granicus.if.org Git - postgresql/blob - contrib/file_fdw/file_fdw.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * file_fdw.c
   4  *                foreign-data wrapper for server-side flat files.
   5  *
   6  * Copyright (c) 2010-2014, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *                contrib/file_fdw/file_fdw.c
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #include "postgres.h"
  14
  15 #include <sys/stat.h>
  16 #include <unistd.h>
  17
  18 #include "access/htup_details.h"
  19 #include "access/reloptions.h"
  20 #include "access/sysattr.h"
  21 #include "catalog/pg_foreign_table.h"
  22 #include "commands/copy.h"
  23 #include "commands/defrem.h"
  24 #include "commands/explain.h"
  25 #include "commands/vacuum.h"
  26 #include "foreign/fdwapi.h"
  27 #include "foreign/foreign.h"
  28 #include "miscadmin.h"
  29 #include "nodes/makefuncs.h"
  30 #include "optimizer/cost.h"
  31 #include "optimizer/pathnode.h"
  32 #include "optimizer/planmain.h"
  33 #include "optimizer/restrictinfo.h"
  34 #include "optimizer/var.h"
  35 #include "utils/memutils.h"
  36 #include "utils/rel.h"
  37
  38 PG_MODULE_MAGIC;
  39
  40 /*
  41  * Describes the valid options for objects that use this wrapper.
  42  */
  43 struct FileFdwOption
  44 {
  45         const char *optname;
  46         Oid                     optcontext;             /* Oid of catalog in which option may appear */
  47 };
  48
  49 /*
  50  * Valid options for file_fdw.
  51  * These options are based on the options for the COPY FROM command.
  52  * But note that force_not_null and force_null are handled as boolean options
  53  * attached to a column, not as table options.
  54  *
  55  * Note: If you are adding new option for user mapping, you need to modify
  56  * fileGetOptions(), which currently doesn't bother to look at user mappings.
  57  */
  58 static const struct FileFdwOption valid_options[] = {
  59         /* File options */
  60         {"filename", ForeignTableRelationId},
  61
  62         /* Format options */
  63         /* oids option is not supported */
  64         {"format", ForeignTableRelationId},
  65         {"header", ForeignTableRelationId},
  66         {"delimiter", ForeignTableRelationId},
  67         {"quote", ForeignTableRelationId},
  68         {"escape", ForeignTableRelationId},
  69         {"null", ForeignTableRelationId},
  70         {"encoding", ForeignTableRelationId},
  71         {"force_not_null", AttributeRelationId},
  72         {"force_null", AttributeRelationId},
  73         /*
  74          * force_quote is not supported by file_fdw because it's for COPY TO.
  75          */
  76
  77         /* Sentinel */
  78         {NULL, InvalidOid}
  79 };
  80
  81 /*
  82  * FDW-specific information for RelOptInfo.fdw_private.
  83  */
  84 typedef struct FileFdwPlanState
  85 {
  86         char       *filename;           /* file to read */
  87         List       *options;            /* merged COPY options, excluding filename */
  88         BlockNumber pages;                      /* estimate of file's physical size */
  89         double          ntuples;                /* estimate of number of rows in file */
  90 } FileFdwPlanState;
  91
  92 /*
  93  * FDW-specific information for ForeignScanState.fdw_state.
  94  */
  95 typedef struct FileFdwExecutionState
  96 {
  97         char       *filename;           /* file to read */
  98         List       *options;            /* merged COPY options, excluding filename */
  99         CopyState       cstate;                 /* state of reading file */
 100 } FileFdwExecutionState;
 101
 102 /*
 103  * SQL functions
 104  */
 105 PG_FUNCTION_INFO_V1(file_fdw_handler);
 106 PG_FUNCTION_INFO_V1(file_fdw_validator);
 107
 108 /*
 109  * FDW callback routines
 110  */
 111 static void fileGetForeignRelSize(PlannerInfo *root,
 112                                           RelOptInfo *baserel,
 113                                           Oid foreigntableid);
 114 static void fileGetForeignPaths(PlannerInfo *root,
 115                                         RelOptInfo *baserel,
 116                                         Oid foreigntableid);
 117 static ForeignScan *fileGetForeignPlan(PlannerInfo *root,
 118                                    RelOptInfo *baserel,
 119                                    Oid foreigntableid,
 120                                    ForeignPath *best_path,
 121                                    List *tlist,
 122                                    List *scan_clauses);
 123 static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
 124 static void fileBeginForeignScan(ForeignScanState *node, int eflags);
 125 static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
 126 static void fileReScanForeignScan(ForeignScanState *node);
 127 static void fileEndForeignScan(ForeignScanState *node);
 128 static bool fileAnalyzeForeignTable(Relation relation,
 129                                                 AcquireSampleRowsFunc *func,
 130                                                 BlockNumber *totalpages);
 131
 132 /*
 133  * Helper functions
 134  */
 135 static bool is_valid_option(const char *option, Oid context);
 136 static void fileGetOptions(Oid foreigntableid,
 137                            char **filename, List **other_options);
 138 static List *get_file_fdw_attribute_options(Oid relid);
 139 static bool check_selective_binary_conversion(RelOptInfo *baserel,
 140                                                                   Oid foreigntableid,
 141                                                                   List **columns);
 142 static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 143                           FileFdwPlanState *fdw_private);
 144 static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 145                            FileFdwPlanState *fdw_private,
 146                            Cost *startup_cost, Cost *total_cost);
 147 static int file_acquire_sample_rows(Relation onerel, int elevel,
 148                                                  HeapTuple *rows, int targrows,
 149                                                  double *totalrows, double *totaldeadrows);
 150
 151
 152 /*
 153  * Foreign-data wrapper handler function: return a struct with pointers
 154  * to my callback routines.
 155  */
 156 Datum
 157 file_fdw_handler(PG_FUNCTION_ARGS)
 158 {
 159         FdwRoutine *fdwroutine = makeNode(FdwRoutine);
 160
 161         fdwroutine->GetForeignRelSize = fileGetForeignRelSize;
 162         fdwroutine->GetForeignPaths = fileGetForeignPaths;
 163         fdwroutine->GetForeignPlan = fileGetForeignPlan;
 164         fdwroutine->ExplainForeignScan = fileExplainForeignScan;
 165         fdwroutine->BeginForeignScan = fileBeginForeignScan;
 166         fdwroutine->IterateForeignScan = fileIterateForeignScan;
 167         fdwroutine->ReScanForeignScan = fileReScanForeignScan;
 168         fdwroutine->EndForeignScan = fileEndForeignScan;
 169         fdwroutine->AnalyzeForeignTable = fileAnalyzeForeignTable;
 170
 171         PG_RETURN_POINTER(fdwroutine);
 172 }
 173
 174 /*
 175  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
 176  * USER MAPPING or FOREIGN TABLE that uses file_fdw.
 177  *
 178  * Raise an ERROR if the option or its value is considered invalid.
 179  */
 180 Datum
 181 file_fdw_validator(PG_FUNCTION_ARGS)
 182 {
 183         List       *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
 184         Oid                     catalog = PG_GETARG_OID(1);
 185         char       *filename = NULL;
 186         DefElem    *force_not_null = NULL;
 187         DefElem    *force_null = NULL;
 188         List       *other_options = NIL;
 189         ListCell   *cell;
 190
 191         /*
 192          * Only superusers are allowed to set options of a file_fdw foreign table.
 193          * This is because the filename is one of those options, and we don't want
 194          * non-superusers to be able to determine which file gets read.
 195          *
 196          * Putting this sort of permissions check in a validator is a bit of a
 197          * crock, but there doesn't seem to be any other place that can enforce
 198          * the check more cleanly.
 199          *
 200          * Note that the valid_options[] array disallows setting filename at any
 201          * options level other than foreign table --- otherwise there'd still be a
 202          * security hole.
 203          */
 204         if (catalog == ForeignTableRelationId && !superuser())
 205                 ereport(ERROR,
 206                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 207                                  errmsg("only superuser can change options of a file_fdw foreign table")));
 208
 209         /*
 210          * Check that only options supported by file_fdw, and allowed for the
 211          * current object type, are given.
 212          */
 213         foreach(cell, options_list)
 214         {
 215                 DefElem    *def = (DefElem *) lfirst(cell);
 216
 217                 if (!is_valid_option(def->defname, catalog))
 218                 {
 219                         const struct FileFdwOption *opt;
 220                         StringInfoData buf;
 221
 222                         /*
 223                          * Unknown option specified, complain about it. Provide a hint
 224                          * with list of valid options for the object.
 225                          */
 226                         initStringInfo(&buf);
 227                         for (opt = valid_options; opt->optname; opt++)
 228                         {
 229                                 if (catalog == opt->optcontext)
 230                                         appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
 231                                                                          opt->optname);
 232                         }
 233
 234                         ereport(ERROR,
 235                                         (errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
 236                                          errmsg("invalid option \"%s\"", def->defname),
 237                                          buf.len > 0
 238                                          ? errhint("Valid options in this context are: %s",
 239                                                            buf.data)
 240                                   : errhint("There are no valid options in this context.")));
 241                 }
 242
 243                 /*
 244                  * Separate out filename and column-specific options, since
 245                  * ProcessCopyOptions won't accept them.
 246                  */
 247
 248                 if (strcmp(def->defname, "filename") == 0)
 249                 {
 250                         if (filename)
 251                                 ereport(ERROR,
 252                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 253                                                  errmsg("conflicting or redundant options")));
 254                         filename = defGetString(def);
 255                 }
 256                 /*
 257                  * force_not_null is a boolean option; after validation we can discard
 258                  * it - it will be retrieved later in get_file_fdw_attribute_options()
 259                  */
 260                 else if (strcmp(def->defname, "force_not_null") == 0)
 261                 {
 262                         if (force_not_null)
 263                                 ereport(ERROR,
 264                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 265                                                  errmsg("conflicting or redundant options"),
 266                                                  errhint("option \"force_not_null\" supplied more than once for a column")));
 267                         force_not_null = def;
 268                         /* Don't care what the value is, as long as it's a legal boolean */
 269                         (void) defGetBoolean(def);
 270                 }
 271                 /* See comments for force_not_null above */
 272                 else if (strcmp(def->defname, "force_null") == 0)
 273                 {
 274                         if (force_null)
 275                                 ereport(ERROR,
 276                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 277                                                  errmsg("conflicting or redundant options"),
 278                                                  errhint("option \"force_null\" supplied more than once for a column")));
 279                         force_null = def;
 280                         (void) defGetBoolean(def);
 281                 }
 282                 else
 283                         other_options = lappend(other_options, def);
 284         }
 285
 286         /*
 287          * Now apply the core COPY code's validation logic for more checks.
 288          */
 289         ProcessCopyOptions(NULL, true, other_options);
 290
 291         /*
 292          * Filename option is required for file_fdw foreign tables.
 293          */
 294         if (catalog == ForeignTableRelationId && filename == NULL)
 295                 ereport(ERROR,
 296                                 (errcode(ERRCODE_FDW_DYNAMIC_PARAMETER_VALUE_NEEDED),
 297                                  errmsg("filename is required for file_fdw foreign tables")));
 298
 299         PG_RETURN_VOID();
 300 }
 301
 302 /*
 303  * Check if the provided option is one of the valid options.
 304  * context is the Oid of the catalog holding the object the option is for.
 305  */
 306 static bool
 307 is_valid_option(const char *option, Oid context)
 308 {
 309         const struct FileFdwOption *opt;
 310
 311         for (opt = valid_options; opt->optname; opt++)
 312         {
 313                 if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
 314                         return true;
 315         }
 316         return false;
 317 }
 318
 319 /*
 320  * Fetch the options for a file_fdw foreign table.
 321  *
 322  * We have to separate out "filename" from the other options because
 323  * it must not appear in the options list passed to the core COPY code.
 324  */
 325 static void
 326 fileGetOptions(Oid foreigntableid,
 327                            char **filename, List **other_options)
 328 {
 329         ForeignTable *table;
 330         ForeignServer *server;
 331         ForeignDataWrapper *wrapper;
 332         List       *options;
 333         ListCell   *lc,
 334                            *prev;
 335
 336         /*
 337          * Extract options from FDW objects.  We ignore user mappings because
 338          * file_fdw doesn't have any options that can be specified there.
 339          *
 340          * (XXX Actually, given the current contents of valid_options[], there's
 341          * no point in examining anything except the foreign table's own options.
 342          * Simplify?)
 343          */
 344         table = GetForeignTable(foreigntableid);
 345         server = GetForeignServer(table->serverid);
 346         wrapper = GetForeignDataWrapper(server->fdwid);
 347
 348         options = NIL;
 349         options = list_concat(options, wrapper->options);
 350         options = list_concat(options, server->options);
 351         options = list_concat(options, table->options);
 352         options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
 353
 354         /*
 355          * Separate out the filename.
 356          */
 357         *filename = NULL;
 358         prev = NULL;
 359         foreach(lc, options)
 360         {
 361                 DefElem    *def = (DefElem *) lfirst(lc);
 362
 363                 if (strcmp(def->defname, "filename") == 0)
 364                 {
 365                         *filename = defGetString(def);
 366                         options = list_delete_cell(options, lc, prev);
 367                         break;
 368                 }
 369                 prev = lc;
 370         }
 371
 372         /*
 373          * The validator should have checked that a filename was included in the
 374          * options, but check again, just in case.
 375          */
 376         if (*filename == NULL)
 377                 elog(ERROR, "filename is required for file_fdw foreign tables");
 378
 379         *other_options = options;
 380 }
 381
 382 /*
 383  * Retrieve per-column generic options from pg_attribute and construct a list
 384  * of DefElems representing them.
 385  *
 386  * At the moment we only have "force_not_null", and "force_null",
 387  * which should each be combined into a single DefElem listing all such
 388  * columns, since that's what COPY expects.
 389  */
 390 static List *
 391 get_file_fdw_attribute_options(Oid relid)
 392 {
 393         Relation        rel;
 394         TupleDesc       tupleDesc;
 395         AttrNumber      natts;
 396         AttrNumber      attnum;
 397         List       *fnncolumns = NIL;
 398         List       *fncolumns = NIL;
 399
 400         List *options = NIL;
 401
 402         rel = heap_open(relid, AccessShareLock);
 403         tupleDesc = RelationGetDescr(rel);
 404         natts = tupleDesc->natts;
 405
 406         /* Retrieve FDW options for all user-defined attributes. */
 407         for (attnum = 1; attnum <= natts; attnum++)
 408         {
 409                 Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 410                 List       *options;
 411                 ListCell   *lc;
 412
 413                 /* Skip dropped attributes. */
 414                 if (attr->attisdropped)
 415                         continue;
 416
 417                 options = GetForeignColumnOptions(relid, attnum);
 418                 foreach(lc, options)
 419                 {
 420                         DefElem    *def = (DefElem *) lfirst(lc);
 421
 422                         if (strcmp(def->defname, "force_not_null") == 0)
 423                         {
 424                                 if (defGetBoolean(def))
 425                                 {
 426                                         char       *attname = pstrdup(NameStr(attr->attname));
 427
 428                                         fnncolumns = lappend(fnncolumns, makeString(attname));
 429                                 }
 430                         }
 431                         else if (strcmp(def->defname, "force_null") == 0)
 432                         {
 433                                 if (defGetBoolean(def))
 434                                 {
 435                                         char       *attname = pstrdup(NameStr(attr->attname));
 436
 437                                         fncolumns = lappend(fncolumns, makeString(attname));
 438                                 }
 439                         }
 440                         /* maybe in future handle other options here */
 441                 }
 442         }
 443
 444         heap_close(rel, AccessShareLock);
 445
 446         /* Return DefElem only when some column(s) have force_not_null / force_null options set */
 447         if (fnncolumns != NIL)
 448                 options = lappend(options, makeDefElem("force_not_null", (Node *) fnncolumns));
 449
 450         if (fncolumns != NIL)
 451                 options = lappend(options,makeDefElem("force_null", (Node *) fncolumns));
 452
 453         return options;
 454 }
 455
 456 /*
 457  * fileGetForeignRelSize
 458  *              Obtain relation size estimates for a foreign table
 459  */
 460 static void
 461 fileGetForeignRelSize(PlannerInfo *root,
 462                                           RelOptInfo *baserel,
 463                                           Oid foreigntableid)
 464 {
 465         FileFdwPlanState *fdw_private;
 466
 467         /*
 468          * Fetch options.  We only need filename at this point, but we might as
 469          * well get everything and not need to re-fetch it later in planning.
 470          */
 471         fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
 472         fileGetOptions(foreigntableid,
 473                                    &fdw_private->filename, &fdw_private->options);
 474         baserel->fdw_private = (void *) fdw_private;
 475
 476         /* Estimate relation size */
 477         estimate_size(root, baserel, fdw_private);
 478 }
 479
 480 /*
 481  * fileGetForeignPaths
 482  *              Create possible access paths for a scan on the foreign table
 483  *
 484  *              Currently we don't support any push-down feature, so there is only one
 485  *              possible access path, which simply returns all records in the order in
 486  *              the data file.
 487  */
 488 static void
 489 fileGetForeignPaths(PlannerInfo *root,
 490                                         RelOptInfo *baserel,
 491                                         Oid foreigntableid)
 492 {
 493         FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
 494         Cost            startup_cost;
 495         Cost            total_cost;
 496         List       *columns;
 497         List       *coptions = NIL;
 498
 499         /* Decide whether to selectively perform binary conversion */
 500         if (check_selective_binary_conversion(baserel,
 501                                                                                   foreigntableid,
 502                                                                                   &columns))
 503                 coptions = list_make1(makeDefElem("convert_selectively",
 504                                                                                   (Node *) columns));
 505
 506         /* Estimate costs */
 507         estimate_costs(root, baserel, fdw_private,
 508                                    &startup_cost, &total_cost);
 509
 510         /*
 511          * Create a ForeignPath node and add it as only possible path.  We use the
 512          * fdw_private list of the path to carry the convert_selectively option;
 513          * it will be propagated into the fdw_private list of the Plan node.
 514          */
 515         add_path(baserel, (Path *)
 516                          create_foreignscan_path(root, baserel,
 517                                                                          baserel->rows,
 518                                                                          startup_cost,
 519                                                                          total_cost,
 520                                                                          NIL,           /* no pathkeys */
 521                                                                          NULL,          /* no outer rel either */
 522                                                                          coptions));
 523
 524         /*
 525          * If data file was sorted, and we knew it somehow, we could insert
 526          * appropriate pathkeys into the ForeignPath node to tell the planner
 527          * that.
 528          */
 529 }
 530
 531 /*
 532  * fileGetForeignPlan
 533  *              Create a ForeignScan plan node for scanning the foreign table
 534  */
 535 static ForeignScan *
 536 fileGetForeignPlan(PlannerInfo *root,
 537                                    RelOptInfo *baserel,
 538                                    Oid foreigntableid,
 539                                    ForeignPath *best_path,
 540                                    List *tlist,
 541                                    List *scan_clauses)
 542 {
 543         Index           scan_relid = baserel->relid;
 544
 545         /*
 546          * We have no native ability to evaluate restriction clauses, so we just
 547          * put all the scan_clauses into the plan node's qual list for the
 548          * executor to check.  So all we have to do here is strip RestrictInfo
 549          * nodes from the clauses and ignore pseudoconstants (which will be
 550          * handled elsewhere).
 551          */
 552         scan_clauses = extract_actual_clauses(scan_clauses, false);
 553
 554         /* Create the ForeignScan node */
 555         return make_foreignscan(tlist,
 556                                                         scan_clauses,
 557                                                         scan_relid,
 558                                                         NIL,    /* no expressions to evaluate */
 559                                                         best_path->fdw_private);
 560 }
 561
 562 /*
 563  * fileExplainForeignScan
 564  *              Produce extra output for EXPLAIN
 565  */
 566 static void
 567 fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
 568 {
 569         char       *filename;
 570         List       *options;
 571
 572         /* Fetch options --- we only need filename at this point */
 573         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 574                                    &filename, &options);
 575
 576         ExplainPropertyText("Foreign File", filename, es);
 577
 578         /* Suppress file size if we're not showing cost details */
 579         if (es->costs)
 580         {
 581                 struct stat stat_buf;
 582
 583                 if (stat(filename, &stat_buf) == 0)
 584                         ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
 585                                                                 es);
 586         }
 587 }
 588
 589 /*
 590  * fileBeginForeignScan
 591  *              Initiate access to the file by creating CopyState
 592  */
 593 static void
 594 fileBeginForeignScan(ForeignScanState *node, int eflags)
 595 {
 596         ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
 597         char       *filename;
 598         List       *options;
 599         CopyState       cstate;
 600         FileFdwExecutionState *festate;
 601
 602         /*
 603          * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
 604          */
 605         if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
 606                 return;
 607
 608         /* Fetch options of foreign table */
 609         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 610                                    &filename, &options);
 611
 612         /* Add any options from the plan (currently only convert_selectively) */
 613         options = list_concat(options, plan->fdw_private);
 614
 615         /*
 616          * Create CopyState from FDW options.  We always acquire all columns, so
 617          * as to match the expected ScanTupleSlot signature.
 618          */
 619         cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 620                                                    filename,
 621                                                    false,
 622                                                    NIL,
 623                                                    options);
 624
 625         /*
 626          * Save state in node->fdw_state.  We must save enough information to call
 627          * BeginCopyFrom() again.
 628          */
 629         festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
 630         festate->filename = filename;
 631         festate->options = options;
 632         festate->cstate = cstate;
 633
 634         node->fdw_state = (void *) festate;
 635 }
 636
 637 /*
 638  * fileIterateForeignScan
 639  *              Read next record from the data file and store it into the
 640  *              ScanTupleSlot as a virtual tuple
 641  */
 642 static TupleTableSlot *
 643 fileIterateForeignScan(ForeignScanState *node)
 644 {
 645         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 646         TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
 647         bool            found;
 648         ErrorContextCallback errcallback;
 649
 650         /* Set up callback to identify error line number. */
 651         errcallback.callback = CopyFromErrorCallback;
 652         errcallback.arg = (void *) festate->cstate;
 653         errcallback.previous = error_context_stack;
 654         error_context_stack = &errcallback;
 655
 656         /*
 657          * The protocol for loading a virtual tuple into a slot is first
 658          * ExecClearTuple, then fill the values/isnull arrays, then
 659          * ExecStoreVirtualTuple.  If we don't find another row in the file, we
 660          * just skip the last step, leaving the slot empty as required.
 661          *
 662          * We can pass ExprContext = NULL because we read all columns from the
 663          * file, so no need to evaluate default expressions.
 664          *
 665          * We can also pass tupleOid = NULL because we don't allow oids for
 666          * foreign tables.
 667          */
 668         ExecClearTuple(slot);
 669         found = NextCopyFrom(festate->cstate, NULL,
 670                                                  slot->tts_values, slot->tts_isnull,
 671                                                  NULL);
 672         if (found)
 673                 ExecStoreVirtualTuple(slot);
 674
 675         /* Remove error callback. */
 676         error_context_stack = errcallback.previous;
 677
 678         return slot;
 679 }
 680
 681 /*
 682  * fileReScanForeignScan
 683  *              Rescan table, possibly with new parameters
 684  */
 685 static void
 686 fileReScanForeignScan(ForeignScanState *node)
 687 {
 688         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 689
 690         EndCopyFrom(festate->cstate);
 691
 692         festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 693                                                                         festate->filename,
 694                                                                         false,
 695                                                                         NIL,
 696                                                                         festate->options);
 697 }
 698
 699 /*
 700  * fileEndForeignScan
 701  *              Finish scanning foreign table and dispose objects used for this scan
 702  */
 703 static void
 704 fileEndForeignScan(ForeignScanState *node)
 705 {
 706         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 707
 708         /* if festate is NULL, we are in EXPLAIN; nothing to do */
 709         if (festate)
 710                 EndCopyFrom(festate->cstate);
 711 }
 712
 713 /*
 714  * fileAnalyzeForeignTable
 715  *              Test whether analyzing this foreign table is supported
 716  */
 717 static bool
 718 fileAnalyzeForeignTable(Relation relation,
 719                                                 AcquireSampleRowsFunc *func,
 720                                                 BlockNumber *totalpages)
 721 {
 722         char       *filename;
 723         List       *options;
 724         struct stat stat_buf;
 725
 726         /* Fetch options of foreign table */
 727         fileGetOptions(RelationGetRelid(relation), &filename, &options);
 728
 729         /*
 730          * Get size of the file.  (XXX if we fail here, would it be better to just
 731          * return false to skip analyzing the table?)
 732          */
 733         if (stat(filename, &stat_buf) < 0)
 734                 ereport(ERROR,
 735                                 (errcode_for_file_access(),
 736                                  errmsg("could not stat file \"%s\": %m",
 737                                                 filename)));
 738
 739         /*
 740          * Convert size to pages.  Must return at least 1 so that we can tell
 741          * later on that pg_class.relpages is not default.
 742          */
 743         *totalpages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 744         if (*totalpages < 1)
 745                 *totalpages = 1;
 746
 747         *func = file_acquire_sample_rows;
 748
 749         return true;
 750 }
 751
 752 /*
 753  * check_selective_binary_conversion
 754  *
 755  * Check to see if it's useful to convert only a subset of the file's columns
 756  * to binary.  If so, construct a list of the column names to be converted,
 757  * return that at *columns, and return TRUE.  (Note that it's possible to
 758  * determine that no columns need be converted, for instance with a COUNT(*)
 759  * query.  So we can't use returning a NIL list to indicate failure.)
 760  */
 761 static bool
 762 check_selective_binary_conversion(RelOptInfo *baserel,
 763                                                                   Oid foreigntableid,
 764                                                                   List **columns)
 765 {
 766         ForeignTable *table;
 767         ListCell   *lc;
 768         Relation        rel;
 769         TupleDesc       tupleDesc;
 770         AttrNumber      attnum;
 771         Bitmapset  *attrs_used = NULL;
 772         bool            has_wholerow = false;
 773         int                     numattrs;
 774         int                     i;
 775
 776         *columns = NIL;                         /* default result */
 777
 778         /*
 779          * Check format of the file.  If binary format, this is irrelevant.
 780          */
 781         table = GetForeignTable(foreigntableid);
 782         foreach(lc, table->options)
 783         {
 784                 DefElem    *def = (DefElem *) lfirst(lc);
 785
 786                 if (strcmp(def->defname, "format") == 0)
 787                 {
 788                         char       *format = defGetString(def);
 789
 790                         if (strcmp(format, "binary") == 0)
 791                                 return false;
 792                         break;
 793                 }
 794         }
 795
 796         /* Collect all the attributes needed for joins or final output. */
 797         pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
 798                                    &attrs_used);
 799
 800         /* Add all the attributes used by restriction clauses. */
 801         foreach(lc, baserel->baserestrictinfo)
 802         {
 803                 RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 804
 805                 pull_varattnos((Node *) rinfo->clause, baserel->relid,
 806                                            &attrs_used);
 807         }
 808
 809         /* Convert attribute numbers to column names. */
 810         rel = heap_open(foreigntableid, AccessShareLock);
 811         tupleDesc = RelationGetDescr(rel);
 812
 813         while ((attnum = bms_first_member(attrs_used)) >= 0)
 814         {
 815                 /* Adjust for system attributes. */
 816                 attnum += FirstLowInvalidHeapAttributeNumber;
 817
 818                 if (attnum == 0)
 819                 {
 820                         has_wholerow = true;
 821                         break;
 822                 }
 823
 824                 /* Ignore system attributes. */
 825                 if (attnum < 0)
 826                         continue;
 827
 828                 /* Get user attributes. */
 829                 if (attnum > 0)
 830                 {
 831                         Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 832                         char       *attname = NameStr(attr->attname);
 833
 834                         /* Skip dropped attributes (probably shouldn't see any here). */
 835                         if (attr->attisdropped)
 836                                 continue;
 837                         *columns = lappend(*columns, makeString(pstrdup(attname)));
 838                 }
 839         }
 840
 841         /* Count non-dropped user attributes while we have the tupdesc. */
 842         numattrs = 0;
 843         for (i = 0; i < tupleDesc->natts; i++)
 844         {
 845                 Form_pg_attribute attr = tupleDesc->attrs[i];
 846
 847                 if (attr->attisdropped)
 848                         continue;
 849                 numattrs++;
 850         }
 851
 852         heap_close(rel, AccessShareLock);
 853
 854         /* If there's a whole-row reference, fail: we need all the columns. */
 855         if (has_wholerow)
 856         {
 857                 *columns = NIL;
 858                 return false;
 859         }
 860
 861         /* If all the user attributes are needed, fail. */
 862         if (numattrs == list_length(*columns))
 863         {
 864                 *columns = NIL;
 865                 return false;
 866         }
 867
 868         return true;
 869 }
 870
 871 /*
 872  * Estimate size of a foreign table.
 873  *
 874  * The main result is returned in baserel->rows.  We also set
 875  * fdw_private->pages and fdw_private->ntuples for later use in the cost
 876  * calculation.
 877  */
 878 static void
 879 estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 880                           FileFdwPlanState *fdw_private)
 881 {
 882         struct stat stat_buf;
 883         BlockNumber pages;
 884         double          ntuples;
 885         double          nrows;
 886
 887         /*
 888          * Get size of the file.  It might not be there at plan time, though, in
 889          * which case we have to use a default estimate.
 890          */
 891         if (stat(fdw_private->filename, &stat_buf) < 0)
 892                 stat_buf.st_size = 10 * BLCKSZ;
 893
 894         /*
 895          * Convert size to pages for use in I/O cost estimate later.
 896          */
 897         pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 898         if (pages < 1)
 899                 pages = 1;
 900         fdw_private->pages = pages;
 901
 902         /*
 903          * Estimate the number of tuples in the file.
 904          */
 905         if (baserel->pages > 0)
 906         {
 907                 /*
 908                  * We have # of pages and # of tuples from pg_class (that is, from a
 909                  * previous ANALYZE), so compute a tuples-per-page estimate and scale
 910                  * that by the current file size.
 911                  */
 912                 double          density;
 913
 914                 density = baserel->tuples / (double) baserel->pages;
 915                 ntuples = clamp_row_est(density * (double) pages);
 916         }
 917         else
 918         {
 919                 /*
 920                  * Otherwise we have to fake it.  We back into this estimate using the
 921                  * planner's idea of the relation width; which is bogus if not all
 922                  * columns are being read, not to mention that the text representation
 923                  * of a row probably isn't the same size as its internal
 924                  * representation.      Possibly we could do something better, but the
 925                  * real answer to anyone who complains is "ANALYZE" ...
 926                  */
 927                 int                     tuple_width;
 928
 929                 tuple_width = MAXALIGN(baserel->width) +
 930                         MAXALIGN(sizeof(HeapTupleHeaderData));
 931                 ntuples = clamp_row_est((double) stat_buf.st_size /
 932                                                                 (double) tuple_width);
 933         }
 934         fdw_private->ntuples = ntuples;
 935
 936         /*
 937          * Now estimate the number of rows returned by the scan after applying the
 938          * baserestrictinfo quals.
 939          */
 940         nrows = ntuples *
 941                 clauselist_selectivity(root,
 942                                                            baserel->baserestrictinfo,
 943                                                            0,
 944                                                            JOIN_INNER,
 945                                                            NULL);
 946
 947         nrows = clamp_row_est(nrows);
 948
 949         /* Save the output-rows estimate for the planner */
 950         baserel->rows = nrows;
 951 }
 952
 953 /*
 954  * Estimate costs of scanning a foreign table.
 955  *
 956  * Results are returned in *startup_cost and *total_cost.
 957  */
 958 static void
 959 estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 960                            FileFdwPlanState *fdw_private,
 961                            Cost *startup_cost, Cost *total_cost)
 962 {
 963         BlockNumber pages = fdw_private->pages;
 964         double          ntuples = fdw_private->ntuples;
 965         Cost            run_cost = 0;
 966         Cost            cpu_per_tuple;
 967
 968         /*
 969          * We estimate costs almost the same way as cost_seqscan(), thus assuming
 970          * that I/O costs are equivalent to a regular table file of the same size.
 971          * However, we take per-tuple CPU costs as 10x of a seqscan, to account
 972          * for the cost of parsing records.
 973          */
 974         run_cost += seq_page_cost * pages;
 975
 976         *startup_cost = baserel->baserestrictcost.startup;
 977         cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
 978         run_cost += cpu_per_tuple * ntuples;
 979         *total_cost = *startup_cost + run_cost;
 980 }
 981
 982 /*
 983  * file_acquire_sample_rows -- acquire a random sample of rows from the table
 984  *
 985  * Selected rows are returned in the caller-allocated array rows[],
 986  * which must have at least targrows entries.
 987  * The actual number of rows selected is returned as the function result.
 988  * We also count the total number of rows in the file and return it into
 989  * *totalrows.  Note that *totaldeadrows is always set to 0.
 990  *
 991  * Note that the returned list of rows is not always in order by physical
 992  * position in the file.  Therefore, correlation estimates derived later
 993  * may be meaningless, but it's OK because we don't use the estimates
 994  * currently (the planner only pays attention to correlation for indexscans).
 995  */
 996 static int
 997 file_acquire_sample_rows(Relation onerel, int elevel,
 998                                                  HeapTuple *rows, int targrows,
 999                                                  double *totalrows, double *totaldeadrows)
1000 {
1001         int                     numrows = 0;
1002         double          rowstoskip = -1;        /* -1 means not set yet */
1003         double          rstate;
1004         TupleDesc       tupDesc;
1005         Datum      *values;
1006         bool       *nulls;
1007         bool            found;
1008         char       *filename;
1009         List       *options;
1010         CopyState       cstate;
1011         ErrorContextCallback errcallback;
1012         MemoryContext oldcontext = CurrentMemoryContext;
1013         MemoryContext tupcontext;
1014
1015         Assert(onerel);
1016         Assert(targrows > 0);
1017
1018         tupDesc = RelationGetDescr(onerel);
1019         values = (Datum *) palloc(tupDesc->natts * sizeof(Datum));
1020         nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
1021
1022         /* Fetch options of foreign table */
1023         fileGetOptions(RelationGetRelid(onerel), &filename, &options);
1024
1025         /*
1026          * Create CopyState from FDW options.
1027          */
1028         cstate = BeginCopyFrom(onerel, filename, false, NIL, options);
1029
1030         /*
1031          * Use per-tuple memory context to prevent leak of memory used to read
1032          * rows from the file with Copy routines.
1033          */
1034         tupcontext = AllocSetContextCreate(CurrentMemoryContext,
1035                                                                            "file_fdw temporary context",
1036                                                                            ALLOCSET_DEFAULT_MINSIZE,
1037                                                                            ALLOCSET_DEFAULT_INITSIZE,
1038                                                                            ALLOCSET_DEFAULT_MAXSIZE);
1039
1040         /* Prepare for sampling rows */
1041         rstate = anl_init_selection_state(targrows);
1042
1043         /* Set up callback to identify error line number. */
1044         errcallback.callback = CopyFromErrorCallback;
1045         errcallback.arg = (void *) cstate;
1046         errcallback.previous = error_context_stack;
1047         error_context_stack = &errcallback;
1048
1049         *totalrows = 0;
1050         *totaldeadrows = 0;
1051         for (;;)
1052         {
1053                 /* Check for user-requested abort or sleep */
1054                 vacuum_delay_point();
1055
1056                 /* Fetch next row */
1057                 MemoryContextReset(tupcontext);
1058                 MemoryContextSwitchTo(tupcontext);
1059
1060                 found = NextCopyFrom(cstate, NULL, values, nulls, NULL);
1061
1062                 MemoryContextSwitchTo(oldcontext);
1063
1064                 if (!found)
1065                         break;
1066
1067                 /*
1068                  * The first targrows sample rows are simply copied into the
1069                  * reservoir.  Then we start replacing tuples in the sample until we
1070                  * reach the end of the relation. This algorithm is from Jeff Vitter's
1071                  * paper (see more info in commands/analyze.c).
1072                  */
1073                 if (numrows < targrows)
1074                 {
1075                         rows[numrows++] = heap_form_tuple(tupDesc, values, nulls);
1076                 }
1077                 else
1078                 {
1079                         /*
1080                          * t in Vitter's paper is the number of records already processed.
1081                          * If we need to compute a new S value, we must use the
1082                          * not-yet-incremented value of totalrows as t.
1083                          */
1084                         if (rowstoskip < 0)
1085                                 rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
1086
1087                         if (rowstoskip <= 0)
1088                         {
1089                                 /*
1090                                  * Found a suitable tuple, so save it, replacing one old tuple
1091                                  * at random
1092                                  */
1093                                 int                     k = (int) (targrows * anl_random_fract());
1094
1095                                 Assert(k >= 0 && k < targrows);
1096                                 heap_freetuple(rows[k]);
1097                                 rows[k] = heap_form_tuple(tupDesc, values, nulls);
1098                         }
1099
1100                         rowstoskip -= 1;
1101                 }
1102
1103                 *totalrows += 1;
1104         }
1105
1106         /* Remove error callback. */
1107         error_context_stack = errcallback.previous;
1108
1109         /* Clean up. */
1110         MemoryContextDelete(tupcontext);
1111
1112         EndCopyFrom(cstate);
1113
1114         pfree(values);
1115         pfree(nulls);
1116
1117         /*
1118          * Emit some interesting relation info
1119          */
1120         ereport(elevel,
1121                         (errmsg("\"%s\": file contains %.0f rows; "
1122                                         "%d rows in sample",
1123                                         RelationGetRelationName(onerel),
1124                                         *totalrows, numrows)));
1125
1126         return numrows;
1127 }