Adding upstream version 14.5.upstream/14.5upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1225 insertions, 0 deletions

diff --git a/contrib/file_fdw/file_fdw.c b/contrib/file_fdw/file_fdw.c
new file mode 100644
index 0000000..2c2f149
--- /dev/null
+++ b/contrib/file_fdw/file_fdw.c
@@ -0,0 +1,1225 @@
+/*-------------------------------------------------------------------------
+ *
+ * file_fdw.c
+ *		  foreign-data wrapper for server-side flat files (or programs).
+ *
+ * Copyright (c) 2010-2021, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		  contrib/file_fdw/file_fdw.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "access/htup_details.h"
+#include "access/reloptions.h"
+#include "access/sysattr.h"
+#include "access/table.h"
+#include "catalog/pg_authid.h"
+#include "catalog/pg_foreign_table.h"
+#include "commands/copy.h"
+#include "commands/defrem.h"
+#include "commands/explain.h"
+#include "commands/vacuum.h"
+#include "foreign/fdwapi.h"
+#include "foreign/foreign.h"
+#include "miscadmin.h"
+#include "nodes/makefuncs.h"
+#include "optimizer/optimizer.h"
+#include "optimizer/pathnode.h"
+#include "optimizer/planmain.h"
+#include "optimizer/restrictinfo.h"
+#include "utils/acl.h"
+#include "utils/memutils.h"
+#include "utils/rel.h"
+#include "utils/sampling.h"
+
+PG_MODULE_MAGIC;
+
+/*
+ * Describes the valid options for objects that use this wrapper.
+ */
+struct FileFdwOption
+{
+	const char *optname;
+	Oid			optcontext;		/* Oid of catalog in which option may appear */
+};
+
+/*
+ * Valid options for file_fdw.
+ * These options are based on the options for the COPY FROM command.
+ * But note that force_not_null and force_null are handled as boolean options
+ * attached to a column, not as table options.
+ *
+ * Note: If you are adding new option for user mapping, you need to modify
+ * fileGetOptions(), which currently doesn't bother to look at user mappings.
+ */
+static const struct FileFdwOption valid_options[] = {
+	/* Data source options */
+	{"filename", ForeignTableRelationId},
+	{"program", ForeignTableRelationId},
+
+	/* Format options */
+	/* oids option is not supported */
+	{"format", ForeignTableRelationId},
+	{"header", ForeignTableRelationId},
+	{"delimiter", ForeignTableRelationId},
+	{"quote", ForeignTableRelationId},
+	{"escape", ForeignTableRelationId},
+	{"null", ForeignTableRelationId},
+	{"encoding", ForeignTableRelationId},
+	{"force_not_null", AttributeRelationId},
+	{"force_null", AttributeRelationId},
+
+	/*
+	 * force_quote is not supported by file_fdw because it's for COPY TO.
+	 */
+
+	/* Sentinel */
+	{NULL, InvalidOid}
+};
+
+/*
+ * FDW-specific information for RelOptInfo.fdw_private.
+ */
+typedef struct FileFdwPlanState
+{
+	char	   *filename;		/* file or program to read from */
+	bool		is_program;		/* true if filename represents an OS command */
+	List	   *options;		/* merged COPY options, excluding filename and
+								 * is_program */
+	BlockNumber pages;			/* estimate of file's physical size */
+	double		ntuples;		/* estimate of number of data rows */
+} FileFdwPlanState;
+
+/*
+ * FDW-specific information for ForeignScanState.fdw_state.
+ */
+typedef struct FileFdwExecutionState
+{
+	char	   *filename;		/* file or program to read from */
+	bool		is_program;		/* true if filename represents an OS command */
+	List	   *options;		/* merged COPY options, excluding filename and
+								 * is_program */
+	CopyFromState cstate;		/* COPY execution state */
+} FileFdwExecutionState;
+
+/*
+ * SQL functions
+ */
+PG_FUNCTION_INFO_V1(file_fdw_handler);
+PG_FUNCTION_INFO_V1(file_fdw_validator);
+
+/*
+ * FDW callback routines
+ */
+static void fileGetForeignRelSize(PlannerInfo *root,
+								  RelOptInfo *baserel,
+								  Oid foreigntableid);
+static void fileGetForeignPaths(PlannerInfo *root,
+								RelOptInfo *baserel,
+								Oid foreigntableid);
+static ForeignScan *fileGetForeignPlan(PlannerInfo *root,
+									   RelOptInfo *baserel,
+									   Oid foreigntableid,
+									   ForeignPath *best_path,
+									   List *tlist,
+									   List *scan_clauses,
+									   Plan *outer_plan);
+static void fileExplainForeignScan(ForeignScanState *node, ExplainState *es);
+static void fileBeginForeignScan(ForeignScanState *node, int eflags);
+static TupleTableSlot *fileIterateForeignScan(ForeignScanState *node);
+static void fileReScanForeignScan(ForeignScanState *node);
+static void fileEndForeignScan(ForeignScanState *node);
+static bool fileAnalyzeForeignTable(Relation relation,
+									AcquireSampleRowsFunc *func,
+									BlockNumber *totalpages);
+static bool fileIsForeignScanParallelSafe(PlannerInfo *root, RelOptInfo *rel,
+										  RangeTblEntry *rte);
+
+/*
+ * Helper functions
+ */
+static bool is_valid_option(const char *option, Oid context);
+static void fileGetOptions(Oid foreigntableid,
+						   char **filename,
+						   bool *is_program,
+						   List **other_options);
+static List *get_file_fdw_attribute_options(Oid relid);
+static bool check_selective_binary_conversion(RelOptInfo *baserel,
+											  Oid foreigntableid,
+											  List **columns);
+static void estimate_size(PlannerInfo *root, RelOptInfo *baserel,
+						  FileFdwPlanState *fdw_private);
+static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+						   FileFdwPlanState *fdw_private,
+						   Cost *startup_cost, Cost *total_cost);
+static int	file_acquire_sample_rows(Relation onerel, int elevel,
+									 HeapTuple *rows, int targrows,
+									 double *totalrows, double *totaldeadrows);
+
+
+/*
+ * Foreign-data wrapper handler function: return a struct with pointers
+ * to my callback routines.
+ */
+Datum
+file_fdw_handler(PG_FUNCTION_ARGS)
+{
+	FdwRoutine *fdwroutine = makeNode(FdwRoutine);
+
+	fdwroutine->GetForeignRelSize = fileGetForeignRelSize;
+	fdwroutine->GetForeignPaths = fileGetForeignPaths;
+	fdwroutine->GetForeignPlan = fileGetForeignPlan;
+	fdwroutine->ExplainForeignScan = fileExplainForeignScan;
+	fdwroutine->BeginForeignScan = fileBeginForeignScan;
+	fdwroutine->IterateForeignScan = fileIterateForeignScan;
+	fdwroutine->ReScanForeignScan = fileReScanForeignScan;
+	fdwroutine->EndForeignScan = fileEndForeignScan;
+	fdwroutine->AnalyzeForeignTable = fileAnalyzeForeignTable;
+	fdwroutine->IsForeignScanParallelSafe = fileIsForeignScanParallelSafe;
+
+	PG_RETURN_POINTER(fdwroutine);
+}
+
+/*
+ * Validate the generic options given to a FOREIGN DATA WRAPPER, SERVER,
+ * USER MAPPING or FOREIGN TABLE that uses file_fdw.
+ *
+ * Raise an ERROR if the option or its value is considered invalid.
+ */
+Datum
+file_fdw_validator(PG_FUNCTION_ARGS)
+{
+	List	   *options_list = untransformRelOptions(PG_GETARG_DATUM(0));
+	Oid			catalog = PG_GETARG_OID(1);
+	char	   *filename = NULL;
+	DefElem    *force_not_null = NULL;
+	DefElem    *force_null = NULL;
+	List	   *other_options = NIL;
+	ListCell   *cell;
+
+	/*
+	 * Check that only options supported by file_fdw, and allowed for the
+	 * current object type, are given.
+	 */
+	foreach(cell, options_list)
+	{
+		DefElem    *def = (DefElem *) lfirst(cell);
+
+		if (!is_valid_option(def->defname, catalog))
+		{
+			const struct FileFdwOption *opt;
+			StringInfoData buf;
+
+			/*
+			 * Unknown option specified, complain about it. Provide a hint
+			 * with list of valid options for the object.
+			 */
+			initStringInfo(&buf);
+			for (opt = valid_options; opt->optname; opt++)
+			{
+				if (catalog == opt->optcontext)
+					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
+									 opt->optname);
+			}
+
+			ereport(ERROR,
+					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
+					 errmsg("invalid option \"%s\"", def->defname),
+					 buf.len > 0
+					 ? errhint("Valid options in this context are: %s",
+							   buf.data)
+					 : errhint("There are no valid options in this context.")));
+		}
+
+		/*
+		 * Separate out filename, program, and column-specific options, since
+		 * ProcessCopyOptions won't accept them.
+		 */
+		if (strcmp(def->defname, "filename") == 0 ||
+			strcmp(def->defname, "program") == 0)
+		{
+			if (filename)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+
+			/*
+			 * Check permissions for changing which file or program is used by
+			 * the file_fdw.
+			 *
+			 * Only members of the role 'pg_read_server_files' are allowed to
+			 * set the 'filename' option of a file_fdw foreign table, while
+			 * only members of the role 'pg_execute_server_program' are
+			 * allowed to set the 'program' option.  This is because we don't
+			 * want regular users to be able to control which file gets read
+			 * or which program gets executed.
+			 *
+			 * Putting this sort of permissions check in a validator is a bit
+			 * of a crock, but there doesn't seem to be any other place that
+			 * can enforce the check more cleanly.
+			 *
+			 * Note that the valid_options[] array disallows setting filename
+			 * and program at any options level other than foreign table ---
+			 * otherwise there'd still be a security hole.
+			 */
+			if (strcmp(def->defname, "filename") == 0 &&
+				!is_member_of_role(GetUserId(), ROLE_PG_READ_SERVER_FILES))
+				ereport(ERROR,
+						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+						 errmsg("only superuser or a member of the pg_read_server_files role may specify the filename option of a file_fdw foreign table")));
+
+			if (strcmp(def->defname, "program") == 0 &&
+				!is_member_of_role(GetUserId(), ROLE_PG_EXECUTE_SERVER_PROGRAM))
+				ereport(ERROR,
+						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+						 errmsg("only superuser or a member of the pg_execute_server_program role may specify the program option of a file_fdw foreign table")));
+
+			filename = defGetString(def);
+		}
+
+		/*
+		 * force_not_null is a boolean option; after validation we can discard
+		 * it - it will be retrieved later in get_file_fdw_attribute_options()
+		 */
+		else if (strcmp(def->defname, "force_not_null") == 0)
+		{
+			if (force_not_null)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options"),
+						 errhint("Option \"force_not_null\" supplied more than once for a column.")));
+			force_not_null = def;
+			/* Don't care what the value is, as long as it's a legal boolean */
+			(void) defGetBoolean(def);
+		}
+		/* See comments for force_not_null above */
+		else if (strcmp(def->defname, "force_null") == 0)
+		{
+			if (force_null)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options"),
+						 errhint("Option \"force_null\" supplied more than once for a column.")));
+			force_null = def;
+			(void) defGetBoolean(def);
+		}
+		else
+			other_options = lappend(other_options, def);
+	}
+
+	/*
+	 * Now apply the core COPY code's validation logic for more checks.
+	 */
+	ProcessCopyOptions(NULL, NULL, true, other_options);
+
+	/*
+	 * Either filename or program option is required for file_fdw foreign
+	 * tables.
+	 */
+	if (catalog == ForeignTableRelationId && filename == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FDW_DYNAMIC_PARAMETER_VALUE_NEEDED),
+				 errmsg("either filename or program is required for file_fdw foreign tables")));
+
+	PG_RETURN_VOID();
+}
+
+/*
+ * Check if the provided option is one of the valid options.
+ * context is the Oid of the catalog holding the object the option is for.
+ */
+static bool
+is_valid_option(const char *option, Oid context)
+{
+	const struct FileFdwOption *opt;
+
+	for (opt = valid_options; opt->optname; opt++)
+	{
+		if (context == opt->optcontext && strcmp(opt->optname, option) == 0)
+			return true;
+	}
+	return false;
+}
+
+/*
+ * Fetch the options for a file_fdw foreign table.
+ *
+ * We have to separate out filename/program from the other options because
+ * those must not appear in the options list passed to the core COPY code.
+ */
+static void
+fileGetOptions(Oid foreigntableid,
+			   char **filename, bool *is_program, List **other_options)
+{
+	ForeignTable *table;
+	ForeignServer *server;
+	ForeignDataWrapper *wrapper;
+	List	   *options;
+	ListCell   *lc;
+
+	/*
+	 * Extract options from FDW objects.  We ignore user mappings because
+	 * file_fdw doesn't have any options that can be specified there.
+	 *
+	 * (XXX Actually, given the current contents of valid_options[], there's
+	 * no point in examining anything except the foreign table's own options.
+	 * Simplify?)
+	 */
+	table = GetForeignTable(foreigntableid);
+	server = GetForeignServer(table->serverid);
+	wrapper = GetForeignDataWrapper(server->fdwid);
+
+	options = NIL;
+	options = list_concat(options, wrapper->options);
+	options = list_concat(options, server->options);
+	options = list_concat(options, table->options);
+	options = list_concat(options, get_file_fdw_attribute_options(foreigntableid));
+
+	/*
+	 * Separate out the filename or program option (we assume there is only
+	 * one).
+	 */
+	*filename = NULL;
+	*is_program = false;
+	foreach(lc, options)
+	{
+		DefElem    *def = (DefElem *) lfirst(lc);
+
+		if (strcmp(def->defname, "filename") == 0)
+		{
+			*filename = defGetString(def);
+			options = foreach_delete_current(options, lc);
+			break;
+		}
+		else if (strcmp(def->defname, "program") == 0)
+		{
+			*filename = defGetString(def);
+			*is_program = true;
+			options = foreach_delete_current(options, lc);
+			break;
+		}
+	}
+
+	/*
+	 * The validator should have checked that filename or program was included
+	 * in the options, but check again, just in case.
+	 */
+	if (*filename == NULL)
+		elog(ERROR, "either filename or program is required for file_fdw foreign tables");
+
+	*other_options = options;
+}
+
+/*
+ * Retrieve per-column generic options from pg_attribute and construct a list
+ * of DefElems representing them.
+ *
+ * At the moment we only have "force_not_null", and "force_null",
+ * which should each be combined into a single DefElem listing all such
+ * columns, since that's what COPY expects.
+ */
+static List *
+get_file_fdw_attribute_options(Oid relid)
+{
+	Relation	rel;
+	TupleDesc	tupleDesc;
+	AttrNumber	natts;
+	AttrNumber	attnum;
+	List	   *fnncolumns = NIL;
+	List	   *fncolumns = NIL;
+
+	List	   *options = NIL;
+
+	rel = table_open(relid, AccessShareLock);
+	tupleDesc = RelationGetDescr(rel);
+	natts = tupleDesc->natts;
+
+	/* Retrieve FDW options for all user-defined attributes. */
+	for (attnum = 1; attnum <= natts; attnum++)
+	{
+		Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum - 1);
+		List	   *options;
+		ListCell   *lc;
+
+		/* Skip dropped attributes. */
+		if (attr->attisdropped)
+			continue;
+
+		options = GetForeignColumnOptions(relid, attnum);
+		foreach(lc, options)
+		{
+			DefElem    *def = (DefElem *) lfirst(lc);
+
+			if (strcmp(def->defname, "force_not_null") == 0)
+			{
+				if (defGetBoolean(def))
+				{
+					char	   *attname = pstrdup(NameStr(attr->attname));
+
+					fnncolumns = lappend(fnncolumns, makeString(attname));
+				}
+			}
+			else if (strcmp(def->defname, "force_null") == 0)
+			{
+				if (defGetBoolean(def))
+				{
+					char	   *attname = pstrdup(NameStr(attr->attname));
+
+					fncolumns = lappend(fncolumns, makeString(attname));
+				}
+			}
+			/* maybe in future handle other options here */
+		}
+	}
+
+	table_close(rel, AccessShareLock);
+
+	/*
+	 * Return DefElem only when some column(s) have force_not_null /
+	 * force_null options set
+	 */
+	if (fnncolumns != NIL)
+		options = lappend(options, makeDefElem("force_not_null", (Node *) fnncolumns, -1));
+
+	if (fncolumns != NIL)
+		options = lappend(options, makeDefElem("force_null", (Node *) fncolumns, -1));
+
+	return options;
+}
+
+/*
+ * fileGetForeignRelSize
+ *		Obtain relation size estimates for a foreign table
+ */
+static void
+fileGetForeignRelSize(PlannerInfo *root,
+					  RelOptInfo *baserel,
+					  Oid foreigntableid)
+{
+	FileFdwPlanState *fdw_private;
+
+	/*
+	 * Fetch options.  We only need filename (or program) at this point, but
+	 * we might as well get everything and not need to re-fetch it later in
+	 * planning.
+	 */
+	fdw_private = (FileFdwPlanState *) palloc(sizeof(FileFdwPlanState));
+	fileGetOptions(foreigntableid,
+				   &fdw_private->filename,
+				   &fdw_private->is_program,
+				   &fdw_private->options);
+	baserel->fdw_private = (void *) fdw_private;
+
+	/* Estimate relation size */
+	estimate_size(root, baserel, fdw_private);
+}
+
+/*
+ * fileGetForeignPaths
+ *		Create possible access paths for a scan on the foreign table
+ *
+ *		Currently we don't support any push-down feature, so there is only one
+ *		possible access path, which simply returns all records in the order in
+ *		the data file.
+ */
+static void
+fileGetForeignPaths(PlannerInfo *root,
+					RelOptInfo *baserel,
+					Oid foreigntableid)
+{
+	FileFdwPlanState *fdw_private = (FileFdwPlanState *) baserel->fdw_private;
+	Cost		startup_cost;
+	Cost		total_cost;
+	List	   *columns;
+	List	   *coptions = NIL;
+
+	/* Decide whether to selectively perform binary conversion */
+	if (check_selective_binary_conversion(baserel,
+										  foreigntableid,
+										  &columns))
+		coptions = list_make1(makeDefElem("convert_selectively",
+										  (Node *) columns, -1));
+
+	/* Estimate costs */
+	estimate_costs(root, baserel, fdw_private,
+				   &startup_cost, &total_cost);
+
+	/*
+	 * Create a ForeignPath node and add it as only possible path.  We use the
+	 * fdw_private list of the path to carry the convert_selectively option;
+	 * it will be propagated into the fdw_private list of the Plan node.
+	 *
+	 * We don't support pushing join clauses into the quals of this path, but
+	 * it could still have required parameterization due to LATERAL refs in
+	 * its tlist.
+	 */
+	add_path(baserel, (Path *)
+			 create_foreignscan_path(root, baserel,
+									 NULL,	/* default pathtarget */
+									 baserel->rows,
+									 startup_cost,
+									 total_cost,
+									 NIL,	/* no pathkeys */
+									 baserel->lateral_relids,
+									 NULL,	/* no extra plan */
+									 coptions));
+
+	/*
+	 * If data file was sorted, and we knew it somehow, we could insert
+	 * appropriate pathkeys into the ForeignPath node to tell the planner
+	 * that.
+	 */
+}
+
+/*
+ * fileGetForeignPlan
+ *		Create a ForeignScan plan node for scanning the foreign table
+ */
+static ForeignScan *
+fileGetForeignPlan(PlannerInfo *root,
+				   RelOptInfo *baserel,
+				   Oid foreigntableid,
+				   ForeignPath *best_path,
+				   List *tlist,
+				   List *scan_clauses,
+				   Plan *outer_plan)
+{
+	Index		scan_relid = baserel->relid;
+
+	/*
+	 * We have no native ability to evaluate restriction clauses, so we just
+	 * put all the scan_clauses into the plan node's qual list for the
+	 * executor to check.  So all we have to do here is strip RestrictInfo
+	 * nodes from the clauses and ignore pseudoconstants (which will be
+	 * handled elsewhere).
+	 */
+	scan_clauses = extract_actual_clauses(scan_clauses, false);
+
+	/* Create the ForeignScan node */
+	return make_foreignscan(tlist,
+							scan_clauses,
+							scan_relid,
+							NIL,	/* no expressions to evaluate */
+							best_path->fdw_private,
+							NIL,	/* no custom tlist */
+							NIL,	/* no remote quals */
+							outer_plan);
+}
+
+/*
+ * fileExplainForeignScan
+ *		Produce extra output for EXPLAIN
+ */
+static void
+fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
+{
+	char	   *filename;
+	bool		is_program;
+	List	   *options;
+
+	/* Fetch options --- we only need filename and is_program at this point */
+	fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
+				   &filename, &is_program, &options);
+
+	if (is_program)
+		ExplainPropertyText("Foreign Program", filename, es);
+	else
+		ExplainPropertyText("Foreign File", filename, es);
+
+	/* Suppress file size if we're not showing cost details */
+	if (es->costs)
+	{
+		struct stat stat_buf;
+
+		if (!is_program &&
+			stat(filename, &stat_buf) == 0)
+			ExplainPropertyInteger("Foreign File Size", "b",
+								   (int64) stat_buf.st_size, es);
+	}
+}
+
+/*
+ * fileBeginForeignScan
+ *		Initiate access to the file by creating CopyState
+ */
+static void
+fileBeginForeignScan(ForeignScanState *node, int eflags)
+{
+	ForeignScan *plan = (ForeignScan *) node->ss.ps.plan;
+	char	   *filename;
+	bool		is_program;
+	List	   *options;
+	CopyFromState cstate;
+	FileFdwExecutionState *festate;
+
+	/*
+	 * Do nothing in EXPLAIN (no ANALYZE) case.  node->fdw_state stays NULL.
+	 */
+	if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
+		return;
+
+	/* Fetch options of foreign table */
+	fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
+				   &filename, &is_program, &options);
+
+	/* Add any options from the plan (currently only convert_selectively) */
+	options = list_concat(options, plan->fdw_private);
+
+	/*
+	 * Create CopyState from FDW options.  We always acquire all columns, so
+	 * as to match the expected ScanTupleSlot signature.
+	 */
+	cstate = BeginCopyFrom(NULL,
+						   node->ss.ss_currentRelation,
+						   NULL,
+						   filename,
+						   is_program,
+						   NULL,
+						   NIL,
+						   options);
+
+	/*
+	 * Save state in node->fdw_state.  We must save enough information to call
+	 * BeginCopyFrom() again.
+	 */
+	festate = (FileFdwExecutionState *) palloc(sizeof(FileFdwExecutionState));
+	festate->filename = filename;
+	festate->is_program = is_program;
+	festate->options = options;
+	festate->cstate = cstate;
+
+	node->fdw_state = (void *) festate;
+}
+
+/*
+ * fileIterateForeignScan
+ *		Read next record from the data file and store it into the
+ *		ScanTupleSlot as a virtual tuple
+ */
+static TupleTableSlot *
+fileIterateForeignScan(ForeignScanState *node)
+{
+	FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
+	TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
+	bool		found;
+	ErrorContextCallback errcallback;
+
+	/* Set up callback to identify error line number. */
+	errcallback.callback = CopyFromErrorCallback;
+	errcallback.arg = (void *) festate->cstate;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/*
+	 * The protocol for loading a virtual tuple into a slot is first
+	 * ExecClearTuple, then fill the values/isnull arrays, then
+	 * ExecStoreVirtualTuple.  If we don't find another row in the file, we
+	 * just skip the last step, leaving the slot empty as required.
+	 *
+	 * We can pass ExprContext = NULL because we read all columns from the
+	 * file, so no need to evaluate default expressions.
+	 */
+	ExecClearTuple(slot);
+	found = NextCopyFrom(festate->cstate, NULL,
+						 slot->tts_values, slot->tts_isnull);
+	if (found)
+		ExecStoreVirtualTuple(slot);
+
+	/* Remove error callback. */
+	error_context_stack = errcallback.previous;
+
+	return slot;
+}
+
+/*
+ * fileReScanForeignScan
+ *		Rescan table, possibly with new parameters
+ */
+static void
+fileReScanForeignScan(ForeignScanState *node)
+{
+	FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
+
+	EndCopyFrom(festate->cstate);
+
+	festate->cstate = BeginCopyFrom(NULL,
+									node->ss.ss_currentRelation,
+									NULL,
+									festate->filename,
+									festate->is_program,
+									NULL,
+									NIL,
+									festate->options);
+}
+
+/*
+ * fileEndForeignScan
+ *		Finish scanning foreign table and dispose objects used for this scan
+ */
+static void
+fileEndForeignScan(ForeignScanState *node)
+{
+	FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
+
+	/* if festate is NULL, we are in EXPLAIN; nothing to do */
+	if (festate)
+		EndCopyFrom(festate->cstate);
+}
+
+/*
+ * fileAnalyzeForeignTable
+ *		Test whether analyzing this foreign table is supported
+ */
+static bool
+fileAnalyzeForeignTable(Relation relation,
+						AcquireSampleRowsFunc *func,
+						BlockNumber *totalpages)
+{
+	char	   *filename;
+	bool		is_program;
+	List	   *options;
+	struct stat stat_buf;
+
+	/* Fetch options of foreign table */
+	fileGetOptions(RelationGetRelid(relation), &filename, &is_program, &options);
+
+	/*
+	 * If this is a program instead of a file, just return false to skip
+	 * analyzing the table.  We could run the program and collect stats on
+	 * whatever it currently returns, but it seems likely that in such cases
+	 * the output would be too volatile for the stats to be useful.  Maybe
+	 * there should be an option to enable doing this?
+	 */
+	if (is_program)
+		return false;
+
+	/*
+	 * Get size of the file.  (XXX if we fail here, would it be better to just
+	 * return false to skip analyzing the table?)
+	 */
+	if (stat(filename, &stat_buf) < 0)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not stat file \"%s\": %m",
+						filename)));
+
+	/*
+	 * Convert size to pages.  Must return at least 1 so that we can tell
+	 * later on that pg_class.relpages is not default.
+	 */
+	*totalpages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
+	if (*totalpages < 1)
+		*totalpages = 1;
+
+	*func = file_acquire_sample_rows;
+
+	return true;
+}
+
+/*
+ * fileIsForeignScanParallelSafe
+ *		Reading a file, or external program, in a parallel worker should work
+ *		just the same as reading it in the leader, so mark scans safe.
+ */
+static bool
+fileIsForeignScanParallelSafe(PlannerInfo *root, RelOptInfo *rel,
+							  RangeTblEntry *rte)
+{
+	return true;
+}
+
+/*
+ * check_selective_binary_conversion
+ *
+ * Check to see if it's useful to convert only a subset of the file's columns
+ * to binary.  If so, construct a list of the column names to be converted,
+ * return that at *columns, and return true.  (Note that it's possible to
+ * determine that no columns need be converted, for instance with a COUNT(*)
+ * query.  So we can't use returning a NIL list to indicate failure.)
+ */
+static bool
+check_selective_binary_conversion(RelOptInfo *baserel,
+								  Oid foreigntableid,
+								  List **columns)
+{
+	ForeignTable *table;
+	ListCell   *lc;
+	Relation	rel;
+	TupleDesc	tupleDesc;
+	AttrNumber	attnum;
+	Bitmapset  *attrs_used = NULL;
+	bool		has_wholerow = false;
+	int			numattrs;
+	int			i;
+
+	*columns = NIL;				/* default result */
+
+	/*
+	 * Check format of the file.  If binary format, this is irrelevant.
+	 */
+	table = GetForeignTable(foreigntableid);
+	foreach(lc, table->options)
+	{
+		DefElem    *def = (DefElem *) lfirst(lc);
+
+		if (strcmp(def->defname, "format") == 0)
+		{
+			char	   *format = defGetString(def);
+
+			if (strcmp(format, "binary") == 0)
+				return false;
+			break;
+		}
+	}
+
+	/* Collect all the attributes needed for joins or final output. */
+	pull_varattnos((Node *) baserel->reltarget->exprs, baserel->relid,
+				   &attrs_used);
+
+	/* Add all the attributes used by restriction clauses. */
+	foreach(lc, baserel->baserestrictinfo)
+	{
+		RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
+
+		pull_varattnos((Node *) rinfo->clause, baserel->relid,
+					   &attrs_used);
+	}
+
+	/* Convert attribute numbers to column names. */
+	rel = table_open(foreigntableid, AccessShareLock);
+	tupleDesc = RelationGetDescr(rel);
+
+	while ((attnum = bms_first_member(attrs_used)) >= 0)
+	{
+		/* Adjust for system attributes. */
+		attnum += FirstLowInvalidHeapAttributeNumber;
+
+		if (attnum == 0)
+		{
+			has_wholerow = true;
+			break;
+		}
+
+		/* Ignore system attributes. */
+		if (attnum < 0)
+			continue;
+
+		/* Get user attributes. */
+		if (attnum > 0)
+		{
+			Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum - 1);
+			char	   *attname = NameStr(attr->attname);
+
+			/* Skip dropped attributes (probably shouldn't see any here). */
+			if (attr->attisdropped)
+				continue;
+
+			/*
+			 * Skip generated columns (COPY won't accept them in the column
+			 * list)
+			 */
+			if (attr->attgenerated)
+				continue;
+			*columns = lappend(*columns, makeString(pstrdup(attname)));
+		}
+	}
+
+	/* Count non-dropped user attributes while we have the tupdesc. */
+	numattrs = 0;
+	for (i = 0; i < tupleDesc->natts; i++)
+	{
+		Form_pg_attribute attr = TupleDescAttr(tupleDesc, i);
+
+		if (attr->attisdropped)
+			continue;
+		numattrs++;
+	}
+
+	table_close(rel, AccessShareLock);
+
+	/* If there's a whole-row reference, fail: we need all the columns. */
+	if (has_wholerow)
+	{
+		*columns = NIL;
+		return false;
+	}
+
+	/* If all the user attributes are needed, fail. */
+	if (numattrs == list_length(*columns))
+	{
+		*columns = NIL;
+		return false;
+	}
+
+	return true;
+}
+
+/*
+ * Estimate size of a foreign table.
+ *
+ * The main result is returned in baserel->rows.  We also set
+ * fdw_private->pages and fdw_private->ntuples for later use in the cost
+ * calculation.
+ */
+static void
+estimate_size(PlannerInfo *root, RelOptInfo *baserel,
+			  FileFdwPlanState *fdw_private)
+{
+	struct stat stat_buf;
+	BlockNumber pages;
+	double		ntuples;
+	double		nrows;
+
+	/*
+	 * Get size of the file.  It might not be there at plan time, though, in
+	 * which case we have to use a default estimate.  We also have to fall
+	 * back to the default if using a program as the input.
+	 */
+	if (fdw_private->is_program || stat(fdw_private->filename, &stat_buf) < 0)
+		stat_buf.st_size = 10 * BLCKSZ;
+
+	/*
+	 * Convert size to pages for use in I/O cost estimate later.
+	 */
+	pages = (stat_buf.st_size + (BLCKSZ - 1)) / BLCKSZ;
+	if (pages < 1)
+		pages = 1;
+	fdw_private->pages = pages;
+
+	/*
+	 * Estimate the number of tuples in the file.
+	 */
+	if (baserel->tuples >= 0 && baserel->pages > 0)
+	{
+		/*
+		 * We have # of pages and # of tuples from pg_class (that is, from a
+		 * previous ANALYZE), so compute a tuples-per-page estimate and scale
+		 * that by the current file size.
+		 */
+		double		density;
+
+		density = baserel->tuples / (double) baserel->pages;
+		ntuples = clamp_row_est(density * (double) pages);
+	}
+	else
+	{
+		/*
+		 * Otherwise we have to fake it.  We back into this estimate using the
+		 * planner's idea of the relation width; which is bogus if not all
+		 * columns are being read, not to mention that the text representation
+		 * of a row probably isn't the same size as its internal
+		 * representation.  Possibly we could do something better, but the
+		 * real answer to anyone who complains is "ANALYZE" ...
+		 */
+		int			tuple_width;
+
+		tuple_width = MAXALIGN(baserel->reltarget->width) +
+			MAXALIGN(SizeofHeapTupleHeader);
+		ntuples = clamp_row_est((double) stat_buf.st_size /
+								(double) tuple_width);
+	}
+	fdw_private->ntuples = ntuples;
+
+	/*
+	 * Now estimate the number of rows returned by the scan after applying the
+	 * baserestrictinfo quals.
+	 */
+	nrows = ntuples *
+		clauselist_selectivity(root,
+							   baserel->baserestrictinfo,
+							   0,
+							   JOIN_INNER,
+							   NULL);
+
+	nrows = clamp_row_est(nrows);
+
+	/* Save the output-rows estimate for the planner */
+	baserel->rows = nrows;
+}
+
+/*
+ * Estimate costs of scanning a foreign table.
+ *
+ * Results are returned in *startup_cost and *total_cost.
+ */
+static void
+estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+			   FileFdwPlanState *fdw_private,
+			   Cost *startup_cost, Cost *total_cost)
+{
+	BlockNumber pages = fdw_private->pages;
+	double		ntuples = fdw_private->ntuples;
+	Cost		run_cost = 0;
+	Cost		cpu_per_tuple;
+
+	/*
+	 * We estimate costs almost the same way as cost_seqscan(), thus assuming
+	 * that I/O costs are equivalent to a regular table file of the same size.
+	 * However, we take per-tuple CPU costs as 10x of a seqscan, to account
+	 * for the cost of parsing records.
+	 *
+	 * In the case of a program source, this calculation is even more divorced
+	 * from reality, but we have no good alternative; and it's not clear that
+	 * the numbers we produce here matter much anyway, since there's only one
+	 * access path for the rel.
+	 */
+	run_cost += seq_page_cost * pages;
+
+	*startup_cost = baserel->baserestrictcost.startup;
+	cpu_per_tuple = cpu_tuple_cost * 10 + baserel->baserestrictcost.per_tuple;
+	run_cost += cpu_per_tuple * ntuples;
+	*total_cost = *startup_cost + run_cost;
+}
+
+/*
+ * file_acquire_sample_rows -- acquire a random sample of rows from the table
+ *
+ * Selected rows are returned in the caller-allocated array rows[],
+ * which must have at least targrows entries.
+ * The actual number of rows selected is returned as the function result.
+ * We also count the total number of rows in the file and return it into
+ * *totalrows.  Note that *totaldeadrows is always set to 0.
+ *
+ * Note that the returned list of rows is not always in order by physical
+ * position in the file.  Therefore, correlation estimates derived later
+ * may be meaningless, but it's OK because we don't use the estimates
+ * currently (the planner only pays attention to correlation for indexscans).
+ */
+static int
+file_acquire_sample_rows(Relation onerel, int elevel,
+						 HeapTuple *rows, int targrows,
+						 double *totalrows, double *totaldeadrows)
+{
+	int			numrows = 0;
+	double		rowstoskip = -1;	/* -1 means not set yet */
+	ReservoirStateData rstate;
+	TupleDesc	tupDesc;
+	Datum	   *values;
+	bool	   *nulls;
+	bool		found;
+	char	   *filename;
+	bool		is_program;
+	List	   *options;
+	CopyFromState cstate;
+	ErrorContextCallback errcallback;
+	MemoryContext oldcontext = CurrentMemoryContext;
+	MemoryContext tupcontext;
+
+	Assert(onerel);
+	Assert(targrows > 0);
+
+	tupDesc = RelationGetDescr(onerel);
+	values = (Datum *) palloc(tupDesc->natts * sizeof(Datum));
+	nulls = (bool *) palloc(tupDesc->natts * sizeof(bool));
+
+	/* Fetch options of foreign table */
+	fileGetOptions(RelationGetRelid(onerel), &filename, &is_program, &options);
+
+	/*
+	 * Create CopyState from FDW options.
+	 */
+	cstate = BeginCopyFrom(NULL, onerel, NULL, filename, is_program, NULL, NIL,
+						   options);
+
+	/*
+	 * Use per-tuple memory context to prevent leak of memory used to read
+	 * rows from the file with Copy routines.
+	 */
+	tupcontext = AllocSetContextCreate(CurrentMemoryContext,
+									   "file_fdw temporary context",
+									   ALLOCSET_DEFAULT_SIZES);
+
+	/* Prepare for sampling rows */
+	reservoir_init_selection_state(&rstate, targrows);
+
+	/* Set up callback to identify error line number. */
+	errcallback.callback = CopyFromErrorCallback;
+	errcallback.arg = (void *) cstate;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	*totalrows = 0;
+	*totaldeadrows = 0;
+	for (;;)
+	{
+		/* Check for user-requested abort or sleep */
+		vacuum_delay_point();
+
+		/* Fetch next row */
+		MemoryContextReset(tupcontext);
+		MemoryContextSwitchTo(tupcontext);
+
+		found = NextCopyFrom(cstate, NULL, values, nulls);
+
+		MemoryContextSwitchTo(oldcontext);
+
+		if (!found)
+			break;
+
+		/*
+		 * The first targrows sample rows are simply copied into the
+		 * reservoir.  Then we start replacing tuples in the sample until we
+		 * reach the end of the relation. This algorithm is from Jeff Vitter's
+		 * paper (see more info in commands/analyze.c).
+		 */
+		if (numrows < targrows)
+		{
+			rows[numrows++] = heap_form_tuple(tupDesc, values, nulls);
+		}
+		else
+		{
+			/*
+			 * t in Vitter's paper is the number of records already processed.
+			 * If we need to compute a new S value, we must use the
+			 * not-yet-incremented value of totalrows as t.
+			 */
+			if (rowstoskip < 0)
+				rowstoskip = reservoir_get_next_S(&rstate, *totalrows, targrows);
+
+			if (rowstoskip <= 0)
+			{
+				/*
+				 * Found a suitable tuple, so save it, replacing one old tuple
+				 * at random
+				 */
+				int			k = (int) (targrows * sampler_random_fract(rstate.randstate));
+
+				Assert(k >= 0 && k < targrows);
+				heap_freetuple(rows[k]);
+				rows[k] = heap_form_tuple(tupDesc, values, nulls);
+			}
+
+			rowstoskip -= 1;
+		}
+
+		*totalrows += 1;
+	}
+
+	/* Remove error callback. */
+	error_context_stack = errcallback.previous;
+
+	/* Clean up. */
+	MemoryContextDelete(tupcontext);
+
+	EndCopyFrom(cstate);
+
+	pfree(values);
+	pfree(nulls);
+
+	/*
+	 * Emit some interesting relation info
+	 */
+	ereport(elevel,
+			(errmsg("\"%s\": file contains %.0f rows; "
+					"%d rows in sample",
+					RelationGetRelationName(onerel),
+					*totalrows, numrows)));
+
+	return numrows;
+}