull[i] || att->attlen != -1)
  70                         continue;
  71
  72                 /*
  73                  * If value is stored EXTERNAL, must fetch it so we are not depending
  74                  * on outside storage.  This should be improved someday.
  75                  */
  76                 if (VARATT_IS_EXTERNAL(DatumGetPointer(values[i])))
  77                 {
  78                         untoasted_values[i] =
  79                                 PointerGetDatum(heap_tuple_fetch_attr((struct varlena *)
  80                                                                                                 DatumGetPointer(values[i])));
  81                         untoasted_free[i] = true;
  82                 }
  83
  84                 /*
  85                  * If value is above size target, and is of a compressible datatype,
  86                  * try to compress it in-line.
  87                  */
  88                 if (!VARATT_IS_EXTENDED(DatumGetPointer(untoasted_values[i])) &&
  89                 VARSIZE(DatumGetPointer(untoasted_values[i])) > TOAST_INDEX_TARGET &&
  90                         (att->attstorage == 'x' || att->attstorage == 'm'))
  91                 {
  92                         Datum           cvalue = toast_compress_datum(untoasted_values[i]);
  93
  94                         if (DatumGetPointer(cvalue) != NULL)
  95                         {
  96                                 /* successful compression */
  97                                 if (untoasted_free[i])
  98                                         pfree(DatumGetPointer(untoasted_values[i]));
  99                                 untoasted_values[i] = cvalue;
 100                                 untoasted_free[i] = true;
 101                         }
 102                 }
 103         }
 104 #endif
 105
 106         for (i = 0; i < numberOfAttributes; i++)
 107         {
 108                 if (isnull[i])
 109                 {
 110                         hasnull = true;
 111                         break;
 112                 }
 113         }
 114
 115         if (hasnull)
 116                 infomask |= INDEX_NULL_MASK;
 117
 118         hoff = IndexInfoFindDataOffset(infomask);
 119 #ifdef TOAST_INDEX_HACK
 120         data_size = heap_compute_data_size(tupleDescriptor,
 121                                                                            untoasted_values, isnull);
 122 #else
 123         data_size = heap_compute_data_size(tupleDescriptor,
 124                                                                            values, isnull);
 125 #endif
 126         size = hoff + data_size;
 127         size = MAXALIGN(size);          /* be conservative */
 128
 129         tp = (char *) palloc0(size);
 130         tuple = (IndexTuple) tp;
 131
 132         heap_fill_tuple(tupleDescriptor,
 133 #ifdef TOAST_INDEX_HACK
 134                                         untoasted_values,
 135 #else
 136                                         values,
 137 #endif
 138                                         isnull,
 139                                         (char *) tp + hoff,
 140                                         data_size,
 141                                         &tupmask,
 142                                         (hasnull ? (bits8 *) tp + sizeof(IndexTupleData) : NULL));
 143
 144 #ifdef TOAST_INDEX_HACK
 145         for (i = 0; i < numberOfAttributes; i++)
 146         {
 147                 if (untoasted_free[i])
 148                         pfree(DatumGetPointer(untoasted_values[i]));
 149         }
 150 #endif
 151
 152         /*
 153          * We do this because heap_fill_tuple wants to initialize a "tupmask"
 154          * which is used for HeapTuples, but we want an indextuple infomask. The
 155          * only relevant info is the "has variable attributes" field. We have
 156          * already set the hasnull bit above.
 157          */
 158         if (tupmask & HEAP_HASVARWIDTH)
 159                 infomask |= INDEX_VAR_MASK;
 160
 161         /*
 162          * Here we make sure that the size will fit in the field reserved for it
 163          * in t_info.
 164          */
 165         if ((size & INDEX_SIZE_MASK) != size)
 166                 ereport(ERROR,
 167                                 (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
 168                                  errmsg("index row requires %lu bytes, maximum size is %lu",
 169                                                 (unsigned long) size,
 170                                                 (unsigned long) INDEX_SIZE_MASK)));
 171
 172         infomask |= size;
 173
 174         /*
 175          * initialize metadata
 176          */
 177         tuple->t_info = infomask;
 178         return tuple;
 179 }
 180
 181 /* ----------------
 182  *              nocache_index_getattr
 183  *
 184  *              This gets called from index_getattr() macro, and only in cases
 185  *              where we can't use cacheoffset and the value is not null.
 186  *
 187  *              This caches attribute offsets in the attribute descriptor.
 188  *
 189  *              An alternative way to speed things up would be to cache offsets
 190  *              with the tuple, but that seems more difficult unless you take
 191  *              the storage hit of actually putting those offsets into the
 192  *              tuple you send to disk.  Yuck.
 193  *
 194  *              This scheme will be slightly slower than that, but should
 195  *              perform well for queries which hit large #'s of tuples.  After
 196  *              you cache the offsets once, examining all the other tuples using
 197  *              the same attribute descriptor will go much quicker. -cim 5/4/91
 198  * ----------------
 199  */
 200 Datum
 201 nocache_index_getattr(IndexTuple tup,
 202                                           int attnum,
 203                                           TupleDesc tupleDesc)
 204 {
 205         Form_pg_attribute *att = tupleDesc->attrs;
 206         char       *tp;                         /* ptr to data part of tuple */
 207         bits8      *bp = NULL;          /* ptr to null bitmap in tuple */
 208         bool            slow = false;   /* do we have to walk attrs? */
 209         int                     data_off;               /* tuple data offset */
 210         int                     off;                    /* current offset within data */
 211
 212         /* ----------------
 213          *       Three cases:
 214          *
 215          *       1: No nulls and no variable-width attributes.
 216          *       2: Has a null or a var-width AFTER att.
 217          *       3: Has nulls or var-widths BEFORE att.
 218          * ----------------
 219          */
 220
 221         data_off = IndexInfoFindDataOffset(tup->t_info);
 222
 223         attnum--;
 224
 225         if (IndexTupleHasNulls(tup))
 226         {
 227                 /*
 228                  * there's a null somewhere in the tuple
 229                  *
 230                  * check to see if desired att is null
 231                  */
 232
 233                 /* XXX "knows" t_bits are just after fixed tuple header! */
 234                 bp = (bits8 *) ((char *) tup + sizeof(IndexTupleData));
 235
 236                 /*
 237                  * Now check to see if any preceding bits are null...
 238                  */
 239                 {
 240                         int                     byte = attnum >> 3;
 241                         int                     finalbit = attnum & 0x07;
 242
 243                         /* check for nulls "before" final bit of last byte */
 244                         if ((~bp[byte]) & ((1 << finalbit) - 1))
 245                                 slow = true;
 246                         else
 247                         {
 248                                 /* check for nulls in any "earlier" bytes */
 249                                 int                     i;
 250
 251                                 for (i = 0; i < byte; i++)
 252                                 {
 253                                         if (bp[i] != 0xFF)
 254                                         {
 255                                                 slow = true;
 256                                                 break;
 257                                         }
 258                                 }
 259                         }
 260                 }
 261         }
 262
 263         tp = (char *) tup + data_off;
 264
 265         if (!slow)
 266         {
 267                 /*
 268                  * If we get here, there are no nulls up to and including the target
 269                  * attribute.  If we have a cached offset, we can use it.
 270                  */
 271                 if (att[attnum]->attcacheoff >= 0)
 272                 {
 273                         return fetchatt(att[attnum],
 274                                                         tp + att[attnum]->attcacheoff);
 275                 }
 276
 277                 /*
 278                  * Otherwise, check for non-fixed-length attrs up to and including
 279                  * target.      If there aren't any, it's safe to cheaply initialize the
 280                  * cached offsets for these attrs.
 281                  */
 282                 if (IndexTupleHasVarwidths(tup))
 283                 {
 284                         int                     j;
 285
 286                         for (j = 0; j <= attnum; j++)
 287                         {
 288                                 if (att[j]->attlen <= 0)
 289                                 {
 290                                         slow = true;
 291                                         break;
 292                                 }
 293                         }
 294                 }
 295         }
 296
 297         if (!slow)
 298         {
 299                 int                     natts = tupleDesc->natts;
 300                 int                     j = 1;
 301
 302                 /*
 303                  * If we get here, we have a tuple with no nulls or var-widths up to
 304                  * and including the target attribute, so we can use the cached offset
 305                  * ... only we don't have it yet, or we'd not have got here.  Since
 306                  * it's cheap to compute offsets for fixed-width columns, we take the
 307                  * opportunity to initialize the cached offsets for *all* the leading
 308                  * fixed-width columns, in hope of avoiding future visits to this
 309                  * routine.
 310                  */
 311                 att[0]->attcacheoff = 0;
 312
 313                 /* we might have set some offsets in the slow path previously */
 314                 while (j < natts && att[j]->attcacheoff > 0)
 315                         j++;
 316
 317                 off = att[j - 1]->attcacheoff + att[j - 1]->attlen;
 318
 319                 for (; j < natts; j++)
 320                 {
 321                         if (att[j]->attlen <= 0)
 322                                 break;
 323
 324                         off = att_align_nominal(off, att[j]->attalign);
 325
 326                         att[j]->attcacheoff = off;
 327
 328                         off += att[j]->attlen;
 329                 }
 330
 331                 Assert(j > attnum);
 332
 333                 off = att[attnum]->attcacheoff;
 334         }
 335         else
 336         {
 337                 bool            usecache = true;
 338                 int                     i;
 339
 340                 /*
 341                  * Now we know that we have to walk the tuple CAREFULLY.  But we still
 342                  * might be able to cache some offsets for next time.
 343                  *
 344                  * Note - This loop is a little tricky.  For each non-null attribute,
 345                  * we have to first account for alignment padding before the attr,
 346                  * then advance over the attr based on its length.      Nulls have no
 347                  * storage and no alignment padding either.  We can use/set
 348                  * attcacheoff until we reach either a null or a var-width attribute.
 349                  */
 350                 off = 0;
 351                 for (i = 0;; i++)               /* loop exit is at "break" */
 352                 {
 353                         if (IndexTupleHasNulls(tup) && att_isnull(i, bp))
 354                         {
 355                                 usecache = false;
 356                                 continue;               /* this cannot be the target att */
 357                         }
 358
 359                         /* If we know the next offset, we can skip the rest */
 360                         if (usecache && att[i]->attcacheoff >= 0)
 361                                 off = att[i]->attcacheoff;
 362                         else if (att[i]->attlen == -1)
 363                         {
 364                                 /*
 365                                  * We can only cache the offset for a varlena attribute if the
 366                                  * offset is already suitably aligned, so that there would be
 367                                  * no pad bytes in any case: then the offset will be valid for
 368                                  * either an aligned or unaligned value.
 369                                  */
 370                                 if (usecache &&
 371                                         off == att_align_nominal(off, att[i]->attalign))
 372                                         att[i]->attcacheoff = off;
 373                                 else
 374                                 {
 375                                         off = att_align_pointer(off, att[i]->attalign, -1,
 376                                                                                         tp + off);
 377                                         usecache = false;
 378                                 }
 379                         }
 380                         else
 381                         {
 382                                 /* not varlena, so safe to use att_align_nominal */
 383                                 off = att_align_nominal(off, att[i]->attalign);
 384
 385                                 if (usecache)
 386                                         att[i]->attcacheoff = off;
 387                         }
 388
 389                         if (i == attnum)
 390                                 break;
 391
 392                         off = att_addlength_pointer(off, att[i]->attlen, tp + off);
 393
 394                         if (usecache && att[i]->attlen <= 0)
 395                                 usecache = false;
 396                 }
 397         }
 398
 399         return fetchatt(att[attnum], tp + off);
 400 }
 401
 402 /*
 403  * Convert an index tuple into Datum/isnull arrays.
 404  *
 405  * The caller must allocate sufficient storage for the output arrays.
 406  * (INDEX_MAX_KEYS entries should be enough.)
 407  */
 408 void
 409 index_deform_tuple(IndexTuple tup, TupleDesc tupleDescriptor,
 410                                    Datum *values, bool *isnull)
 411 {
 412         int                     i;
 413
 414         /* Assert to protect callers who allocate fixed-size arrays */
 415         Assert(tupleDescriptor->natts <= INDEX_MAX_KEYS);
 416
 417         for (i = 0; i < tupleDescriptor->natts; i++)
 418         {
 419                 values[i] = index_getattr(tup, i + 1, tupleDescriptor, &isnull[i]);
 420         }
 421 }
 422
 423 /*
 424  * Create a palloc'd copy of an index tuple.
 425  */
 426 IndexTuple
 427 CopyIndexTuple(IndexTuple source)
 428 {
 429         IndexTuple      result;
 430         Size            size;
 431
 432         size = IndexTupleSize(source);
 433         result = (IndexTuple) palloc(size);
 434         memcpy(result, source, size);
 435         return result;
 436 }