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) 2010-2016, 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                                    Plan *outer_plan);
 126 static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
 127 static void fileBeginForeignScan(ForeignScanState *node, int eflags);
 128 static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
 129 static void fileReScanForeignScan(ForeignScanState *node);
 130 static void fileEndForeignScan(ForeignScanState *node);
 131 static bool fileAnalyzeForeignTable(Relation relation,
 132                                                 AcquireSampleRowsFunc *func,
 133                                                 BlockNumber *totalpages);
 134
 135 /*
 136  * Helper functions
 137  */
 138 static bool is_valid_option(const char *option, Oid context);
 139 static void fileGetOptions(Oid foreigntableid,
 140                            char **filename, List **other_options);
 141 static List *get_file_fdw_attribute_options(Oid relid);
 142 static bool check_selective_binary_conversion(RelOptInfo *baserel,
 143                                                                   Oid foreigntableid,
 144                                                                   List **columns);
 145 static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 146                           FileFdwPlanState *fdw_private);
 147 static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 148                            FileFdwPlanState *fdw_private,
 149                            Cost *startup_cost, Cost *total_cost);
 150 static int file_acquire_sample_rows(Relation onerel, int elevel,
 151                                                  HeapTuple *rows, int targrows,
 152                                                  double *totalrows, double *totaldeadrows);
 153
 154
 155 /*
 156  * Foreign-data wrapper handler function: return a struct with pointers
 157  * to my callback routines.
 158  */
 159 Datum
 160 file_fdw_handler(PG_FUNCTION_ARGS)
 161 {
 162         FdwRoutine *fdwroutine = makeNode(FdwRoutine);
 163
 164         fdwroutine->GetForeignRelSize = fileGetForeignRelSize;
 165         fdwroutine->GetForeignPaths = fileGetForeignPaths;
 166         fdwroutine->GetForeignPlan = fileGetForeignPlan;
 167         fdwroutine->ExplainForeignScan = fileExplainForeignScan;
 168         fdwroutine->BeginForeignScan = fileBeginForeignScan;
 169         fdwroutine->IterateForeignScan = fileIterateForeignScan;
 170         fdwroutine->ReScanForeignScan = fileReScanForeignScan;
 171         fdwroutine->EndForeignScan = fileEndForeignScan;
 172         fdwroutine->AnalyzeForeignTable = fileAnalyzeForeignTable;
 173
 174         PG_RETURN_POINTER(fdwroutine);
 175 }
 176
 177 /*
 178  * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
 179  * USER MAPPING or FOREIGN TABLE that uses file_fdw.
 180  *
 181  * Raise an ERROR if the option or its value is considered invalid.
 182  */
 183 Datum
 184 file_fdw_validator(PG_FUNCTION_ARGS)
 185 {
 186         List       *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
 187         Oid                     catalog = PG_GETARG_OID(1);
 188         char       *filename = NULL;
 189         DefElem    *force_not_null = NULL;
 190         DefElem    *force_null = NULL;
 191         List       *other_options = NIL;
 192         ListCell   *cell;
 193
 194         /*
 195          * Only superusers are allowed to set options of a file_fdw foreign table.
 196          * This is because the filename is one of those options, and we don't want
 197          * non-superusers to be able to determine which file gets read.
 198          *
 199          * Putting this sort of permissions check in a validator is a bit of a
 200          * crock, but there doesn't seem to be any other place that can enforce
 201          * the check more cleanly.
 202          *
 203          * Note that the valid_options[] array disallows setting filename at any
 204          * options level other than foreign table --- otherwise there'd still be a
 205          * security hole.
 206          */
 207         if (catalog == ForeignTableRelationId && !superuser())
 208                 ereport(ERROR,
 209                                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 210                                  errmsg("only superuser can change options of a file_fdw foreign table")));
 211
 212         /*
 213          * Check that only options supported by file_fdw, and allowed for the
 214          * current object type, are given.
 215          */
 216         foreach(cell, options_list)
 217         {
 218                 DefElem    *def = (DefElem *) lfirst(cell);
 219
 220                 if (!is_valid_option(def->defname, catalog))
 221                 {
 222                         const struct FileFdwOption *opt;
 223                         StringInfoData buf;
 224
 225                         /*
 226                          * Unknown option specified, complain about it. Provide a hint
 227                          * with list of valid options for the object.
 228                          */
 229                         initStringInfo(&buf);
 230                         for (opt = valid_options; opt->optname; opt++)
 231                         {
 232                                 if (catalog == opt->optcontext)
 233                                         appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
 234                                                                          opt->optname);
 235                         }
 236
 237                         ereport(ERROR,
 238                                         (errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
 239                                          errmsg("invalid option \"%s\"", def->defname),
 240                                          buf.len > 0
 241                                          ? errhint("Valid options in this context are: %s",
 242                                                            buf.data)
 243                                   : errhint("There are no valid options in this context.")));
 244                 }
 245
 246                 /*
 247                  * Separate out filename and column-specific options, since
 248                  * ProcessCopyOptions won't accept them.
 249                  */
 250
 251                 if (strcmp(def->defname, "filename") == 0)
 252                 {
 253                         if (filename)
 254                                 ereport(ERROR,
 255                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 256                                                  errmsg("conflicting or redundant options")));
 257                         filename = defGetString(def);
 258                 }
 259
 260                 /*
 261                  * force_not_null is a boolean option; after validation we can discard
 262                  * it - it will be retrieved later in get_file_fdw_attribute_options()
 263                  */
 264                 else if (strcmp(def->defname, "force_not_null") == 0)
 265                 {
 266                         if (force_not_null)
 267                                 ereport(ERROR,
 268                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 269                                                  errmsg("conflicting or redundant options"),
 270                                                  errhint("option \"force_not_null\" supplied more than once for a column")));
 271                         force_not_null = def;
 272                         /* Don't care what the value is, as long as it's a legal boolean */
 273                         (void) defGetBoolean(def);
 274                 }
 275                 /* See comments for force_not_null above */
 276                 else if (strcmp(def->defname, "force_null") == 0)
 277                 {
 278                         if (force_null)
 279                                 ereport(ERROR,
 280                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 281                                                  errmsg("conflicting or redundant options"),
 282                                                  errhint("option \"force_null\" supplied more than once for a column")));
 283                         force_null = def;
 284                         (void) defGetBoolean(def);
 285                 }
 286                 else
 287                         other_options = lappend(other_options, def);
 288         }
 289
 290         /*
 291          * Now apply the core COPY code's validation logic for more checks.
 292          */
 293         ProcessCopyOptions(NULL, true, other_options);
 294
 295         /*
 296          * Filename option is required for file_fdw foreign tables.
 297          */
 298         if (catalog == ForeignTableRelationId && filename == NULL)
 299                 ereport(ERROR,
 300                                 (errcode(ERRCODE_FDW_DYNAMIC_PARAMETER_VALUE_NEEDED),
 301                                  errmsg("filename is required for file_fdw foreign tables")));
 302
 303         PG_RETURN_VOID();
 304 }
 305
 306 /*
 307  * Check if the provided option is one of the valid options.
 308  * context is the Oid of the catalog holding the object the option is for.
 309  */
 310 static bool
 311 is_valid_option(const char *option, Oid context)
 312 {
 313         const struct FileFdwOption *opt;
 314
 315         for (opt = valid_options; opt->optname; opt++)
 316         {
 317                 if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
 318                         return true;
 319         }
 320         return false;
 321 }
 322
 323 /*
 324  * Fetch the options for a file_fdw foreign table.
 325  *
 326  * We have to separate out "filename" from the other options because
 327  * it must not appear in the options list passed to the core COPY code.
 328  */
 329 static void
 330 fileGetOptions(Oid foreigntableid,
 331                            char **filename, List **other_options)
 332 {
 333         ForeignTable *table;
 334         ForeignServer *server;
 335         ForeignDataWrapper *wrapper;
 336         List       *options;
 337         ListCell   *lc,
 338                            *prev;
 339
 340         /*
 341          * Extract options from FDW objects.  We ignore user mappings because
 342          * file_fdw doesn't have any options that can be specified there.
 343          *
 344          * (XXX Actually, given the current contents of valid_options[], there's
 345          * no point in examining anything except the foreign table's own options.
 346          * Simplify?)
 347          */
 348         table = GetForeignTable(foreigntableid);
 349         server = GetForeignServer(table->serverid);
 350         wrapper = GetForeignDataWrapper(server->fdwid);
 351
 352         options = NIL;
 353         options = list_concat(options, wrapper->options);
 354         options = list_concat(options, server->options);
 355         options = list_concat(options, table->options);
 356         options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
 357
 358         /*
 359          * Separate out the filename.
 360          */
 361         *filename = NULL;
 362         prev = NULL;
 363         foreach(lc, options)
 364         {
 365                 DefElem    *def = (DefElem *) lfirst(lc);
 366
 367                 if (strcmp(def->defname, "filename") == 0)
 368                 {
 369                         *filename = defGetString(def);
 370                         options = list_delete_cell(options, lc, prev);
 371                         break;
 372                 }
 373                 prev = lc;
 374         }
 375
 376         /*
 377          * The validator should have checked that a filename was included in the
 378          * options, but check again, just in case.
 379          */
 380         if (*filename == NULL)
 381                 elog(ERROR, "filename is required for file_fdw foreign tables");
 382
 383         *other_options = options;
 384 }
 385
 386 /*
 387  * Retrieve per-column generic options from pg_attribute and construct a list
 388  * of DefElems representing them.
 389  *
 390  * At the moment we only have "force_not_null", and "force_null",
 391  * which should each be combined into a single DefElem listing all such
 392  * columns, since that's what COPY expects.
 393  */
 394 static List *
 395 get_file_fdw_attribute_options(Oid relid)
 396 {
 397         Relation        rel;
 398         TupleDesc       tupleDesc;
 399         AttrNumber      natts;
 400         AttrNumber      attnum;
 401         List       *fnncolumns = NIL;
 402         List       *fncolumns = NIL;
 403
 404         List       *options = NIL;
 405
 406         rel = heap_open(relid, AccessShareLock);
 407         tupleDesc = RelationGetDescr(rel);
 408         natts = tupleDesc->natts;
 409
 410         /* Retrieve FDW options for all user-defined attributes. */
 411         for (attnum = 1; attnum <= natts; attnum++)
 412         {
 413                 Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 414                 List       *options;
 415                 ListCell   *lc;
 416
 417                 /* Skip dropped attributes. */
 418                 if (attr->attisdropped)
 419                         continue;
 420
 421                 options = GetForeignColumnOptions(relid, attnum);
 422                 foreach(lc, options)
 423                 {
 424                         DefElem    *def = (DefElem *) lfirst(lc);
 425
 426                         if (strcmp(def->defname, "force_not_null") == 0)
 427                         {
 428                                 if (defGetBoolean(def))
 429                                 {
 430                                         char       *attname = pstrdup(NameStr(attr->attname));
 431
 432                                         fnncolumns = lappend(fnncolumns, makeString(attname));
 433                                 }
 434                         }
 435                         else if (strcmp(def->defname, "force_null") == 0)
 436                         {
 437                                 if (defGetBoolean(def))
 438                                 {
 439                                         char       *attname = pstrdup(NameStr(attr->attname));
 440
 441                                         fncolumns = lappend(fncolumns, makeString(attname));
 442                                 }
 443                         }
 444                         /* maybe in future handle other options here */
 445                 }
 446         }
 447
 448         heap_close(rel, AccessShareLock);
 449
 450         /*
 451          * Return DefElem only when some column(s) have force_not_null /
 452          * force_null options set
 453          */
 454         if (fnncolumns != NIL)
 455                 options = lappend(options, makeDefElem("force_not_null", (Node *) fnncolumns));
 456
 457         if (fncolumns != NIL)
 458                 options = lappend(options, makeDefElem("force_null", (Node *) fncolumns));
 459
 460         return options;
 461 }
 462
 463 /*
 464  * fileGetForeignRelSize
 465  *              Obtain relation size estimates for a foreign table
 466  */
 467 static void
 468 fileGetForeignRelSize(PlannerInfo *root,
 469                                           RelOptInfo *baserel,
 470                                           Oid foreigntableid)
 471 {
 472         FileFdwPlanState *fdw_private;
 473
 474         /*
 475          * Fetch options.  We only need filename at this point, but we might as
 476          * well get everything and not need to re-fetch it later in planning.
 477          */
 478         fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
 479         fileGetOptions(foreigntableid,
 480                                    &fdw_private->filename, &fdw_private->options);
 481         baserel->fdw_private = (void *) fdw_private;
 482
 483         /* Estimate relation size */
 484         estimate_size(root, baserel, fdw_private);
 485 }
 486
 487 /*
 488  * fileGetForeignPaths
 489  *              Create possible access paths for a scan on the foreign table
 490  *
 491  *              Currently we don't support any push-down feature, so there is only one
 492  *              possible access path, which simply returns all records in the order in
 493  *              the data file.
 494  */
 495 static void
 496 fileGetForeignPaths(PlannerInfo *root,
 497                                         RelOptInfo *baserel,
 498                                         Oid foreigntableid)
 499 {
 500         FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
 501         Cost            startup_cost;
 502         Cost            total_cost;
 503         List       *columns;
 504         List       *coptions = NIL;
 505
 506         /* Decide whether to selectively perform binary conversion */
 507         if (check_selective_binary_conversion(baserel,
 508                                                                                   foreigntableid,
 509                                                                                   &columns))
 510                 coptions = list_make1(makeDefElem("convert_selectively",
 511                                                                                   (Node *) columns));
 512
 513         /* Estimate costs */
 514         estimate_costs(root, baserel, fdw_private,
 515                                    &startup_cost, &total_cost);
 516
 517         /*
 518          * Create a ForeignPath node and add it as only possible path.  We use the
 519          * fdw_private list of the path to carry the convert_selectively option;
 520          * it will be propagated into the fdw_private list of the Plan node.
 521          */
 522         add_path(baserel, (Path *)
 523                          create_foreignscan_path(root, baserel,
 524                                                                          baserel->rows,
 525                                                                          startup_cost,
 526                                                                          total_cost,
 527                                                                          NIL,           /* no pathkeys */
 528                                                                          NULL,          /* no outer rel either */
 529                                                                          NULL,          /* no extra plan */
 530                                                                          coptions));
 531
 532         /*
 533          * If data file was sorted, and we knew it somehow, we could insert
 534          * appropriate pathkeys into the ForeignPath node to tell the planner
 535          * that.
 536          */
 537 }
 538
 539 /*
 540  * fileGetForeignPlan
 541  *              Create a ForeignScan plan node for scanning the foreign table
 542  */
 543 static ForeignScan *
 544 fileGetForeignPlan(PlannerInfo *root,
 545                                    RelOptInfo *baserel,
 546                                    Oid foreigntableid,
 547                                    ForeignPath *best_path,
 548                                    List *tlist,
 549                                    List *scan_clauses,
 550                                    Plan *outer_plan)
 551 {
 552         Index           scan_relid = baserel->relid;
 553
 554         /*
 555          * We have no native ability to evaluate restriction clauses, so we just
 556          * put all the scan_clauses into the plan node's qual list for the
 557          * executor to check.  So all we have to do here is strip RestrictInfo
 558          * nodes from the clauses and ignore pseudoconstants (which will be
 559          * handled elsewhere).
 560          */
 561         scan_clauses = extract_actual_clauses(scan_clauses, false);
 562
 563         /* Create the ForeignScan node */
 564         return make_foreignscan(tlist,
 565                                                         scan_clauses,
 566                                                         scan_relid,
 567                                                         NIL,    /* no expressions to evaluate */
 568                                                         best_path->fdw_private,
 569                                                         NIL,    /* no custom tlist */
 570                                                         NIL,    /* no remote quals */
 571                                                         outer_plan);
 572 }
 573
 574 /*
 575  * fileExplainForeignScan
 576  *              Produce extra output for EXPLAIN
 577  */
 578 static void
 579 fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
 580 {
 581         char       *filename;
 582         List       *options;
 583
 584         /* Fetch options --- we only need filename at this point */
 585         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 586                                    &filename, &options);
 587
 588         ExplainPropertyText("Foreign File", filename, es);
 589
 590         /* Suppress file size if we're not showing cost details */
 591         if (es->costs)
 592         {
 593                 struct stat stat_buf;
 594
 595                 if (stat(filename, &stat_buf) == 0)
 596                         ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
 597                                                                 es);
 598         }
 599 }
 600
 601 /*
 602  * fileBeginForeignScan
 603  *              Initiate access to the file by creating CopyState
 604  */
 605 static void
 606 fileBeginForeignScan(ForeignScanState *node, int eflags)
 607 {
 608         ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
 609         char       *filename;
 610         List       *options;
 611         CopyState       cstate;
 612         FileFdwExecutionState *festate;
 613
 614         /*
 615          * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
 616          */
 617         if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
 618                 return;
 619
 620         /* Fetch options of foreign table */
 621         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 622                                    &filename, &options);
 623
 624         /* Add any options from the plan (currently only convert_selectively) */
 625         options = list_concat(options, plan->fdw_private);
 626
 627         /*
 628          * Create CopyState from FDW options.  We always acquire all columns, so
 629          * as to match the expected ScanTupleSlot signature.
 630          */
 631         cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 632                                                    filename,
 633                                                    false,
 634                                                    NIL,
 635                                                    options);
 636
 637         /*
 638          * Save state in node->fdw_state.  We must save enough information to call
 639          * BeginCopyFrom() again.
 640          */
 641         festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
 642         festate->filename = filename;
 643         festate->options = options;
 644         festate->cstate = cstate;
 645
 646         node->fdw_state = (void *) festate;
 647 }
 648
 649 /*
 650  * fileIterateForeignScan
 651  *              Read next record from the data file and store it into the
 652  *              ScanTupleSlot as a virtual tuple
 653  */
 654 static TupleTableSlot *
 655 fileIterateForeignScan(ForeignScanState *node)
 656 {
 657         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 658         TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
 659         bool            found;
 660         ErrorContextCallback errcallback;
 661
 662         /* Set up callback to identify error line number. */
 663         errcallback.callback = CopyFromErrorCallback;
 664         errcallback.arg = (void *) festate->cstate;
 665         errcallback.previous = error_context_stack;
 666         error_context_stack = &errcallback;
 667
 668         /*
 669          * The protocol for loading a virtual tuple into a slot is first
 670          * ExecClearTuple, then fill the values/isnull arrays, then
 671          * ExecStoreVirtualTuple.  If we don't find another row in the file, we
 672          * just skip the last step, leaving the slot empty as required.
 673          *
 674          * We can pass ExprContext = NULL because we read all columns from the
 675          * file, so no need to evaluate default expressions.
 676          *
 677          * We can also pass tupleOid = NULL because we don't allow oids for
 678          * foreign tables.
 679          */
 680         ExecClearTuple(slot);
 681         found = NextCopyFrom(festate->cstate, NULL,
 682                                                  slot->tts_values, slot->tts_isnull,
 683                                                  NULL);
 684         if (found)
 685                 ExecStoreVirtualTuple(slot);
 686
 687         /* Remove error callback. */
 688         error_context_stack = errcallback.previous;
 689
 690         return slot;
 691 }
 692
 693 /*
 694  * fileReScanForeignScan
 695  *              Rescan table, possibly with new parameters
 696  */
 697 static void
 698 fileReScanForeignScan(ForeignScanState *node)
 699 {
 700         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 701
 702         EndCopyFrom(festate->cstate);
 703
 704         festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 705                                                                         festate->filename,
 706                                                                         false,
 707                                                                         NIL,
 708                                                                         festate->options);
 709 }
 710
 711 /*
 712  * fileEndForeignScan
 713  *              Finish scanning foreign table and dispose objects used for this scan
 714  */
 715 static void
 716 fileEndForeignScan(ForeignScanState *node)
 717 {
 718         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 719
 720         /* if festate is NULL, we are in EXPLAIN; nothing to do */
 721         if (festate)
 722                 EndCopyFrom(festate->cstate);
 723 }
 724
 725 /*
 726  * fileAnalyzeForeignTable
 727  *              Test whether analyzing this foreign table is supported
 728  */
 729 static bool
 730 fileAnalyzeForeignTable(Relation relation,
 731                                                 AcquireSampleRowsFunc *func,
 732                                                 BlockNumber *totalpages)
 733 {
 734         char       *filename;
 735         List       *options;
 736         struct stat stat_buf;
 737
 738         /* Fetch options of foreign table */
 739         fileGetOptions(RelationGetRelid(relation), &filename, &options);
 740
 741         /*
 742          * Get size of the file.  (XXX if we fail here, would it be better to just
 743          * return false to skip analyzing the table?)
 744          */
 745         if (stat(filename, &stat_buf) < 0)
 746                 ereport(ERROR,
 747                                 (errcode_for_file_access(),
 748                                  errmsg("could not stat file \"%s\": %m",
 749                                                 filename)));
 750
 751         /*
 752          * Convert size to pages.  Must return at least 1 so that we can tell
 753          * later on that pg_class.relpages is not default.
 754          */
 755         *totalpages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 756         if (*totalpages < 1)
 757                 *totalpages = 1;
 758
 759         *func = file_acquire_sample_rows;
 760
 761         return true;
 762 }
 763
 764 /*
 765  * check_selective_binary_conversion
 766  *
 767  * Check to see if it's useful to convert only a subset of the file's columns
 768  * to binary.  If so, construct a list of the column names to be converted,
 769  * return that at *columns, and return TRUE.  (Note that it's possible to
 770  * determine that no columns need be converted, for instance with a COUNT(*)
 771  * query.  So we can't use returning a NIL list to indicate failure.)
 772  */
 773 static bool
 774 check_selective_binary_conversion(RelOptInfo *baserel,
 775                                                                   Oid foreigntableid,
 776                                                                   List **columns)
 777 {
 778         ForeignTable *table;
 779         ListCell   *lc;
 780         Relation        rel;
 781         TupleDesc       tupleDesc;
 782         AttrNumber      attnum;
 783         Bitmapset  *attrs_used = NULL;
 784         bool            has_wholerow = false;
 785         int                     numattrs;
 786         int                     i;
 787
 788         *columns = NIL;                         /* default result */
 789
 790         /*
 791          * Check format of the file.  If binary format, this is irrelevant.
 792          */
 793         table = GetForeignTable(foreigntableid);
 794         foreach(lc, table->options)
 795         {
 796                 DefElem    *def = (DefElem *) lfirst(lc);
 797
 798                 if (strcmp(def->defname, "format") == 0)
 799                 {
 800                         char       *format = defGetString(def);
 801
 802                         if (strcmp(format, "binary") == 0)
 803                                 return false;
 804                         break;
 805                 }
 806         }
 807
 808         /* Collect all the attributes needed for joins or final output. */
 809         pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
 810                                    &attrs_used);
 811
 812         /* Add all the attributes used by restriction clauses. */
 813         foreach(lc, baserel->baserestrictinfo)
 814         {
 815                 RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 816
 817                 pull_varattnos((Node *) rinfo->clause, baserel->relid,
 818                                            &attrs_used);
 819         }
 820
 821         /* Convert attribute numbers to column names. */
 822         rel = heap_open(foreigntableid, AccessShareLock);
 823         tupleDesc = RelationGetDescr(rel);
 824
 825         while ((attnum = bms_first_member(attrs_used)) >= 0)
 826         {
 827                 /* Adjust for system attributes. */
 828                 attnum += FirstLowInvalidHeapAttributeNumber;
 829
 830                 if (attnum == 0)
 831                 {
 832                         has_wholerow = true;
 833                         break;
 834                 }
 835
 836                 /* Ignore system attributes. */
 837                 if (attnum < 0)
 838                         continue;
 839
 840                 /* Get user attributes. */
 841                 if (attnum > 0)
 842                 {
 843                         Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 844                         char       *attname = NameStr(attr->attname);
 845
 846                         /* Skip dropped attributes (probably shouldn't see any here). */
 847                         if (attr->attisdropped)
 848                                 continue;
 849                         *columns = lappend(*columns, makeString(pstrdup(attname)));
 850                 }
 851         }
 852
 853         /* Count non-dropped user attributes while we have the tupdesc. */
 854         numattrs = 0;
 855         for (i = 0; i < tupleDesc->natts; i++)
 856         {
 857                 Form_pg_attribute attr = tupleDesc->attrs[i];
 858
 859                 if (attr->attisdropped)
 860                         continue;
 861                 numattrs++;
 862         }
 863
 864         heap_close(rel, AccessShareLock);
 865
 866         /* If there's a whole-row reference, fail: we need all the columns. */
 867         if (has_wholerow)
 868         {
 869                 *columns = NIL;
 870                 return false;
 871         }
 872
 873         /* If all the user attributes are needed, fail. */
 874         if (numattrs == list_length(*columns))
 875         {
 876                 *columns = NIL;
 877                 return false;
 878         }
 879
 880         return true;
 881 }
 882
 883 /*
 884  * Estimate size of a foreign table.
 885  *
 886  * The main result is returned in baserel->rows.  We also set
 887  * fdw_private->pages and fdw_private->ntuples for later use in the cost
 888  * calculation.
 889  */
 890 static void
 891 estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 892                           FileFdwPlanState *fdw_private)
 893 {
 894         struct stat stat_buf;
 895         BlockNumber pages;
 896         double          ntuples;
 897         double          nrows;
 898
 899         /*
 900          * Get size of the file.  It might not be there at plan time, though, in
 901          * which case we have to use a default estimate.
 902          */
 903         if (stat(fdw_private->filename, &stat_buf) < 0)
 904                 stat_buf.st_size = 10 * BLCKSZ;
 905
 906         /*
 907          * Convert size to pages for use in I/O cost estimate later.
 908          */
 909         pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 910         if (pages < 1)
 911                 pages = 1;
 912         fdw_private->pages = pages;
 913
 914         /*
 915          * Estimate the number of tuples in the file.
 916          */
 917         if (baserel->pages > 0)
 918         {
 919                 /*
 920                  * We have # of pages and # of tuples from pg_class (that is, from a
 921                  * previous ANALYZE), so compute a tuples-per-page estimate and scale
 922                  * that by the current file size.
 923                  */
 924                 double          density;
 925
 926                 density = baserel->tuples / (double) baserel->pages;
 927                 ntuples = clamp_row_est(density * (double) pages);
 928         }
 929         else
 930         {
 931                 /*
 932                  * Otherwise we have to fake it.  We back into this estimate using the
 933                  * planner's idea of the relation width; which is bogus if not all
 934                  * columns are being read, not to mention that the text representation
 935                  * of a row probably isn't the same size as its internal
 936                  * representation.  Possibly we could do something better, but the
 937                  * real answer to anyone who complains is "ANALYZE" ...
 938                  */
 939                 int                     tuple_width;
 940
 941                 tuple_width = MAXALIGN(baserel->width) +
 942                         MAXALIGN(SizeofHeapTupleHeader);
 943                 ntuples = clamp_row_est((double) stat_buf.st_size /
 944                                                                 (double) tuple_width);
 945         }
 946         fdw_private->ntuples = ntuples;
 947
 948         /*
 949          * Now estimate the number of rows returned by the scan after applying the
 950          * baserestrictinfo quals.
 951          */
 952         nrows = ntuples *
 953                 clauselist_selectivity(root,
 954                                                            baserel->baserestrictinfo,
 955                                                            0,
 956                                                            JOIN_INNER,
 957                                                            NULL);
 958
 959         nrows = clamp_row_est(nrows);
 960
 961         /* Save the output-rows estimate for the planner */
 962         baserel->rows = nrows;
 963 }
 964
 965 /*
 966  * Estimate costs of scanning a foreign table.
 967  *
 968  * Results are returned in *startup_cost and *total_cost.
 969  */
 970 static void
 971 estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 972                            FileFdwPlanState *fdw_private,
 973                            Cost *startup_cost, Cost *total_cost)
 974 {
 975         BlockNumber pages = fdw_private->pages;
 976         double          ntuples = fdw_private->ntuples;
 977         Cost            run_cost = 0;
 978         Cost            cpu_per_tuple;
 979
 980         /*
 981          * We estimate costs almost the same way as cost_seqscan(), thus assuming
 982          * that I/O costs are equivalent to a regular table file of the same size.
 983          * However, we take per-tuple CPU costs as 10x of a seqscan, to account
 984          * for the cost of parsing records.
 985          */
 986         run_cost += seq_page_cost * pages;
 987
 988         *startup_cost = baserel->baserestrictcost.startup;
 989         cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
 990         run_cost += cpu_per_tuple * ntuples;
 991         *total_cost = *startup_cost + run_cost;
 992 }
 993
 994 /*
 995  * file_acquire_sample_rows -- acquire a random sample of rows from the table
 996  *
 997  * Selected rows are returned in the caller-allocated array rows[],
 998  * which must have at least targrows entries.
 999  * The actual number of rows selected is returned as the function result.
1000  * We also count the total number of rows in the file and return it into
1001  * *totalrows.  Note that *totaldeadrows is always set to 0.
1002  *
1003  * Note that the returned list of rows is not always in order by physical
1004  * position in the file.  Therefore, correlation estimates derived later
1005  * may be meaningless, but it's OK because we don't use the estimates
1006  * currently (the planner only pays attention to correlation for indexscans).
1007  */
1008 static int
1009 file_acquire_sample_rows(Relation onerel, int elevel,
1010                                                  HeapTuple *rows, int targrows,
1011                                                  double *totalrows, double *totaldeadrows)
1012 {
1013         int                     numrows = 0;
1014         double          rowstoskip = -1;        /* -1 means not set yet */
1015         ReservoirStateData rstate;
1016         TupleDesc       tupDesc;
1017         Datum      *values;
1018         bool       *nulls;
1019         bool            found;
1020         char       *filename;
1021         List       *options;
1022         CopyState       cstate;
1023         ErrorContextCallback errcallback;
1024         MemoryContext oldcontext = CurrentMemoryContext;
1025         MemoryContext tupcontext;
1026
1027         Assert(onerel);
1028         Assert(targrows > 0);
1029
1030         tupDesc = RelationGetDescr(onerel);
1031         values = (Datum *) palloc(tupDesc->natts * sizeof(Datum));
1032         nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
1033
1034         /* Fetch options of foreign table */
1035         fileGetOptions(RelationGetRelid(onerel), &filename, &options);
1036
1037         /*
1038          * Create CopyState from FDW options.
1039          */
1040         cstate = BeginCopyFrom(onerel, filename, false, NIL, options);
1041
1042         /*
1043          * Use per-tuple memory context to prevent leak of memory used to read
1044          * rows from the file with Copy routines.
1045          */
1046         tupcontext = AllocSetContextCreate(CurrentMemoryContext,
1047                                                                            "file_fdw temporary context",
1048                                                                            ALLOCSET_DEFAULT_MINSIZE,
1049                                                                            ALLOCSET_DEFAULT_INITSIZE,
1050                                                                            ALLOCSET_DEFAULT_MAXSIZE);
1051
1052         /* Prepare for sampling rows */
1053         reservoir_init_selection_state(&rstate, targrows);
1054
1055         /* Set up callback to identify error line number. */
1056         errcallback.callback = CopyFromErrorCallback;
1057         errcallback.arg = (void *) cstate;
1058         errcallback.previous = error_context_stack;
1059         error_context_stack = &errcallback;
1060
1061         *totalrows = 0;
1062         *totaldeadrows = 0;
1063         for (;;)
1064         {
1065                 /* Check for user-requested abort or sleep */
1066                 vacuum_delay_point();
1067
1068                 /* Fetch next row */
1069                 MemoryContextReset(tupcontext);
1070                 MemoryContextSwitchTo(tupcontext);
1071
1072                 found = NextCopyFrom(cstate, NULL, values, nulls, NULL);
1073
1074                 MemoryContextSwitchTo(oldcontext);
1075
1076                 if (!found)
1077                         break;
1078
1079                 /*
1080                  * The first targrows sample rows are simply copied into the
1081                  * reservoir.  Then we start replacing tuples in the sample until we
1082                  * reach the end of the relation. This algorithm is from Jeff Vitter's
1083                  * paper (see more info in commands/analyze.c).
1084                  */
1085                 if (numrows < targrows)
1086                 {
1087                         rows[numrows++] = heap_form_tuple(tupDesc, values, nulls);
1088                 }
1089                 else
1090                 {
1091                         /*
1092                          * t in Vitter's paper is the number of records already processed.
1093                          * If we need to compute a new S value, we must use the
1094                          * not-yet-incremented value of totalrows as t.
1095                          */
1096                         if (rowstoskip < 0)
1097                                 rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
1098
1099                         if (rowstoskip <= 0)
1100                         {
1101                                 /*
1102                                  * Found a suitable tuple, so save it, replacing one old tuple
1103                                  * at random
1104                                  */
1105                                 int                     k = (int) (targrows * sampler_random_fract(rstate.randstate));
1106
1107                                 Assert(k >= 0 && k < targrows);
1108                                 heap_freetuple(rows[k]);
1109                                 rows[k] = heap_form_tuple(tupDesc, values, nulls);
1110                         }
1111
1112                         rowstoskip -= 1;
1113                 }
1114
1115                 *totalrows += 1;
1116         }
1117
1118         /* Remove error callback. */
1119         error_context_stack = errcallback.previous;
1120
1121         /* Clean up. */
1122         MemoryContextDelete(tupcontext);
1123
1124         EndCopyFrom(cstate);
1125
1126         pfree(values);
1127         pfree(nulls);
1128
1129         /*
1130          * Emit some interesting relation info
1131          */
1132         ereport(elevel,
1133                         (errmsg("\"%s\": file contains %.0f rows; "
1134                                         "%d rows in sample",
1135                                         RelationGetRelationName(onerel),
1136                                         *totalrows, numrows)));
1137
1138         return numrows;
1139 }