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) 2010-2013, PostgreSQL Global Development Group
   7  *
   8  * IDENTIFICATION
   9  *                contrib/file_fdw/file_fdw.c
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #include "postgres.h"
  14
  15 #include <sys/stat.h>
  16 #include <unistd.h>
  17
  18 #include "access/htup_details.h"
  19 #include "access/reloptions.h"
  20 #include "access/sysattr.h"
  21 #include "catalog/pg_foreign_table.h"
  22 #include "commands/copy.h"
  23 #include "commands/defrem.h"
  24 #include "commands/explain.h"
  25 #include "commands/vacuum.h"
  26 #include "foreign/fdwapi.h"
  27 #include "foreign/foreign.h"
  28 #include "miscadmin.h"
  29 #include "nodes/makefuncs.h"
  30 #include "optimizer/cost.h"
  31 #include "optimizer/pathnode.h"
  32 #include "optimizer/planmain.h"
  33 #include "optimizer/restrictinfo.h"
  34 #include "optimizer/var.h"
  35 #include "utils/memutils.h"
  36 #include "utils/rel.h"
  37
  38 PG_MODULE_MAGIC;
  39
  40 /*
  41  * Describes the valid options for objects that use this wrapper.
  42  */
  43 struct FileFdwOption
  44 {
  45         const char *optname;
  46         Oid                     optcontext;             /* Oid of catalog in which option may appear */
  47 };
  48
  49 /*
  50  * Valid options for file_fdw.
  51  * These options are based on the options for COPY FROM command.
  52  * But note that force_not_null is handled as a boolean option attached to
  53  * each column, not as a table option.
  54  *
  55  * Note: If you are adding new option for user mapping, you need to modify
  56  * fileGetOptions(), which currently doesn't bother to look at user mappings.
  57  */
  58 static const struct FileFdwOption valid_options[] = {
  59         /* File options */
  60         {"filename", ForeignTableRelationId},
  61
  62         /* Format options */
  63         /* oids option is not supported */
  64         {"format", ForeignTableRelationId},
  65         {"header", ForeignTableRelationId},
  66         {"delimiter", ForeignTableRelationId},
  67         {"quote", ForeignTableRelationId},
  68         {"escape", ForeignTableRelationId},
  69         {"null", ForeignTableRelationId},
  70         {"encoding", ForeignTableRelationId},
  71         {"force_not_null", AttributeRelationId},
  72
  73         /*
  74          * force_quote is not supported by file_fdw because it's for COPY TO.
  75          */
  76
  77         /* Sentinel */
  78         {NULL, InvalidOid}
  79 };
  80
  81 /*
  82  * FDW-specific information for RelOptInfo.fdw_private.
  83  */
  84 typedef struct FileFdwPlanState
  85 {
  86         char       *filename;           /* file to read */
  87         List       *options;            /* merged COPY options, excluding filename */
  88         BlockNumber pages;                      /* estimate of file's physical size */
  89         double          ntuples;                /* estimate of number of rows in file */
  90 } FileFdwPlanState;
  91
  92 /*
  93  * FDW-specific information for ForeignScanState.fdw_state.
  94  */
  95 typedef struct FileFdwExecutionState
  96 {
  97         char       *filename;           /* file to read */
  98         List       *options;            /* merged COPY options, excluding filename */
  99         CopyState       cstate;                 /* state of reading file */
 100 } FileFdwExecutionState;
 101
 102 /*
 103  * SQL functions
 104  */
 105 extern Datum file_fdw_handler(PG_FUNCTION_ARGS);
 106 extern Datum file_fdw_validator(PG_FUNCTION_ARGS);
 107
 108 PG_FUNCTION_INFO_V1(file_fdw_handler);
 109 PG_FUNCTION_INFO_V1(file_fdw_validator);
 110
 111 /*
 112  * FDW callback routines
 113  */
 114 static void fileGetForeignRelSize(PlannerInfo *root,
 115                                           RelOptInfo *baserel,
 116                                           Oid foreigntableid);
 117 static void fileGetForeignPaths(PlannerInfo *root,
 118                                         RelOptInfo *baserel,
 119                                         Oid foreigntableid);
 120 static ForeignScan *fileGetForeignPlan(PlannerInfo *root,
 121                                    RelOptInfo *baserel,
 122                                    Oid foreigntableid,
 123                                    ForeignPath *best_path,
 124                                    List *tlist,
 125                                    List *scan_clauses);
 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         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 force_not_null, since ProcessCopyOptions
 247                  * won't accept them.  (force_not_null only comes in a boolean
 248                  * per-column flavor here.)
 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                 else if (strcmp(def->defname, "force_not_null") == 0)
 259                 {
 260                         if (force_not_null)
 261                                 ereport(ERROR,
 262                                                 (errcode(ERRCODE_SYNTAX_ERROR),
 263                                                  errmsg("conflicting or redundant options")));
 264                         force_not_null = def;
 265                         /* Don't care what the value is, as long as it's a legal boolean */
 266                         (void) defGetBoolean(def);
 267                 }
 268                 else
 269                         other_options = lappend(other_options, def);
 270         }
 271
 272         /*
 273          * Now apply the core COPY code's validation logic for more checks.
 274          */
 275         ProcessCopyOptions(NULL, true, other_options);
 276
 277         /*
 278          * Filename option is required for file_fdw foreign tables.
 279          */
 280         if (catalog == ForeignTableRelationId && filename == NULL)
 281                 ereport(ERROR,
 282                                 (errcode(ERRCODE_FDW_DYNAMIC_PARAMETER_VALUE_NEEDED),
 283                                  errmsg("filename is required for file_fdw foreign tables")));
 284
 285         PG_RETURN_VOID();
 286 }
 287
 288 /*
 289  * Check if the provided option is one of the valid options.
 290  * context is the Oid of the catalog holding the object the option is for.
 291  */
 292 static bool
 293 is_valid_option(const char *option, Oid context)
 294 {
 295         const struct FileFdwOption *opt;
 296
 297         for (opt = valid_options; opt->optname; opt++)
 298         {
 299                 if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
 300                         return true;
 301         }
 302         return false;
 303 }
 304
 305 /*
 306  * Fetch the options for a file_fdw foreign table.
 307  *
 308  * We have to separate out "filename" from the other options because
 309  * it must not appear in the options list passed to the core COPY code.
 310  */
 311 static void
 312 fileGetOptions(Oid foreigntableid,
 313                            char **filename, List **other_options)
 314 {
 315         ForeignTable *table;
 316         ForeignServer *server;
 317         ForeignDataWrapper *wrapper;
 318         List       *options;
 319         ListCell   *lc,
 320                            *prev;
 321
 322         /*
 323          * Extract options from FDW objects.  We ignore user mappings because
 324          * file_fdw doesn't have any options that can be specified there.
 325          *
 326          * (XXX Actually, given the current contents of valid_options[], there's
 327          * no point in examining anything except the foreign table's own options.
 328          * Simplify?)
 329          */
 330         table = GetForeignTable(foreigntableid);
 331         server = GetForeignServer(table->serverid);
 332         wrapper = GetForeignDataWrapper(server->fdwid);
 333
 334         options = NIL;
 335         options = list_concat(options, wrapper->options);
 336         options = list_concat(options, server->options);
 337         options = list_concat(options, table->options);
 338         options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
 339
 340         /*
 341          * Separate out the filename.
 342          */
 343         *filename = NULL;
 344         prev = NULL;
 345         foreach(lc, options)
 346         {
 347                 DefElem    *def = (DefElem *) lfirst(lc);
 348
 349                 if (strcmp(def->defname, "filename") == 0)
 350                 {
 351                         *filename = defGetString(def);
 352                         options = list_delete_cell(options, lc, prev);
 353                         break;
 354                 }
 355                 prev = lc;
 356         }
 357
 358         /*
 359          * The validator should have checked that a filename was included in the
 360          * options, but check again, just in case.
 361          */
 362         if (*filename == NULL)
 363                 elog(ERROR, "filename is required for file_fdw foreign tables");
 364
 365         *other_options = options;
 366 }
 367
 368 /*
 369  * Retrieve per-column generic options from pg_attribute and construct a list
 370  * of DefElems representing them.
 371  *
 372  * At the moment we only have "force_not_null", which should be combined into
 373  * a single DefElem listing all such columns, since that's what COPY expects.
 374  */
 375 static List *
 376 get_file_fdw_attribute_options(Oid relid)
 377 {
 378         Relation        rel;
 379         TupleDesc       tupleDesc;
 380         AttrNumber      natts;
 381         AttrNumber      attnum;
 382         List       *fnncolumns = NIL;
 383
 384         rel = heap_open(relid, AccessShareLock);
 385         tupleDesc = RelationGetDescr(rel);
 386         natts = tupleDesc->natts;
 387
 388         /* Retrieve FDW options for all user-defined attributes. */
 389         for (attnum = 1; attnum <= natts; attnum++)
 390         {
 391                 Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 392                 List       *options;
 393                 ListCell   *lc;
 394
 395                 /* Skip dropped attributes. */
 396                 if (attr->attisdropped)
 397                         continue;
 398
 399                 options = GetForeignColumnOptions(relid, attnum);
 400                 foreach(lc, options)
 401                 {
 402                         DefElem    *def = (DefElem *) lfirst(lc);
 403
 404                         if (strcmp(def->defname, "force_not_null") == 0)
 405                         {
 406                                 if (defGetBoolean(def))
 407                                 {
 408                                         char       *attname = pstrdup(NameStr(attr->attname));
 409
 410                                         fnncolumns = lappend(fnncolumns, makeString(attname));
 411                                 }
 412                         }
 413                         /* maybe in future handle other options here */
 414                 }
 415         }
 416
 417         heap_close(rel, AccessShareLock);
 418
 419         /* Return DefElem only when some column(s) have force_not_null */
 420         if (fnncolumns != NIL)
 421                 return list_make1(makeDefElem("force_not_null", (Node *) fnncolumns));
 422         else
 423                 return NIL;
 424 }
 425
 426 /*
 427  * fileGetForeignRelSize
 428  *              Obtain relation size estimates for a foreign table
 429  */
 430 static void
 431 fileGetForeignRelSize(PlannerInfo *root,
 432                                           RelOptInfo *baserel,
 433                                           Oid foreigntableid)
 434 {
 435         FileFdwPlanState *fdw_private;
 436
 437         /*
 438          * Fetch options.  We only need filename at this point, but we might as
 439          * well get everything and not need to re-fetch it later in planning.
 440          */
 441         fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
 442         fileGetOptions(foreigntableid,
 443                                    &fdw_private->filename, &fdw_private->options);
 444         baserel->fdw_private = (void *) fdw_private;
 445
 446         /* Estimate relation size */
 447         estimate_size(root, baserel, fdw_private);
 448 }
 449
 450 /*
 451  * fileGetForeignPaths
 452  *              Create possible access paths for a scan on the foreign table
 453  *
 454  *              Currently we don't support any push-down feature, so there is only one
 455  *              possible access path, which simply returns all records in the order in
 456  *              the data file.
 457  */
 458 static void
 459 fileGetForeignPaths(PlannerInfo *root,
 460                                         RelOptInfo *baserel,
 461                                         Oid foreigntableid)
 462 {
 463         FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
 464         Cost            startup_cost;
 465         Cost            total_cost;
 466         List       *columns;
 467         List       *coptions = NIL;
 468
 469         /* Decide whether to selectively perform binary conversion */
 470         if (check_selective_binary_conversion(baserel,
 471                                                                                   foreigntableid,
 472                                                                                   &columns))
 473                 coptions = list_make1(makeDefElem("convert_selectively",
 474                                                                                   (Node *) columns));
 475
 476         /* Estimate costs */
 477         estimate_costs(root, baserel, fdw_private,
 478                                    &startup_cost, &total_cost);
 479
 480         /*
 481          * Create a ForeignPath node and add it as only possible path.  We use the
 482          * fdw_private list of the path to carry the convert_selectively option;
 483          * it will be propagated into the fdw_private list of the Plan node.
 484          */
 485         add_path(baserel, (Path *)
 486                          create_foreignscan_path(root, baserel,
 487                                                                          baserel->rows,
 488                                                                          startup_cost,
 489                                                                          total_cost,
 490                                                                          NIL,           /* no pathkeys */
 491                                                                          NULL,          /* no outer rel either */
 492                                                                          coptions));
 493
 494         /*
 495          * If data file was sorted, and we knew it somehow, we could insert
 496          * appropriate pathkeys into the ForeignPath node to tell the planner
 497          * that.
 498          */
 499 }
 500
 501 /*
 502  * fileGetForeignPlan
 503  *              Create a ForeignScan plan node for scanning the foreign table
 504  */
 505 static ForeignScan *
 506 fileGetForeignPlan(PlannerInfo *root,
 507                                    RelOptInfo *baserel,
 508                                    Oid foreigntableid,
 509                                    ForeignPath *best_path,
 510                                    List *tlist,
 511                                    List *scan_clauses)
 512 {
 513         Index           scan_relid = baserel->relid;
 514
 515         /*
 516          * We have no native ability to evaluate restriction clauses, so we just
 517          * put all the scan_clauses into the plan node's qual list for the
 518          * executor to check.  So all we have to do here is strip RestrictInfo
 519          * nodes from the clauses and ignore pseudoconstants (which will be
 520          * handled elsewhere).
 521          */
 522         scan_clauses = extract_actual_clauses(scan_clauses, false);
 523
 524         /* Create the ForeignScan node */
 525         return make_foreignscan(tlist,
 526                                                         scan_clauses,
 527                                                         scan_relid,
 528                                                         NIL,    /* no expressions to evaluate */
 529                                                         best_path->fdw_private);
 530 }
 531
 532 /*
 533  * fileExplainForeignScan
 534  *              Produce extra output for EXPLAIN
 535  */
 536 static void
 537 fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
 538 {
 539         char       *filename;
 540         List       *options;
 541
 542         /* Fetch options --- we only need filename at this point */
 543         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 544                                    &filename, &options);
 545
 546         ExplainPropertyText("Foreign File", filename, es);
 547
 548         /* Suppress file size if we're not showing cost details */
 549         if (es->costs)
 550         {
 551                 struct stat stat_buf;
 552
 553                 if (stat(filename, &stat_buf) == 0)
 554                         ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
 555                                                                 es);
 556         }
 557 }
 558
 559 /*
 560  * fileBeginForeignScan
 561  *              Initiate access to the file by creating CopyState
 562  */
 563 static void
 564 fileBeginForeignScan(ForeignScanState *node, int eflags)
 565 {
 566         ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
 567         char       *filename;
 568         List       *options;
 569         CopyState       cstate;
 570         FileFdwExecutionState *festate;
 571
 572         /*
 573          * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
 574          */
 575         if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
 576                 return;
 577
 578         /* Fetch options of foreign table */
 579         fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
 580                                    &filename, &options);
 581
 582         /* Add any options from the plan (currently only convert_selectively) */
 583         options = list_concat(options, plan->fdw_private);
 584
 585         /*
 586          * Create CopyState from FDW options.  We always acquire all columns, so
 587          * as to match the expected ScanTupleSlot signature.
 588          */
 589         cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 590                                                    filename,
 591                                                    false,
 592                                                    NIL,
 593                                                    options);
 594
 595         /*
 596          * Save state in node->fdw_state.  We must save enough information to call
 597          * BeginCopyFrom() again.
 598          */
 599         festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
 600         festate->filename = filename;
 601         festate->options = options;
 602         festate->cstate = cstate;
 603
 604         node->fdw_state = (void *) festate;
 605 }
 606
 607 /*
 608  * fileIterateForeignScan
 609  *              Read next record from the data file and store it into the
 610  *              ScanTupleSlot as a virtual tuple
 611  */
 612 static TupleTableSlot *
 613 fileIterateForeignScan(ForeignScanState *node)
 614 {
 615         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 616         TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
 617         bool            found;
 618         ErrorContextCallback errcallback;
 619
 620         /* Set up callback to identify error line number. */
 621         errcallback.callback = CopyFromErrorCallback;
 622         errcallback.arg = (void *) festate->cstate;
 623         errcallback.previous = error_context_stack;
 624         error_context_stack = &errcallback;
 625
 626         /*
 627          * The protocol for loading a virtual tuple into a slot is first
 628          * ExecClearTuple, then fill the values/isnull arrays, then
 629          * ExecStoreVirtualTuple.  If we don't find another row in the file, we
 630          * just skip the last step, leaving the slot empty as required.
 631          *
 632          * We can pass ExprContext = NULL because we read all columns from the
 633          * file, so no need to evaluate default expressions.
 634          *
 635          * We can also pass tupleOid = NULL because we don't allow oids for
 636          * foreign tables.
 637          */
 638         ExecClearTuple(slot);
 639         found = NextCopyFrom(festate->cstate, NULL,
 640                                                  slot->tts_values, slot->tts_isnull,
 641                                                  NULL);
 642         if (found)
 643                 ExecStoreVirtualTuple(slot);
 644
 645         /* Remove error callback. */
 646         error_context_stack = errcallback.previous;
 647
 648         return slot;
 649 }
 650
 651 /*
 652  * fileReScanForeignScan
 653  *              Rescan table, possibly with new parameters
 654  */
 655 static void
 656 fileReScanForeignScan(ForeignScanState *node)
 657 {
 658         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 659
 660         EndCopyFrom(festate->cstate);
 661
 662         festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
 663                                                                         festate->filename,
 664                                                                         false,
 665                                                                         NIL,
 666                                                                         festate->options);
 667 }
 668
 669 /*
 670  * fileEndForeignScan
 671  *              Finish scanning foreign table and dispose objects used for this scan
 672  */
 673 static void
 674 fileEndForeignScan(ForeignScanState *node)
 675 {
 676         FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
 677
 678         /* if festate is NULL, we are in EXPLAIN; nothing to do */
 679         if (festate)
 680                 EndCopyFrom(festate->cstate);
 681 }
 682
 683 /*
 684  * fileAnalyzeForeignTable
 685  *              Test whether analyzing this foreign table is supported
 686  */
 687 static bool
 688 fileAnalyzeForeignTable(Relation relation,
 689                                                 AcquireSampleRowsFunc *func,
 690                                                 BlockNumber *totalpages)
 691 {
 692         char       *filename;
 693         List       *options;
 694         struct stat stat_buf;
 695
 696         /* Fetch options of foreign table */
 697         fileGetOptions(RelationGetRelid(relation), &filename, &options);
 698
 699         /*
 700          * Get size of the file.  (XXX if we fail here, would it be better to just
 701          * return false to skip analyzing the table?)
 702          */
 703         if (stat(filename, &stat_buf) < 0)
 704                 ereport(ERROR,
 705                                 (errcode_for_file_access(),
 706                                  errmsg("could not stat file \"%s\": %m",
 707                                                 filename)));
 708
 709         /*
 710          * Convert size to pages.  Must return at least 1 so that we can tell
 711          * later on that pg_class.relpages is not default.
 712          */
 713         *totalpages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 714         if (*totalpages < 1)
 715                 *totalpages = 1;
 716
 717         *func = file_acquire_sample_rows;
 718
 719         return true;
 720 }
 721
 722 /*
 723  * check_selective_binary_conversion
 724  *
 725  * Check to see if it's useful to convert only a subset of the file's columns
 726  * to binary.  If so, construct a list of the column names to be converted,
 727  * return that at *columns, and return TRUE.  (Note that it's possible to
 728  * determine that no columns need be converted, for instance with a COUNT(*)
 729  * query.  So we can't use returning a NIL list to indicate failure.)
 730  */
 731 static bool
 732 check_selective_binary_conversion(RelOptInfo *baserel,
 733                                                                   Oid foreigntableid,
 734                                                                   List **columns)
 735 {
 736         ForeignTable *table;
 737         ListCell   *lc;
 738         Relation        rel;
 739         TupleDesc       tupleDesc;
 740         AttrNumber      attnum;
 741         Bitmapset  *attrs_used = NULL;
 742         bool            has_wholerow = false;
 743         int                     numattrs;
 744         int                     i;
 745
 746         *columns = NIL;                         /* default result */
 747
 748         /*
 749          * Check format of the file.  If binary format, this is irrelevant.
 750          */
 751         table = GetForeignTable(foreigntableid);
 752         foreach(lc, table->options)
 753         {
 754                 DefElem    *def = (DefElem *) lfirst(lc);
 755
 756                 if (strcmp(def->defname, "format") == 0)
 757                 {
 758                         char       *format = defGetString(def);
 759
 760                         if (strcmp(format, "binary") == 0)
 761                                 return false;
 762                         break;
 763                 }
 764         }
 765
 766         /* Collect all the attributes needed for joins or final output. */
 767         pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
 768                                    &attrs_used);
 769
 770         /* Add all the attributes used by restriction clauses. */
 771         foreach(lc, baserel->baserestrictinfo)
 772         {
 773                 RestrictInfo   *rinfo = (RestrictInfo *) lfirst(lc);
 774
 775                 pull_varattnos((Node *) rinfo->clause, baserel->relid,
 776                                            &attrs_used);
 777         }
 778
 779         /* Convert attribute numbers to column names. */
 780         rel = heap_open(foreigntableid, AccessShareLock);
 781         tupleDesc = RelationGetDescr(rel);
 782
 783         while ((attnum = bms_first_member(attrs_used)) >= 0)
 784         {
 785                 /* Adjust for system attributes. */
 786                 attnum += FirstLowInvalidHeapAttributeNumber;
 787
 788                 if (attnum == 0)
 789                 {
 790                         has_wholerow = true;
 791                         break;
 792                 }
 793
 794                 /* Ignore system attributes. */
 795                 if (attnum < 0)
 796                         continue;
 797
 798                 /* Get user attributes. */
 799                 if (attnum > 0)
 800                 {
 801                         Form_pg_attribute attr = tupleDesc->attrs[attnum - 1];
 802                         char       *attname = NameStr(attr->attname);
 803
 804                         /* Skip dropped attributes (probably shouldn't see any here). */
 805                         if (attr->attisdropped)
 806                                 continue;
 807                         *columns = lappend(*columns, makeString(pstrdup(attname)));
 808                 }
 809         }
 810
 811         /* Count non-dropped user attributes while we have the tupdesc. */
 812         numattrs = 0;
 813         for (i = 0; i < tupleDesc->natts; i++)
 814         {
 815                 Form_pg_attribute attr = tupleDesc->attrs[i];
 816
 817                 if (attr->attisdropped)
 818                         continue;
 819                 numattrs++;
 820         }
 821
 822         heap_close(rel, AccessShareLock);
 823
 824         /* If there's a whole-row reference, fail: we need all the columns. */
 825         if (has_wholerow)
 826         {
 827                 *columns = NIL;
 828                 return false;
 829         }
 830
 831         /* If all the user attributes are needed, fail. */
 832         if (numattrs == list_length(*columns))
 833         {
 834                 *columns = NIL;
 835                 return false;
 836         }
 837
 838         return true;
 839 }
 840
 841 /*
 842  * Estimate size of a foreign table.
 843  *
 844  * The main result is returned in baserel->rows.  We also set
 845  * fdw_private->pages and fdw_private->ntuples for later use in the cost
 846  * calculation.
 847  */
 848 static void
 849 estimate_size(PlannerInfo *root, RelOptInfo *baserel,
 850                           FileFdwPlanState *fdw_private)
 851 {
 852         struct stat stat_buf;
 853         BlockNumber pages;
 854         double          ntuples;
 855         double          nrows;
 856
 857         /*
 858          * Get size of the file.  It might not be there at plan time, though, in
 859          * which case we have to use a default estimate.
 860          */
 861         if (stat(fdw_private->filename, &stat_buf) < 0)
 862                 stat_buf.st_size = 10 * BLCKSZ;
 863
 864         /*
 865          * Convert size to pages for use in I/O cost estimate later.
 866          */
 867         pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
 868         if (pages < 1)
 869                 pages = 1;
 870         fdw_private->pages = pages;
 871
 872         /*
 873          * Estimate the number of tuples in the file.
 874          */
 875         if (baserel->pages > 0)
 876         {
 877                 /*
 878                  * We have # of pages and # of tuples from pg_class (that is, from a
 879                  * previous ANALYZE), so compute a tuples-per-page estimate and scale
 880                  * that by the current file size.
 881                  */
 882                 double          density;
 883
 884                 density = baserel->tuples / (double) baserel->pages;
 885                 ntuples = clamp_row_est(density * (double) pages);
 886         }
 887         else
 888         {
 889                 /*
 890                  * Otherwise we have to fake it.  We back into this estimate using the
 891                  * planner's idea of the relation width; which is bogus if not all
 892                  * columns are being read, not to mention that the text representation
 893                  * of a row probably isn't the same size as its internal
 894                  * representation.      Possibly we could do something better, but the
 895                  * real answer to anyone who complains is "ANALYZE" ...
 896                  */
 897                 int                     tuple_width;
 898
 899                 tuple_width = MAXALIGN(baserel->width) +
 900                         MAXALIGN(sizeof(HeapTupleHeaderData));
 901                 ntuples = clamp_row_est((double) stat_buf.st_size /
 902                                                                 (double) tuple_width);
 903         }
 904         fdw_private->ntuples = ntuples;
 905
 906         /*
 907          * Now estimate the number of rows returned by the scan after applying the
 908          * baserestrictinfo quals.
 909          */
 910         nrows = ntuples *
 911                 clauselist_selectivity(root,
 912                                                            baserel->baserestrictinfo,
 913                                                            0,
 914                                                            JOIN_INNER,
 915                                                            NULL);
 916
 917         nrows = clamp_row_est(nrows);
 918
 919         /* Save the output-rows estimate for the planner */
 920         baserel->rows = nrows;
 921 }
 922
 923 /*
 924  * Estimate costs of scanning a foreign table.
 925  *
 926  * Results are returned in *startup_cost and *total_cost.
 927  */
 928 static void
 929 estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
 930                            FileFdwPlanState *fdw_private,
 931                            Cost *startup_cost, Cost *total_cost)
 932 {
 933         BlockNumber pages = fdw_private->pages;
 934         double          ntuples = fdw_private->ntuples;
 935         Cost            run_cost = 0;
 936         Cost            cpu_per_tuple;
 937
 938         /*
 939          * We estimate costs almost the same way as cost_seqscan(), thus assuming
 940          * that I/O costs are equivalent to a regular table file of the same size.
 941          * However, we take per-tuple CPU costs as 10x of a seqscan, to account
 942          * for the cost of parsing records.
 943          */
 944         run_cost += seq_page_cost * pages;
 945
 946         *startup_cost = baserel->baserestrictcost.startup;
 947         cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
 948         run_cost += cpu_per_tuple * ntuples;
 949         *total_cost = *startup_cost + run_cost;
 950 }
 951
 952 /*
 953  * file_acquire_sample_rows -- acquire a random sample of rows from the table
 954  *
 955  * Selected rows are returned in the caller-allocated array rows[],
 956  * which must have at least targrows entries.
 957  * The actual number of rows selected is returned as the function result.
 958  * We also count the total number of rows in the file and return it into
 959  * *totalrows.  Note that *totaldeadrows is always set to 0.
 960  *
 961  * Note that the returned list of rows is not always in order by physical
 962  * position in the file.  Therefore, correlation estimates derived later
 963  * may be meaningless, but it's OK because we don't use the estimates
 964  * currently (the planner only pays attention to correlation for indexscans).
 965  */
 966 static int
 967 file_acquire_sample_rows(Relation onerel, int elevel,
 968                                                  HeapTuple *rows, int targrows,
 969                                                  double *totalrows, double *totaldeadrows)
 970 {
 971         int                     numrows = 0;
 972         double          rowstoskip = -1;        /* -1 means not set yet */
 973         double          rstate;
 974         TupleDesc       tupDesc;
 975         Datum      *values;
 976         bool       *nulls;
 977         bool            found;
 978         char       *filename;
 979         List       *options;
 980         CopyState       cstate;
 981         ErrorContextCallback errcallback;
 982         MemoryContext oldcontext = CurrentMemoryContext;
 983         MemoryContext tupcontext;
 984
 985         Assert(onerel);
 986         Assert(targrows > 0);
 987
 988         tupDesc = RelationGetDescr(onerel);
 989         values = (Datum *) palloc(tupDesc->natts * sizeof(Datum));
 990         nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
 991
 992         /* Fetch options of foreign table */
 993         fileGetOptions(RelationGetRelid(onerel), &filename, &options);
 994
 995         /*
 996          * Create CopyState from FDW options.
 997          */
 998         cstate = BeginCopyFrom(onerel, filename, false, NIL, options);
 999
1000         /*
1001          * Use per-tuple memory context to prevent leak of memory used to read
1002          * rows from the file with Copy routines.
1003          */
1004         tupcontext = AllocSetContextCreate(CurrentMemoryContext,
1005                                                                            "file_fdw temporary context",
1006                                                                            ALLOCSET_DEFAULT_MINSIZE,
1007                                                                            ALLOCSET_DEFAULT_INITSIZE,
1008                                                                            ALLOCSET_DEFAULT_MAXSIZE);
1009
1010         /* Prepare for sampling rows */
1011         rstate = anl_init_selection_state(targrows);
1012
1013         /* Set up callback to identify error line number. */
1014         errcallback.callback = CopyFromErrorCallback;
1015         errcallback.arg = (void *) cstate;
1016         errcallback.previous = error_context_stack;
1017         error_context_stack = &errcallback;
1018
1019         *totalrows = 0;
1020         *totaldeadrows = 0;
1021         for (;;)
1022         {
1023                 /* Check for user-requested abort or sleep */
1024                 vacuum_delay_point();
1025
1026                 /* Fetch next row */
1027                 MemoryContextReset(tupcontext);
1028                 MemoryContextSwitchTo(tupcontext);
1029
1030                 found = NextCopyFrom(cstate, NULL, values, nulls, NULL);
1031
1032                 MemoryContextSwitchTo(oldcontext);
1033
1034                 if (!found)
1035                         break;
1036
1037                 /*
1038                  * The first targrows sample rows are simply copied into the
1039                  * reservoir.  Then we start replacing tuples in the sample until we
1040                  * reach the end of the relation. This algorithm is from Jeff Vitter's
1041                  * paper (see more info in commands/analyze.c).
1042                  */
1043                 if (numrows < targrows)
1044                 {
1045                         rows[numrows++] = heap_form_tuple(tupDesc, values, nulls);
1046                 }
1047                 else
1048                 {
1049                         /*
1050                          * t in Vitter's paper is the number of records already processed.
1051                          * If we need to compute a new S value, we must use the
1052                          * not-yet-incremented value of totalrows as t.
1053                          */
1054                         if (rowstoskip < 0)
1055                                 rowstoskip = anl_get_next_S(*totalrows, targrows, &rstate);
1056
1057                         if (rowstoskip <= 0)
1058                         {
1059                                 /*
1060                                  * Found a suitable tuple, so save it, replacing one old tuple
1061                                  * at random
1062                                  */
1063                                 int                     k = (int) (targrows * anl_random_fract());
1064
1065                                 Assert(k >= 0 && k < targrows);
1066                                 heap_freetuple(rows[k]);
1067                                 rows[k] = heap_form_tuple(tupDesc, values, nulls);
1068                         }
1069
1070                         rowstoskip -= 1;
1071                 }
1072
1073                 *totalrows += 1;
1074         }
1075
1076         /* Remove error callback. */
1077         error_context_stack = errcallback.previous;
1078
1079         /* Clean up. */
1080         MemoryContextDelete(tupcontext);
1081
1082         EndCopyFrom(cstate);
1083
1084         pfree(values);
1085         pfree(nulls);
1086
1087         /*
1088          * Emit some interesting relation info
1089          */
1090         ereport(elevel,
1091                         (errmsg("\"%s\": file contains %.0f rows; "
1092                                         "%d rows in sample",
1093                                         RelationGetRelationName(onerel),
1094                                         *totalrows, numrows)));
1095
1096         return numrows;
1097 }