granicus.if.org Git - postgresql/blob - src/backend/executor/nodeAppend.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * nodeAppend.c
   4  *        routines to handle append nodes.
   5  *
   6  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  *
  10  * IDENTIFICATION
  11  *        $Header: /cvsroot/pgsql/src/backend/executor/nodeAppend.c,v 1.43 2001/10/25 05:49:28 momjian Exp $
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 /* INTERFACE ROUTINES
  16  *              ExecInitAppend  - initialize the append node
  17  *              ExecProcAppend  - retrieve the next tuple from the node
  18  *              ExecEndAppend   - shut down the append node
  19  *              ExecReScanAppend - rescan the append node
  20  *
  21  *       NOTES
  22  *              Each append node contains a list of one or more subplans which
  23  *              must be iteratively processed (forwards or backwards).
  24  *              Tuples are retrieved by executing the 'whichplan'th subplan
  25  *              until the subplan stops returning tuples, at which point that
  26  *              plan is shut down and the next started up.
  27  *
  28  *              Append nodes don't make use of their left and right
  29  *              subtrees, rather they maintain a list of subplans so
  30  *              a typical append node looks like this in the plan tree:
  31  *
  32  *                                 ...
  33  *                                 /
  34  *                              Append -------+------+------+--- nil
  35  *                              /       \                 |              |              |
  36  *                        nil   nil              ...    ...    ...
  37  *                                                               subplans
  38  *
  39  *              Append nodes are currently used for unions, and to support
  40  *              inheritance queries, where several relations need to be scanned.
  41  *              For example, in our standard person/student/employee/student-emp
  42  *              example, where student and employee inherit from person
  43  *              and student-emp inherits from student and employee, the
  44  *              query:
  45  *
  46  *                              retrieve (e.name) from e in person*
  47  *
  48  *              generates the plan:
  49  *
  50  *                                |
  51  *                              Append -------+-------+--------+--------+
  52  *                              /       \                 |               |                |            |
  53  *                        nil   nil              Scan    Scan     Scan     Scan
  54  *                                                        |               |                |            |
  55  *                                                      person employee student student-emp
  56  */
  57
  58 #include "postgres.h"
  59
  60 #include "access/heapam.h"
  61 #include "executor/execdebug.h"
  62 #include "executor/nodeAppend.h"
  63 #include "parser/parsetree.h"
  64
  65 static bool exec_append_initialize_next(Append *node);
  66
  67
  68 /* ----------------------------------------------------------------
  69  *              exec_append_initialize_next
  70  *
  71  *              Sets up the append node state (i.e. the append state node)
  72  *              for the "next" scan.
  73  *
  74  *              Returns t iff there is a "next" scan to process.
  75  * ----------------------------------------------------------------
  76  */
  77 static bool
  78 exec_append_initialize_next(Append *node)
  79 {
  80         EState     *estate;
  81         AppendState *appendstate;
  82         int                     whichplan;
  83
  84         /*
  85          * get information from the append node
  86          */
  87         estate = node->plan.state;
  88         appendstate = node->appendstate;
  89         whichplan = appendstate->as_whichplan;
  90
  91         if (whichplan < appendstate->as_firstplan)
  92         {
  93                 /*
  94                  * if scanning in reverse, we start at the last scan in the list
  95                  * and then proceed back to the first.. in any case we inform
  96                  * ExecProcAppend that we are at the end of the line by returning
  97                  * FALSE
  98                  */
  99                 appendstate->as_whichplan = appendstate->as_firstplan;
 100                 return FALSE;
 101         }
 102         else if (whichplan > appendstate->as_lastplan)
 103         {
 104                 /*
 105                  * as above, end the scan if we go beyond the last scan in our
 106                  * list..
 107                  */
 108                 appendstate->as_whichplan = appendstate->as_lastplan;
 109                 return FALSE;
 110         }
 111         else
 112         {
 113                 /*
 114                  * initialize the scan
 115                  *
 116                  * If we are controlling the target relation, select the proper
 117                  * active ResultRelInfo and junk filter for this target.
 118                  */
 119                 if (node->isTarget)
 120                 {
 121                         Assert(whichplan < estate->es_num_result_relations);
 122                         estate->es_result_relation_info =
 123                                 estate->es_result_relations + whichplan;
 124                         estate->es_junkFilter =
 125                                 estate->es_result_relation_info->ri_junkFilter;
 126                 }
 127
 128                 return TRUE;
 129         }
 130 }
 131
 132 /* ----------------------------------------------------------------
 133  *              ExecInitAppend
 134  *
 135  *              Begins all of the subscans of the append node, storing the
 136  *              scan structures in the 'initialized' vector of the append-state
 137  *              structure.
 138  *
 139  *         (This is potentially wasteful, since the entire result of the
 140  *              append node may not be scanned, but this way all of the
 141  *              structures get allocated in the executor's top level memory
 142  *              block instead of that of the call to ExecProcAppend.)
 143  *
 144  *              Special case: during an EvalPlanQual recheck query of an inherited
 145  *              target relation, we only want to initialize and scan the single
 146  *              subplan that corresponds to the target relation being checked.
 147  * ----------------------------------------------------------------
 148  */
 149 bool
 150 ExecInitAppend(Append *node, EState *estate, Plan *parent)
 151 {
 152         AppendState *appendstate;
 153         int                     nplans;
 154         List       *appendplans;
 155         bool       *initialized;
 156         int                     i;
 157         Plan       *initNode;
 158
 159         CXT1_printf("ExecInitAppend: context is %d\n", CurrentMemoryContext);
 160
 161         /*
 162          * assign execution state to node and get information for append state
 163          */
 164         node->plan.state = estate;
 165
 166         appendplans = node->appendplans;
 167         nplans = length(appendplans);
 168
 169         initialized = (bool *) palloc(nplans * sizeof(bool));
 170         MemSet(initialized, 0, nplans * sizeof(bool));
 171
 172         /*
 173          * create new AppendState for our append node
 174          */
 175         appendstate = makeNode(AppendState);
 176         appendstate->as_nplans = nplans;
 177         appendstate->as_initialized = initialized;
 178
 179         node->appendstate = appendstate;
 180
 181         /*
 182          * Do we want to scan just one subplan?  (Special case for
 183          * EvalPlanQual) XXX pretty dirty way of determining that this case
 184          * applies ...
 185          */
 186         if (node->isTarget && estate->es_evTuple != NULL)
 187         {
 188                 int                     tplan;
 189
 190                 tplan = estate->es_result_relation_info - estate->es_result_relations;
 191                 Assert(tplan >= 0 && tplan < nplans);
 192
 193                 appendstate->as_firstplan = tplan;
 194                 appendstate->as_lastplan = tplan;
 195         }
 196         else
 197         {
 198                 /* normal case, scan all subplans */
 199                 appendstate->as_firstplan = 0;
 200                 appendstate->as_lastplan = nplans - 1;
 201         }
 202
 203         /*
 204          * Miscellaneous initialization
 205          *
 206          * Append plans don't have expression contexts because they never call
 207          * ExecQual or ExecProject.
 208          */
 209
 210 #define APPEND_NSLOTS 1
 211
 212         /*
 213          * append nodes still have Result slots, which hold pointers to
 214          * tuples, so we have to initialize them.
 215          */
 216         ExecInitResultTupleSlot(estate, &appendstate->cstate);
 217
 218         /*
 219          * call ExecInitNode on each of the plans to be executed and save the
 220          * results into the array "initialized"
 221          */
 222         for (i = appendstate->as_firstplan; i <= appendstate->as_lastplan; i++)
 223         {
 224                 appendstate->as_whichplan = i;
 225                 exec_append_initialize_next(node);
 226
 227                 initNode = (Plan *) nth(i, appendplans);
 228                 initialized[i] = ExecInitNode(initNode, estate, (Plan *) node);
 229         }
 230
 231         /*
 232          * initialize tuple type
 233          */
 234         ExecAssignResultTypeFromTL((Plan *) node, &appendstate->cstate);
 235         appendstate->cstate.cs_ProjInfo = NULL;
 236
 237         /*
 238          * return the result from the first subplan's initialization
 239          */
 240         appendstate->as_whichplan = appendstate->as_firstplan;
 241         exec_append_initialize_next(node);
 242
 243         return TRUE;
 244 }
 245
 246 int
 247 ExecCountSlotsAppend(Append *node)
 248 {
 249         List       *plan;
 250         int                     nSlots = 0;
 251
 252         foreach(plan, node->appendplans)
 253                 nSlots += ExecCountSlotsNode((Plan *) lfirst(plan));
 254         return nSlots + APPEND_NSLOTS;
 255 }
 256
 257 /* ----------------------------------------------------------------
 258  *         ExecProcAppend
 259  *
 260  *              Handles the iteration over the multiple scans.
 261  *
 262  *         NOTE: Can't call this ExecAppend, that name is used in execMain.
 263  * ----------------------------------------------------------------
 264  */
 265 TupleTableSlot *
 266 ExecProcAppend(Append *node)
 267 {
 268         EState     *estate;
 269         AppendState *appendstate;
 270         int                     whichplan;
 271         List       *appendplans;
 272         Plan       *subnode;
 273         TupleTableSlot *result;
 274         TupleTableSlot *result_slot;
 275         ScanDirection direction;
 276
 277         /*
 278          * get information from the node
 279          */
 280         appendstate = node->appendstate;
 281         estate = node->plan.state;
 282         direction = estate->es_direction;
 283         appendplans = node->appendplans;
 284         whichplan = appendstate->as_whichplan;
 285         result_slot = appendstate->cstate.cs_ResultTupleSlot;
 286
 287         /*
 288          * figure out which subplan we are currently processing
 289          */
 290         subnode = (Plan *) nth(whichplan, appendplans);
 291
 292         if (subnode == NULL)
 293                 elog(DEBUG, "ExecProcAppend: subnode is NULL");
 294
 295         /*
 296          * get a tuple from the subplan
 297          */
 298         result = ExecProcNode(subnode, (Plan *) node);
 299
 300         if (!TupIsNull(result))
 301         {
 302                 /*
 303                  * if the subplan gave us something then place a copy of whatever
 304                  * we get into our result slot and return it.
 305                  *
 306                  * Note we rely on the subplan to retain ownership of the tuple for
 307                  * as long as we need it --- we don't copy it.
 308                  */
 309                 return ExecStoreTuple(result->val, result_slot, InvalidBuffer, false);
 310         }
 311         else
 312         {
 313                 /*
 314                  * .. go on to the "next" subplan in the appropriate direction and
 315                  * try processing again (recursively)
 316                  */
 317                 if (ScanDirectionIsForward(direction))
 318                         appendstate->as_whichplan++;
 319                 else
 320                         appendstate->as_whichplan--;
 321
 322                 /*
 323                  * return something from next node or an empty slot if all of our
 324                  * subplans have been exhausted.
 325                  */
 326                 if (exec_append_initialize_next(node))
 327                 {
 328                         ExecSetSlotDescriptorIsNew(result_slot, true);
 329                         return ExecProcAppend(node);
 330                 }
 331                 else
 332                         return ExecClearTuple(result_slot);
 333         }
 334 }
 335
 336 /* ----------------------------------------------------------------
 337  *              ExecEndAppend
 338  *
 339  *              Shuts down the subscans of the append node.
 340  *
 341  *              Returns nothing of interest.
 342  * ----------------------------------------------------------------
 343  */
 344 void
 345 ExecEndAppend(Append *node)
 346 {
 347         EState     *estate;
 348         AppendState *appendstate;
 349         int                     nplans;
 350         List       *appendplans;
 351         bool       *initialized;
 352         int                     i;
 353
 354         /*
 355          * get information from the node
 356          */
 357         appendstate = node->appendstate;
 358         estate = node->plan.state;
 359         appendplans = node->appendplans;
 360         nplans = appendstate->as_nplans;
 361         initialized = appendstate->as_initialized;
 362
 363         /*
 364          * shut down each of the subscans
 365          */
 366         for (i = 0; i < nplans; i++)
 367         {
 368                 if (initialized[i])
 369                         ExecEndNode((Plan *) nth(i, appendplans), (Plan *) node);
 370         }
 371 }
 372
 373 void
 374 ExecReScanAppend(Append *node, ExprContext *exprCtxt, Plan *parent)
 375 {
 376         AppendState *appendstate = node->appendstate;
 377         int                     i;
 378
 379         for (i = appendstate->as_firstplan; i <= appendstate->as_lastplan; i++)
 380         {
 381                 Plan       *subnode;
 382
 383                 subnode = (Plan *) nth(i, node->appendplans);
 384
 385                 /*
 386                  * ExecReScan doesn't know about my subplans, so I have to do
 387                  * changed-parameter signaling myself.
 388                  */
 389                 if (node->plan.chgParam != NULL)
 390                         SetChangedParamList(subnode, node->plan.chgParam);
 391
 392                 /*
 393                  * if chgParam of subnode is not null then plan will be re-scanned
 394                  * by first ExecProcNode.
 395                  */
 396                 if (subnode->chgParam == NULL)
 397                 {
 398                         /* make sure estate is correct for this subnode (needed??) */
 399                         appendstate->as_whichplan = i;
 400                         exec_append_initialize_next(node);
 401                         ExecReScan(subnode, exprCtxt, (Plan *) node);
 402                 }
 403         }
 404         appendstate->as_whichplan = appendstate->as_firstplan;
 405         exec_append_initialize_next(node);
 406 }