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) 2010-2015, 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 #include "utils/sampling.h"
  38
  39 PG_MODULE_MAGIC;
  40
  41 /*
  42  * Describes the valid options for objects that use this wrapper.
  43  */
  44 struct FileFdwOption
  45 {
  46         const char *optname;
  47         Oid                     optcontext;             /* Oid of catalog in which option may appear */
  48 };
  49
  50 /*
  51  * Valid options for file_fdw.
  52  * These options are based on the options for the COPY FROM command.
  53  * But note that force_not_null and force_null are handled as boolean options
  54  * attached to a column, not as table options.
  55  *
  56  * Note: If you are adding new option for user mapping, you need to modify
  57  * fileGetOptions(), which currently doesn't bother to look at user mappings.
  58  */
  59 static const struct FileFdwOption valid_options[] = {
  60         /* File options */
  61         {"filename", ForeignTableRelationId},
  62
  63         /* Format options */
  64         /* oids option is not supported */
  65         {"format", ForeignTableRelationId},
  66         {"header", ForeignTableRelationId},
  67         {"delimiter", ForeignTableRelationId},
  68         {"quote", ForeignTableRelationId},
  69         {"escape", ForeignTableRelationId},
  70         {"null", ForeignTableRelationId},
  71         {"encoding", ForeignTableRelationId},
  72         {"force_not_null", AttributeRelationId},
  73         {"force_null", AttributeRelationId},
  74
  75         /*
  76          * force_quote is not supported by file_fdw because it's for COPY TO.
  77          */
  78
  79         /* Sentinel */
  80         {NULL, InvalidOid}
  81 };
  82
  83 /*
  84  * FDW-specific information for RelOptInfo.fdw_private.
  85  */
  86 typedef struct FileFdwPlanState
  87 {
  88         char       *filename;           /* file to read */
  89         List       *options;            /* merged COPY options, excluding filename */
  90         BlockNumber pages;                      /* estimate of file's physical size */
  91         double          ntuples;                /* estimate of number of rows in file */
  92 } FileFdwPlanState;
  93
  94 /*
  95  * FDW-specific information for ForeignScanState.fdw_state.
  96  */
  97 typedef struct FileFdwExecutionState
  98 {
  99         char       *filename;           /* file to read */
 100         List       *options;            /* merged COPY options, excluding filename */
 101         CopyState       cstate;                 /* state of reading file */
 102 } FileFdwExecutionState;
 103
 104 /*
 105  * SQL functions
 106  */
 107 PG_FUNCTION_INFO_V1(file_fdw_handler);
 108 PG_FUNCTION_INFO_V1(file_fdw_validator);
 109
 110 /*
 111  * FDW callback routines
 112  */
 113 static void fileGetForeignRelSize(PlannerInfo *root,
 114                                           RelOptInfo *baserel,
 115                                           Oid foreigntableid);
 116 static void fileGetForeignPaths(PlannerInfo *root,
 117                                         RelOptInfo *baserel,
 118                                         Oid foreigntableid);
 119 static ForeignScan *fileGetForeignPlan(PlannerInfo *root,
 120                                    RelOptInfo *baserel,
 121                                    Oid foreigntableid,
 122                                    ForeignPath *best_path,
 123                                    List *tlist,
 124                                    List *scan_clauses);
 125 static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
 126 static void fileBeginForeignScan(ForeignScanState *node, int eflags);
 127 static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
 128 static void fileReScanForeignScan(ForeignScanState *node);
 129 static void fileEndForeignScan(ForeignScanState *node);
 130 static bool fileAnalyzeForeignTable(Relation relation,
 131                                                 AcquireSampleRowsFunc *func,
 132                                                 BlockNumber *totalpages);
 133
 134 /*
 135  * Helper functions
 136  */
 137 static bool is_valid_option(const char *option, Oid context);
 138 static void fileGetOptions(Oid foreigntableid,
 139                            char **filename, List **other_options);
 140 static List *get_file_fdw_attribute_options(Oid relid);
 141 static bool check_selective_binary_conversion(RelOptInfo *baserel,
 142                                                                   Oid foreigntableid,
 143                                                                   List **columns);
 144 static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 145                           FileFdwPlanState *fdw_private);
 146 static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 147                            FileFdwPlanState *fdw_private,
 148                            Cost *startup_cost, Cost *total_cost);
 149 static int file_acquire_sample_rows(Relation onerel, int elevel,
 150                                                  HeapTuple *rows, int targrows,
 151                                                  double *totalrows, double *totaldeadrows);
 152
 153
 154 /*
 155  * Foreign-data wrapper handler function: return a struct with pointers
 156  * to my callback routines.
 157  */
 158 Datum
 159 file_fdw_handler(PG_FUNCTION_ARGS)
 160 {
 161         FdwRoutine *fdwroutine = makeNode(FdwRoutine);
 162
 163         fdwroutine->GetForeignRelSize = fileGetForeignRelSize;
 164         fdwroutine->GetForeignPaths = fileGetForeignPaths;
 165         fdwroutine->GetForeignPlan = fileGetForeignPlan;
 166         fdwroutine->ExplainForeignScan = fileExplainForeignScan;
 167         fdwroutine->BeginForeignScan = fileBeginForeignScan;
 168         fdwroutine->IterateForeignScan = fileIterateForeignScan;
 169         fdwroutine->ReScanForeignScan = fileReScanForeignScan;
 170         fdwroutine->EndForeignScan = fileEndForeignScan;
 171         fdwroutine->AnalyzeForeignTable = fileAnalyzeForeignTable;
 172
 173         PG_RETURN_POINTER(fdwroutine);
 174 }
 175
 176 /*
 177  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
 178  * USER MAPPING or FOREIGN TABLE that uses file_fdw.
 179  *
 180  * Raise an ERROR if the option or its value is considered invalid.
 181  */
 182 Datum
 183 file_fdw_validator(PG_FUNCTION_ARGS)
 184 {
 185         List       *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
 186         Oid                     catalog = PG_GETARG_OID(1);
 187         char       *filename = NULL;
 188         DefElem    *force_not_null = NULL;
 189         DefElem    *force_null = NULL;
 190         List       *other_options = NIL;
 191         ListCell   *cell;
 192
 193         /*
 194          * Only superusers are allowed to set options of a file_fdw foreign table.
 195          * This is because the filename is one of those options, and we don't want
 196          * non-superusers to be able to determine which file gets read.
 197          *
 198          * Putting this sort of permissions check in a validator is a bit of a
 199          * crock, but there doesn't seem to be any other place that can enforce
 200          * the check more cleanly.
 201          *
 202          * Note that the valid_options[] array disallows setting filename at any
 203          * options level other than foreign table --- otherwise there'd still be a
 204          * security hole.
 205          */
 206         if (catalog == ForeignTableRelationId && !superuser())
 207                 ereport(ERROR,
 208                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 209                                  errmsg("only superuser can change options of a file_fdw foreign table")));
 210
 211         /*
 212          * Check that only options supported by file_fdw, and allowed for the
 213          * current object type, are given.
 214          */
 215         foreach(cell, options_list)
 216         {
 217                 DefElem    *def = (DefElem *) lfirst(cell);
 218
 219                 if (!is_valid_option(def->defname, catalog))
 220                 {
 221                         const struct FileFdwOption *opt;
 222                         StringInfoData buf;
 223
 224                         /*
 225                          * Unknown option specified, complain about it. Provide a hint
 226                          * with list of valid options for the object.
 227                          */
 228                         initStringInfo(&buf);
 229                         for (opt = valid_options; opt->optname; opt++)
 230                         {
 231                                 if (catalog == opt->optcontext)
 232                                         appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
 233                                                                          opt->optname);
 234                         }
 235
 236                         ereport(ERROR,
 237                                         (errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
 238                                          errmsg("invalid option \"%s\"", def->defname),
 239                                          buf.len > 0
 240                                          ? errhint("Valid options in this context are: %s",
 241                                                            buf.data)
 242                                   : errhint("There are no valid options in this context.")));
 243                 }
 244
 245                 /*
 246                  * Separate out filename and column-specific options, since
 247                  * ProcessCopyOptions won't accept them.
 248                  */
 249
 250                 if (strcmp(def->defname, "filename") == 0)
 251                 {
 252                         if (filename)
 253                                 ereport(ERROR,
 254                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 255                                                  errmsg("conflicting or redundant options")));
 256                         filename = defGetString(def);
 257                 }
 258
 259                 /*
 260                  * force_not_null is a boolean option; after validation we can discard
 261                  * it - it will be retrieved later in get_file_fdw_attribute_options()
 262                  */
 263                 else if (strcmp(def->defname, "force_not_null") == 0)
 264                 {
 265                         if (force_not_null)
 266                                 ereport(ERROR,
 267                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 268                                                  errmsg("conflicting or redundant options"),
 269                                                  errhint("option \"force_not_null\" supplied more than once for a column")));
 270                         force_not_null = def;
 271                         /* Don't care what the value is, as long as it's a legal boolean */
 272                         (void) defGetBoolean(def);
 273                 }
 274                 /* See comments for force_not_null above */
 275                 else if (strcmp(def->defname, "force_null") == 0)
 276                 {
 277                         if (force_null)
 278                                 ereport(ERROR,
 279                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 280                                                  errmsg("conflicting or redundant options"),
 281                                                  errhint("option \"force_null\" supplied more than once for a column")));
 282                         force_null = def;
 283                         (void) defGetBoolean(def);
 284                 }
 285                 else
 286                         other_options = lappend(other_options, def);
 287         }
 288
 289         /*
 290          * Now apply the core COPY code's validation logic for more checks.
 291          */
 292         ProcessCopyOptions(NULL, true, other_options);
 293
 294         /*
 295          * Filename option is required for file_fdw foreign tables.
 296          */
 297         if (catalog == ForeignTableRelationId && filename == NULL)
 298                 ereport(ERROR,
 299                                 (errcode(ERRCODE_FDW_DYNAMIC_PARAMETER_VALUE_NEEDED),
 300                                  errmsg("filename is required for file_fdw foreign tables")));
 301
 302         PG_RETURN_VOID();
 303 }
 304
 305 /*
 306  * Check if the provided option is one of the valid options.
 307  * context is the Oid of the catalog holding the object the option is for.
 308  */
 309 static bool
 310 is_valid_option(const char *option, Oid context)
 311 {
 312         const struct FileFdwOption *opt;
 313
 314         for (opt = valid_options; opt->optname; opt++)
 315         {
 316                 if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
 317                         return true;
 318         }
 319         return false;
 320 }
 321
 322 /*
 323  * Fetch the options for a file_fdw foreign table.
 324  *
 325  * We have to separate out "filename" from the other options because
 326  * it must not appear in the options list passed to the core COPY code.
 327  */
 328 static void
 329 fileGetOptions(Oid foreigntableid,
 330                            char **filename, List **other_options)
 331 {
 332         ForeignTable *table;
 333         ForeignServer *server;
 334         ForeignDataWrapper *wrapper;
 335         List       *options;
 336         ListCell   *lc,
 337                            *prev;
 338
 339         /*
 340          * Extract options from FDW objects.  We ignore user mappings because
 341          * file_fdw doesn't have any options that can be specified there.
 342          *
 343          * (XXX Actually, given the current contents of valid_options[], there's
 344          * no point in examining anything except the foreign table's own options.
 345          * Simplify?)
 346          */
 347         table = GetForeignTable(foreigntableid);
 348         server = GetForeignServer(table->serverid);
 349         wrapper = GetForeignDataWrapper(server->fdwid);
 350
 351         options = NIL;
 352         options = list_concat(options, wrapper->options);
 353         options = list_concat(options, server->options);
 354         options = list_concat(options, table->options);
 355         options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
 356
 357         /*
 358          * Separate out the filename.
 359          */
 360         *filename = NULL;
 361         prev = NULL;
 362         foreach(lc, options)
 363         {
 364                 DefElem    *def = (DefElem *) lfirst(lc);
 365
 366                 if (strcmp(def->defname, "filename") == 0)
 367                 {
 368                         *filename = defGetString(def);
 369                         options = list_delete_cell(options, lc, prev);
 370                         break;
 371                 }
 372                 prev = lc;
 373         }
 374
 375         /*
 376          * The validator should have checked that a filename was included in the
 377          * options, but check again, just in case.
 378          */
 379         if (*filename == NULL)
 380                 elog(ERROR, "filename is required for file_fdw foreign tables");
 381
 382         *other_options = options;
 383 }
 384
 385 /*
 386  * Retrieve per-column generic options from pg_attribute and construct a list
 387  * of DefElems representing them.
 388  *
 389  * At the moment we only have "force_not_null", and "force_null",
 390  * which should each be combined into a single DefElem listing all such
 391  * columns, since that's what COPY expects.
 392  */
 393 static List *
 394 get_file_fdw_attribute_options(Oid relid)
 395 {
 396         Relation        rel;
 397         TupleDesc       tupleDesc;
 398         AttrNumber      natts;
 399         AttrNumber      attnum;
 400         List       *fnncolumns = NIL;
 401         List       *fncolumns = NIL;
 402
 403         List       *options = NIL;
 404
 405         rel = heap_open(relid, AccessShareLock);
 406         tupleDesc = RelationGetDescr(rel);
 407         natts = tupleDesc->natts;
 408
 409         /* Retrieve FDW options for all user-defined attributes. */
 410         for (attnum = 1; attnum <= natts; attnum++)
 411         {
 412                 Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 413                 List       *options;
 414                 ListCell   *lc;
 415
 416                 /* Skip dropped attributes. */
 417                 if (attr->attisdropped)
 418                         continue;
 419
 420                 options = GetForeignColumnOptions(relid, attnum);
 421                 foreach(lc, options)
 422                 {
 423                         DefElem    *def = (DefElem *) lfirst(lc);
 424
 425                         if (strcmp(def->defname, "force_not_null") == 0)
 426                         {
 427                                 if (defGetBoolean(def))
 428                                 {
 429                                         char       *attname = pstrdup(NameStr(attr->attname));
 430
 431                                         fnncolumns = lappend(fnncolumns, makeString(attname));
 432                                 }
 433                         }
 434                         else if (strcmp(def->defname, "force_null") == 0)
 435                         {
 436                                 if (defGetBoolean(def))
 437                                 {
 438                                         char       *attname = pstrdup(NameStr(attr->attname));
 439
 440                                         fncolumns = lappend(fncolumns, makeString(attname));
 441                                 }
 442                         }
 443                         /* maybe in future handle other options here */
 444                 }
 445         }
 446
 447         heap_close(rel, AccessShareLock);
 448
 449         /*
 450          * Return DefElem only when some column(s) have force_not_null /
 451          * force_null options set
 452          */
 453         if (fnncolumns != NIL)
 454                 options = lappend(options, makeDefElem("force_not_null", (Node *) fnncolumns));
 455
 456         if (fncolumns != NIL)
 457                 options = lappend(options, makeDefElem("force_null", (Node *) fncolumns));
 458
 459         return options;
 460 }
 461
 462 /*
 463  * fileGetForeignRelSize
 464  *              Obtain relation size estimates for a foreign table
 465  */
 466 static void
 467 fileGetForeignRelSize(PlannerInfo *root,
 468                                           RelOptInfo *baserel,
 469                                           Oid foreigntableid)
 470 {
 471         FileFdwPlanState *fdw_private;
 472
 473         /*
 474          * Fetch options.  We only need filename at this point, but we might as
 475          * well get everything and not need to re-fetch it later in planning.
 476          */
 477         fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
 478         fileGetOptions(foreigntableid,
 479                                    &fdw_private->filename, &fdw_private->options);
 480         baserel->fdw_private = (void *) fdw_private;
 481
 482         /* Estimate relation size */
 483         estimate_size(root, baserel, fdw_private);
 484 }
 485
 486 /*
 487  * fileGetForeignPaths
 488  *              Create possible access paths for a scan on the foreign table
 489  *
 490  *              Currently we don't support any push-down feature, so there is only one
 491  *              possible access path, which simply returns all records in the order in
 492  *              the data file.
 493  */
 494 static void
 495 fileGetForeignPaths(PlannerInfo *root,
 496                                         RelOptInfo *baserel,
 497                                         Oid foreigntableid)
 498 {
 499         FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
 500         Cost            startup_cost;
 501         Cost            total_cost;
 502         List       *columns;
 503         List       *coptions = NIL;
 504
 505         /* Decide whether to selectively perform binary conversion */
 506         if (check_selective_binary_conversion(baserel,
 507                                                                                   foreigntableid,
 508                                                                                   &columns))
 509                 coptions = list_make1(makeDefElem("convert_selectively",
 510                                                                                   (Node *) columns));
 511
 512         /* Estimate costs */
 513         estimate_costs(root, baserel, fdw_private,
 514                                    &startup_cost, &total_cost);
 515
 516         /*
 517          * Create a ForeignPath node and add it as only possible path.  We use the
 518          * fdw_private list of the path to carry the convert_selectively option;
 519          * it will be propagated into the fdw_private list of the Plan node.
 520          */
 521         add_path(baserel, (Path *)
 522                          create_foreignscan_path(root, baserel,
 523                                                                          baserel->rows,
 524                                                                          startup_cost,
 525                                                                          total_cost,
 526                                                                          NIL,           /* no pathkeys */
 527                                                                          NULL,          /* no outer rel either */
 528                                                                          coptions));
 529
 530         /*
 531          * If data file was sorted, and we knew it somehow, we could insert
 532          * appropriate pathkeys into the ForeignPath node to tell the planner
 533          * that.
 534          */
 535 }
 536
 537 /*
 538  * fileGetForeignPlan
 539  *              Create a ForeignScan plan node for scanning the foreign table
 540  */
 541 static ForeignScan *
 542 fileGetForeignPlan(PlannerInfo *root,
 543                                    RelOptInfo *baserel,
 544                                    Oid foreigntableid,
 545                                    ForeignPath *best_path,
 546                                    List *tlist,
 547                                    List *scan_clauses)
 548 {
 549         Index           scan_relid = baserel->relid;
 550
 551         /*
 552          * We have no native ability to evaluate restriction clauses, so we just
 553          * put all the scan_clauses into the plan node's qual list for the
 554          * executor to check.  So all we have to do here is strip RestrictInfo
 555          * nodes from the clauses and ignore pseudoconstants (which will be
 556          * handled elsewhere).
 557          */
 558         scan_clauses = extract_actual_clauses(scan_clauses, false);
 559
 560         /* Create the ForeignScan node */
 561         return make_foreignscan(tlist,
 562                                                         scan_clauses,
 563                                                         scan_relid,
 564                                                         NIL,    /* no expressions to evaluate */
 565                                                         best_path->fdw_private,
 566                                                         NIL /* no custom tlist */ );
 567 }
 568
 569 /*
 570  * fileExplainForeignScan
 571  *              Produce extra output for EXPLAIN
 572  */
 573 static void
 574 fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
 575 {
 576         char       *filename;
 577         List       *options;
 578
 579         /* Fetch options --- we only need filename at this point */
 580         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 581                                    &filename, &options);
 582
 583         ExplainPropertyText("Foreign File", filename, es);
 584
 585         /* Suppress file size if we're not showing cost details */
 586         if (es->costs)
 587         {
 588                 struct stat stat_buf;
 589
 590                 if (stat(filename, &stat_buf) == 0)
 591                         ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
 592                                                                 es);
 593         }
 594 }
 595
 596 /*
 597  * fileBeginForeignScan
 598  *              Initiate access to the file by creating CopyState
 599  */
 600 static void
 601 fileBeginForeignScan(ForeignScanState *node, int eflags)
 602 {
 603         ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
 604         char       *filename;
 605         List       *options;
 606         CopyState       cstate;
 607         FileFdwExecutionState *festate;
 608
 609         /*
 610          * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
 611          */
 612         if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
 613                 return;
 614
 615         /* Fetch options of foreign table */
 616         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 617                                    &filename, &options);
 618
 619         /* Add any options from the plan (currently only convert_selectively) */
 620         options = list_concat(options, plan->fdw_private);
 621
 622         /*
 623          * Create CopyState from FDW options.  We always acquire all columns, so
 624          * as to match the expected ScanTupleSlot signature.
 625          */
 626         cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 627                                                    filename,
 628                                                    false,
 629                                                    NIL,
 630                                                    options);
 631
 632         /*
 633          * Save state in node->fdw_state.  We must save enough information to call
 634          * BeginCopyFrom() again.
 635          */
 636         festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
 637         festate->filename = filename;
 638         festate->options = options;
 639         festate->cstate = cstate;
 640
 641         node->fdw_state = (void *) festate;
 642 }
 643
 644 /*
 645  * fileIterateForeignScan
 646  *              Read next record from the data file and store it into the
 647  *              ScanTupleSlot as a virtual tuple
 648  */
 649 static TupleTableSlot *
 650 fileIterateForeignScan(ForeignScanState *node)
 651 {
 652         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 653         TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
 654         bool            found;
 655         ErrorContextCallback errcallback;
 656
 657         /* Set up callback to identify error line number. */
 658         errcallback.callback = CopyFromErrorCallback;
 659         errcallback.arg = (void *) festate->cstate;
 660         errcallback.previous = error_context_stack;
 661         error_context_stack = &errcallback;
 662
 663         /*
 664          * The protocol for loading a virtual tuple into a slot is first
 665          * ExecClearTuple, then fill the values/isnull arrays, then
 666          * ExecStoreVirtualTuple.  If we don't find another row in the file, we
 667          * just skip the last step, leaving the slot empty as required.
 668          *
 669          * We can pass ExprContext = NULL because we read all columns from the
 670          * file, so no need to evaluate default expressions.
 671          *
 672          * We can also pass tupleOid = NULL because we don't allow oids for
 673          * foreign tables.
 674          */
 675         ExecClearTuple(slot);
 676         found = NextCopyFrom(festate->cstate, NULL,
 677                                                  slot->tts_values, slot->tts_isnull,
 678                                                  NULL);
 679         if (found)
 680                 ExecStoreVirtualTuple(slot);
 681
 682         /* Remove error callback. */
 683         error_context_stack = errcallback.previous;
 684
 685         return slot;
 686 }
 687
 688 /*
 689  * fileReScanForeignScan
 690  *              Rescan table, possibly with new parameters
 691  */
 692 static void
 693 fileReScanForeignScan(ForeignScanState *node)
 694 {
 695         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 696
 697         EndCopyFrom(festate->cstate);
 698
 699         festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 700                                                                         festate->filename,
 701                                                                         false,
 702                                                                         NIL,
 703                                                                         festate->options);
 704 }
 705
 706 /*
 707  * fileEndForeignScan
 708  *              Finish scanning foreign table and dispose objects used for this scan
 709  */
 710 static void
 711 fileEndForeignScan(ForeignScanState *node)
 712 {
 713         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 714
 715         /* if festate is NULL, we are in EXPLAIN; nothing to do */
 716         if (festate)
 717                 EndCopyFrom(festate->cstate);
 718 }
 719
 720 /*
 721  * fileAnalyzeForeignTable
 722  *              Test whether analyzing this foreign table is supported
 723  */
 724 static bool
 725 fileAnalyzeForeignTable(Relation relation,
 726                                                 AcquireSampleRowsFunc *func,
 727                                                 BlockNumber *totalpages)
 728 {
 729         char       *filename;
 730         List       *options;
 731         struct stat stat_buf;
 732
 733         /* Fetch options of foreign table */
 734         fileGetOptions(RelationGetRelid(relation), &filename, &options);
 735
 736         /*
 737          * Get size of the file.  (XXX if we fail here, would it be better to just
 738          * return false to skip analyzing the table?)
 739          */
 740         if (stat(filename, &stat_buf) < 0)
 741                 ereport(ERROR,
 742                                 (errcode_for_file_access(),
 743                                  errmsg("could not stat file \"%s\": %m",
 744                                                 filename)));
 745
 746         /*
 747          * Convert size to pages.  Must return at least 1 so that we can tell
 748          * later on that pg_class.relpages is not default.
 749          */
 750         *totalpages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 751         if (*totalpages < 1)
 752                 *totalpages = 1;
 753
 754         *func = file_acquire_sample_rows;
 755
 756         return true;
 757 }
 758
 759 /*
 760  * check_selective_binary_conversion
 761  *
 762  * Check to see if it's useful to convert only a subset of the file's columns
 763  * to binary.  If so, construct a list of the column names to be converted,
 764  * return that at *columns, and return TRUE.  (Note that it's possible to
 765  * determine that no columns need be converted, for instance with a COUNT(*)
 766  * query.  So we can't use returning a NIL list to indicate failure.)
 767  */
 768 static bool
 769 check_selective_binary_conversion(RelOptInfo *baserel,
 770                                                                   Oid foreigntableid,
 771                                                                   List **columns)
 772 {
 773         ForeignTable *table;
 774         ListCell   *lc;
 775         Relation        rel;
 776         TupleDesc       tupleDesc;
 777         AttrNumber      attnum;
 778         Bitmapset  *attrs_used = NULL;
 779         bool            has_wholerow = false;
 780         int                     numattrs;
 781         int                     i;
 782
 783         *columns = NIL;                         /* default result */
 784
 785         /*
 786          * Check format of the file.  If binary format, this is irrelevant.
 787          */
 788         table = GetForeignTable(foreigntableid);
 789         foreach(lc, table->options)
 790         {
 791                 DefElem    *def = (DefElem *) lfirst(lc);
 792
 793                 if (strcmp(def->defname, "format") == 0)
 794                 {
 795                         char       *format = defGetString(def);
 796
 797                         if (strcmp(format, "binary") == 0)
 798                                 return false;
 799                         break;
 800                 }
 801         }
 802
 803         /* Collect all the attributes needed for joins or final output. */
 804         pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
 805                                    &attrs_used);
 806
 807         /* Add all the attributes used by restriction clauses. */
 808         foreach(lc, baserel->baserestrictinfo)
 809         {
 810                 RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 811
 812                 pull_varattnos((Node *) rinfo->clause, baserel->relid,
 813                                            &attrs_used);
 814         }
 815
 816         /* Convert attribute numbers to column names. */
 817         rel = heap_open(foreigntableid, AccessShareLock);
 818         tupleDesc = RelationGetDescr(rel);
 819
 820         while ((attnum = bms_first_member(attrs_used)) >= 0)
 821         {
 822                 /* Adjust for system attributes. */
 823                 attnum += FirstLowInvalidHeapAttributeNumber;
 824
 825                 if (attnum == 0)
 826                 {
 827                         has_wholerow = true;
 828                         break;
 829                 }
 830
 831                 /* Ignore system attributes. */
 832                 if (attnum < 0)
 833                         continue;
 834
 835                 /* Get user attributes. */
 836                 if (attnum > 0)
 837                 {
 838                         Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 839                         char       *attname = NameStr(attr->attname);
 840
 841                         /* Skip dropped attributes (probably shouldn't see any here). */
 842                         if (attr->attisdropped)
 843                                 continue;
 844                         *columns = lappend(*columns, makeString(pstrdup(attname)));
 845                 }
 846         }
 847
 848         /* Count non-dropped user attributes while we have the tupdesc. */
 849         numattrs = 0;
 850         for (i = 0; i < tupleDesc->natts; i++)
 851         {
 852                 Form_pg_attribute attr = tupleDesc->attrs[i];
 853
 854                 if (attr->attisdropped)
 855                         continue;
 856                 numattrs++;
 857         }
 858
 859         heap_close(rel, AccessShareLock);
 860
 861         /* If there's a whole-row reference, fail: we need all the columns. */
 862         if (has_wholerow)
 863         {
 864                 *columns = NIL;
 865                 return false;
 866         }
 867
 868         /* If all the user attributes are needed, fail. */
 869         if (numattrs == list_length(*columns))
 870         {
 871                 *columns = NIL;
 872                 return false;
 873         }
 874
 875         return true;
 876 }
 877
 878 /*
 879  * Estimate size of a foreign table.
 880  *
 881  * The main result is returned in baserel->rows.  We also set
 882  * fdw_private->pages and fdw_private->ntuples for later use in the cost
 883  * calculation.
 884  */
 885 static void
 886 estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 887                           FileFdwPlanState *fdw_private)
 888 {
 889         struct stat stat_buf;
 890         BlockNumber pages;
 891         double          ntuples;
 892         double          nrows;
 893
 894         /*
 895          * Get size of the file.  It might not be there at plan time, though, in
 896          * which case we have to use a default estimate.
 897          */
 898         if (stat(fdw_private->filename, &stat_buf) < 0)
 899                 stat_buf.st_size = 10 * BLCKSZ;
 900
 901         /*
 902          * Convert size to pages for use in I/O cost estimate later.
 903          */
 904         pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 905         if (pages < 1)
 906                 pages = 1;
 907         fdw_private->pages = pages;
 908
 909         /*
 910          * Estimate the number of tuples in the file.
 911          */
 912         if (baserel->pages > 0)
 913         {
 914                 /*
 915                  * We have # of pages and # of tuples from pg_class (that is, from a
 916                  * previous ANALYZE), so compute a tuples-per-page estimate and scale
 917                  * that by the current file size.
 918                  */
 919                 double          density;
 920
 921                 density = baserel->tuples / (double) baserel->pages;
 922                 ntuples = clamp_row_est(density * (double) pages);
 923         }
 924         else
 925         {
 926                 /*
 927                  * Otherwise we have to fake it.  We back into this estimate using the
 928                  * planner's idea of the relation width; which is bogus if not all
 929                  * columns are being read, not to mention that the text representation
 930                  * of a row probably isn't the same size as its internal
 931                  * representation.  Possibly we could do something better, but the
 932                  * real answer to anyone who complains is "ANALYZE" ...
 933                  */
 934                 int                     tuple_width;
 935
 936                 tuple_width = MAXALIGN(baserel->width) +
 937                         MAXALIGN(SizeofHeapTupleHeader);
 938                 ntuples = clamp_row_est((double) stat_buf.st_size /
 939                                                                 (double) tuple_width);
 940         }
 941         fdw_private->ntuples = ntuples;
 942
 943         /*
 944          * Now estimate the number of rows returned by the scan after applying the
 945          * baserestrictinfo quals.
 946          */
 947         nrows = ntuples *
 948                 clauselist_selectivity(root,
 949                                                            baserel->baserestrictinfo,
 950                                                            0,
 951                                                            JOIN_INNER,
 952                                                            NULL);
 953
 954         nrows = clamp_row_est(nrows);
 955
 956         /* Save the output-rows estimate for the planner */
 957         baserel->rows = nrows;
 958 }
 959
 960 /*
 961  * Estimate costs of scanning a foreign table.
 962  *
 963  * Results are returned in *startup_cost and *total_cost.
 964  */
 965 static void
 966 estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 967                            FileFdwPlanState *fdw_private,
 968                            Cost *startup_cost, Cost *total_cost)
 969 {
 970         BlockNumber pages = fdw_private->pages;
 971         double          ntuples = fdw_private->ntuples;
 972         Cost            run_cost = 0;
 973         Cost            cpu_per_tuple;
 974
 975         /*
 976          * We estimate costs almost the same way as cost_seqscan(), thus assuming
 977          * that I/O costs are equivalent to a regular table file of the same size.
 978          * However, we take per-tuple CPU costs as 10x of a seqscan, to account
 979          * for the cost of parsing records.
 980          */
 981         run_cost += seq_page_cost * pages;
 982
 983         *startup_cost = baserel->baserestrictcost.startup;
 984         cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
 985         run_cost += cpu_per_tuple * ntuples;
 986         *total_cost = *startup_cost + run_cost;
 987 }
 988
 989 /*
 990  * file_acquire_sample_rows -- acquire a random sample of rows from the table
 991  *
 992  * Selected rows are returned in the caller-allocated array rows[],
 993  * which must have at least targrows entries.
 994  * The actual number of rows selected is returned as the function result.
 995  * We also count the total number of rows in the file and return it into
 996  * *totalrows.  Note that *totaldeadrows is always set to 0.
 997  *
 998  * Note that the returned list of rows is not always in order by physical
 999  * position in the file.  Therefore, correlation estimates derived later
1000  * may be meaningless, but it's OK because we don't use the estimates
1001  * currently (the planner only pays attention to correlation for indexscans).
1002  */
1003 static int
1004 file_acquire_sample_rows(Relation onerel, int elevel,
1005                                                  HeapTuple *rows, int targrows,
1006                                                  double *totalrows, double *totaldeadrows)
1007 {
1008         int                     numrows = 0;
1009         double          rowstoskip = -1;        /* -1 means not set yet */
1010         ReservoirStateData rstate;
1011         TupleDesc       tupDesc;
1012         Datum      *values;
1013         bool       *nulls;
1014         bool            found;
1015         char       *filename;
1016         List       *options;
1017         CopyState       cstate;
1018         ErrorContextCallback errcallback;
1019         MemoryContext oldcontext = CurrentMemoryContext;
1020         MemoryContext tupcontext;
1021
1022         Assert(onerel);
1023         Assert(targrows > 0);
1024
1025         tupDesc = RelationGetDescr(onerel);
1026         values = (Datum *) palloc(tupDesc->natts * sizeof(Datum));
1027         nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
1028
1029         /* Fetch options of foreign table */
1030         fileGetOptions(RelationGetRelid(onerel), &filename, &options);
1031
1032         /*
1033          * Create CopyState from FDW options.
1034          */
1035         cstate = BeginCopyFrom(onerel, filename, false, NIL, options);
1036
1037         /*
1038          * Use per-tuple memory context to prevent leak of memory used to read
1039          * rows from the file with Copy routines.
1040          */
1041         tupcontext = AllocSetContextCreate(CurrentMemoryContext,
1042                                                                            "file_fdw temporary context",
1043                                                                            ALLOCSET_DEFAULT_MINSIZE,
1044                                                                            ALLOCSET_DEFAULT_INITSIZE,
1045                                                                            ALLOCSET_DEFAULT_MAXSIZE);
1046
1047         /* Prepare for sampling rows */
1048         reservoir_init_selection_state(&rstate, targrows);
1049
1050         /* Set up callback to identify error line number. */
1051         errcallback.callback = CopyFromErrorCallback;
1052         errcallback.arg = (void *) cstate;
1053         errcallback.previous = error_context_stack;
1054         error_context_stack = &errcallback;
1055
1056         *totalrows = 0;
1057         *totaldeadrows = 0;
1058         for (;;)
1059         {
1060                 /* Check for user-requested abort or sleep */
1061                 vacuum_delay_point();
1062
1063                 /* Fetch next row */
1064                 MemoryContextReset(tupcontext);
1065                 MemoryContextSwitchTo(tupcontext);
1066
1067                 found = NextCopyFrom(cstate, NULL, values, nulls, NULL);
1068
1069                 MemoryContextSwitchTo(oldcontext);
1070
1071                 if (!found)
1072                         break;
1073
1074                 /*
1075                  * The first targrows sample rows are simply copied into the
1076                  * reservoir.  Then we start replacing tuples in the sample until we
1077                  * reach the end of the relation. This algorithm is from Jeff Vitter's
1078                  * paper (see more info in commands/analyze.c).
1079                  */
1080                 if (numrows < targrows)
1081                 {
1082                         rows[numrows++] = heap_form_tuple(tupDesc, values, nulls);
1083                 }
1084                 else
1085                 {
1086                         /*
1087                          * t in Vitter's paper is the number of records already processed.
1088                          * If we need to compute a new S value, we must use the
1089                          * not-yet-incremented value of totalrows as t.
1090                          */
1091                         if (rowstoskip < 0)
1092                                 rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
1093
1094                         if (rowstoskip <= 0)
1095                         {
1096                                 /*
1097                                  * Found a suitable tuple, so save it, replacing one old tuple
1098                                  * at random
1099                                  */
1100                                 int                     k = (int) (targrows * sampler_random_fract(rstate.randstate));
1101
1102                                 Assert(k >= 0 && k < targrows);
1103                                 heap_freetuple(rows[k]);
1104                                 rows[k] = heap_form_tuple(tupDesc, values, nulls);
1105                         }
1106
1107                         rowstoskip -= 1;
1108                 }
1109
1110                 *totalrows += 1;
1111         }
1112
1113         /* Remove error callback. */
1114         error_context_stack = errcallback.previous;
1115
1116         /* Clean up. */
1117         MemoryContextDelete(tupcontext);
1118
1119         EndCopyFrom(cstate);
1120
1121         pfree(values);
1122         pfree(nulls);
1123
1124         /*
1125          * Emit some interesting relation info
1126          */
1127         ereport(elevel,
1128                         (errmsg("\"%s\": file contains %.0f rows; "
1129                                         "%d rows in sample",
1130                                         RelationGetRelationName(onerel),
1131                                         *totalrows, numrows)));
1132
1133         return numrows;
1134 }