Add contrib/file_fdw foreign-data wrapper for reading files via COPY.

This is both very useful in its own right, and an important test case for the core FDW support. This commit includes a small refactoring of copy.c to expose its option checking code as a separately callable function. The original patch submission duplicated hundreds of lines of that code, which seemed pretty unmaintainable. Shigeru Hanada, reviewed by Itagaki Takahiro and Tom Lane
2025-03-19 20:00:51 +08:00 · 2011-02-20 14:06:59 -05:00 · 2011-02-20 14:06:59 -05:00 · 7c5d0ae707
commit 7c5d0ae707
parent bb74240794
19 changed files with 1171 additions and 55 deletions
--- a/contrib/Makefile
+++ b/contrib/Makefile
@ -18,6 +18,7 @@ SUBDIRS = \
 		dict_xsyn	\
 		dummy_seclabel	\
 		earthdistance	\
+		file_fdw	\
 		fuzzystrmatch	\
 		hstore		\
 		intagg		\
--- a/contrib/README
+++ b/contrib/README
@ -73,6 +73,10 @@ earthdistance -
 	Functions for computing distances between two points on Earth
 	by Bruno Wolff III <bruno@wolff.to> and Hal Snyder <hal@vailsys.com>

+file_fdw
+	Foreign-data wrapper for server-side CSV/TEXT files
+	by Shigeru Hanada <hanada@metrosystems.co.jp>
+
 fuzzystrmatch -
 	Levenshtein, metaphone, and soundex fuzzy string matching
 	by Joe Conway <mail@joeconway.com> and Joel Burton <jburton@scw.org>
--- a/contrib/file_fdw/.gitignore
+++ b/contrib/file_fdw/.gitignore
@ -0,0 +1,2 @@
+# Generated subdirectories
+/results/
--- a/contrib/file_fdw/Makefile
+++ b/contrib/file_fdw/Makefile
@ -0,0 +1,21 @@
+# contrib/file_fdw/Makefile
+
+MODULES = file_fdw
+
+EXTENSION = file_fdw
+DATA = file_fdw--1.0.sql
+
+REGRESS = file_fdw
+
+EXTRA_CLEAN = sql/file_fdw.sql expected/file_fdw.out
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = contrib/file_fdw
+top_builddir = ../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
--- a/contrib/file_fdw/data/agg.bad
+++ b/contrib/file_fdw/data/agg.bad
@ -0,0 +1,4 @@
+56;@7.8@
+100;@99.097@
+0;@aaa@
+42;@324.78@
--- a/contrib/file_fdw/data/agg.csv
+++ b/contrib/file_fdw/data/agg.csv
@ -0,0 +1,4 @@
+56;@7.8@
+100;@99.097@
+0;@0.09561@
+42;@324.78@
--- a/contrib/file_fdw/data/agg.data
+++ b/contrib/file_fdw/data/agg.data
@ -0,0 +1,4 @@
+56	7.8
+100	99.097
+0	0.09561
+42	324.78
--- a/contrib/file_fdw/expected/.gitignore
+++ b/contrib/file_fdw/expected/.gitignore
@ -0,0 +1 @@
+/file_fdw.out
--- a/contrib/file_fdw/file_fdw--1.0.sql
+++ b/contrib/file_fdw/file_fdw--1.0.sql
@ -0,0 +1,15 @@
+/* contrib/file_fdw/file_fdw--1.0.sql */
+
+CREATE FUNCTION file_fdw_handler()
+RETURNS fdw_handler
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FUNCTION file_fdw_validator(text[], oid)
+RETURNS void
+AS 'MODULE_PATHNAME'
+LANGUAGE C STRICT;
+
+CREATE FOREIGN DATA WRAPPER file_fdw
+  HANDLER file_fdw_handler
+  VALIDATOR file_fdw_validator;
--- a/contrib/file_fdw/file_fdw.c
+++ b/contrib/file_fdw/file_fdw.c
@ -0,0 +1,536 @@
+/*-------------------------------------------------------------------------
+ *
+ * file_fdw.c
+ *		  foreign-data wrapper for server-side flat files.
+ *
+ * Copyright (c) 2010-2011, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		  contrib/file_fdw/file_fdw.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <sys/stat.h>
+#include <unistd.h>
+
+#include "access/reloptions.h"
+#include "catalog/pg_foreign_table.h"
+#include "commands/copy.h"
+#include "commands/defrem.h"
+#include "commands/explain.h"
+#include "foreign/fdwapi.h"
+#include "foreign/foreign.h"
+#include "miscadmin.h"
+#include "optimizer/cost.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 COPY FROM command.
+ *
+ * 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 struct FileFdwOption valid_options[] = {
+	/* File options */
+	{ "filename",		ForeignTableRelationId },
+
+	/* Format options */
+	/* oids option is not supported */
+	{ "format",			ForeignTableRelationId },
+	{ "header",			ForeignTableRelationId },
+	{ "delimiter",		ForeignTableRelationId },
+	{ "quote",			ForeignTableRelationId },
+	{ "escape",			ForeignTableRelationId },
+	{ "null",			ForeignTableRelationId },
+
+	/*
+	 * force_quote is not supported by file_fdw because it's for COPY TO.
+	 */
+
+	/*
+	 * force_not_null is not supported by file_fdw.  It would need a parser
+	 * for list of columns, not to mention a way to check the column list
+	 * against the table.
+	 */
+
+	/* Sentinel */
+	{ NULL,			InvalidOid }
+};
+
+/*
+ * FDW-specific information for ForeignScanState.fdw_state.
+ */
+typedef struct FileFdwExecutionState
+{
+	char		   *filename;	/* file to read */
+	List		   *options;	/* merged COPY options, excluding filename */
+	CopyState		cstate;		/* state of reading file */
+} FileFdwExecutionState;
+
+/*
+ * SQL functions
+ */
+extern Datum file_fdw_handler(PG_FUNCTION_ARGS);
+extern Datum file_fdw_validator(PG_FUNCTION_ARGS);
+
+PG_FUNCTION_INFO_V1(file_fdw_handler);
+PG_FUNCTION_INFO_V1(file_fdw_validator);
+
+/*
+ * FDW callback routines
+ */
+static FdwPlan *filePlanForeignScan(Oid foreigntableid,
+									PlannerInfo *root,
+									RelOptInfo *baserel);
+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);
+
+/*
+ * Helper functions
+ */
+static bool is_valid_option(const char *option, Oid context);
+static void fileGetOptions(Oid foreigntableid,
+			   char **filename, List **other_options);
+static void estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+						   const char *filename,
+						   Cost *startup_cost, Cost *total_cost);
+
+
+/*
+ * 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->PlanForeignScan = filePlanForeignScan;
+	fdwroutine->ExplainForeignScan = fileExplainForeignScan;
+	fdwroutine->BeginForeignScan = fileBeginForeignScan;
+	fdwroutine->IterateForeignScan = fileIterateForeignScan;
+	fdwroutine->ReScanForeignScan = fileReScanForeignScan;
+	fdwroutine->EndForeignScan = fileEndForeignScan;
+
+	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;
+	List	   *other_options = NIL;
+	ListCell   *cell;
+
+	/*
+	 * Only superusers are allowed to set options of a file_fdw foreign table.
+	 * This is because the filename is one of those options, and we don't
+	 * want non-superusers to be able to determine which file gets read.
+	 *
+	 * 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 at
+	 * any options level other than foreign table --- otherwise there'd
+	 * still be a security hole.
+	 */
+	if (catalog == ForeignTableRelationId && !superuser())
+		ereport(ERROR,
+				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+				 errmsg("only superuser can change options of a file_fdw foreign table")));
+
+	/*
+	 * 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))
+		{
+			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),
+					 errhint("Valid options in this context are: %s",
+							 buf.data)));
+		}
+
+		/* Separate out filename, since ProcessCopyOptions won't allow it */
+		if (strcmp(def->defname, "filename") == 0)
+		{
+			if (filename)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			filename = defGetString(def);
+		}
+		else
+			other_options = lappend(other_options, def);
+	}
+
+	/*
+	 * Now apply the core COPY code's validation logic for more checks.
+	 */
+	ProcessCopyOptions(NULL, true, other_options);
+
+	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)
+{
+	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" from the other options because
+ * it must not appear in the options list passed to the core COPY code.
+ */
+static void
+fileGetOptions(Oid foreigntableid,
+			   char **filename, List **other_options)
+{
+	ForeignTable *table;
+	ForeignServer *server;
+	ForeignDataWrapper *wrapper;
+	List	   *options;
+	ListCell   *lc,
+			   *prev;
+
+	/*
+	 * 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);
+
+	/*
+	 * Separate out the filename.
+	 */
+	*filename = NULL;
+	prev = NULL;
+	foreach(lc, options)
+	{
+		DefElem	   *def = (DefElem *) lfirst(lc);
+
+		if (strcmp(def->defname, "filename") == 0)
+		{
+			*filename = defGetString(def);
+			options = list_delete_cell(options, lc, prev);
+			break;
+		}
+		prev = lc;
+	}
+	if (*filename == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_FDW_UNABLE_TO_CREATE_REPLY),
+				 errmsg("filename is required for file_fdw foreign tables")));
+	*other_options = options;
+}
+
+/*
+ * filePlanForeignScan
+ *		Create a FdwPlan for a scan on the foreign table
+ */
+static FdwPlan *
+filePlanForeignScan(Oid foreigntableid,
+					PlannerInfo *root,
+					RelOptInfo *baserel)
+{
+	FdwPlan	   *fdwplan;
+	char	   *filename;
+	List	   *options;
+
+	/* Fetch options --- we only need filename at this point */
+	fileGetOptions(foreigntableid, &filename, &options);
+
+	/* Construct FdwPlan with cost estimates */
+	fdwplan = makeNode(FdwPlan);
+	estimate_costs(root, baserel, filename,
+				   &fdwplan->startup_cost, &fdwplan->total_cost);
+	fdwplan->fdw_private = NIL;				/* not used */
+
+	return fdwplan;
+}
+
+/*
+ * fileExplainForeignScan
+ *		Produce extra output for EXPLAIN
+ */
+static void
+fileExplainForeignScan(ForeignScanState *node, ExplainState *es)
+{
+	char	   *filename;
+	List	   *options;
+
+	/* Fetch options --- we only need filename at this point */
+	fileGetOptions(RelationGetRelid(node->ss.ss_currentRelation),
+				   &filename, &options);
+
+	ExplainPropertyText("Foreign File", filename, es);
+
+	/* Suppress file size if we're not showing cost details */
+	if (es->costs)
+	{
+		struct stat		stat_buf;
+
+		if (stat(filename, &stat_buf) == 0)
+			ExplainPropertyLong("Foreign File Size", (long) stat_buf.st_size,
+								es);
+	}
+}
+
+/*
+ * fileBeginForeignScan
+ *		Initiate access to the file by creating CopyState
+ */
+static void
+fileBeginForeignScan(ForeignScanState *node, int eflags)
+{
+	char	   *filename;
+	List	   *options;
+	CopyState	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, &options);
+
+	/*
+	 * Create CopyState from FDW options.  We always acquire all columns,
+	 * so as to match the expected ScanTupleSlot signature.
+	 */
+	cstate = BeginCopyFrom(node->ss.ss_currentRelation,
+						   filename,
+						   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->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 errcontext;
+
+	/* Set up callback to identify error line number. */
+	errcontext.callback = CopyFromErrorCallback;
+	errcontext.arg = (void *) festate->cstate;
+	errcontext.previous = error_context_stack;
+	error_context_stack = &errcontext;
+
+	/*
+	 * 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.
+	 *
+	 * We can also pass tupleOid = NULL because we don't allow oids for
+	 * foreign tables.
+	 */
+	ExecClearTuple(slot);
+	found = NextCopyFrom(festate->cstate, NULL,
+						 slot->tts_values, slot->tts_isnull,
+						 NULL);
+	if (found)
+		ExecStoreVirtualTuple(slot);
+
+	/* Remove error callback. */
+	error_context_stack = errcontext.previous;
+
+	return slot;
+}
+
+/*
+ * 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);
+}
+
+/*
+ * fileReScanForeignScan
+ *		Rescan table, possibly with new parameters
+ */
+static void
+fileReScanForeignScan(ForeignScanState *node)
+{
+	FileFdwExecutionState *festate = (FileFdwExecutionState *) node->fdw_state;
+
+	EndCopyFrom(festate->cstate);
+
+	festate->cstate = BeginCopyFrom(node->ss.ss_currentRelation,
+									festate->filename,
+									NIL,
+									festate->options);
+}
+
+/*
+ * Estimate costs of scanning a foreign table.
+ */
+static void
+estimate_costs(PlannerInfo *root, RelOptInfo *baserel,
+			   const char *filename,
+			   Cost *startup_cost, Cost *total_cost)
+{
+	struct stat		stat_buf;
+	BlockNumber		pages;
+	int				tuple_width;
+	double			ntuples;
+	double			nrows;
+	Cost			run_cost = 0;
+	Cost			cpu_per_tuple;
+
+	/*
+	 * Get size of the file.  It might not be there at plan time, though,
+	 * in which case we have to use a default estimate.
+	 */
+	if (stat(filename, &stat_buf) < 0)
+		stat_buf.st_size = 10 * BLCKSZ;
+
+	/*
+	 * Convert size to pages for use in I/O cost estimate below.
+	 */
+	pages = (stat_buf.st_size + (BLCKSZ-1)) / BLCKSZ;
+	if (pages < 1)
+		pages = 1;
+
+	/*
+	 * Estimate the number of tuples in the file.  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.
+	 * FIXME later.
+	 */
+	tuple_width = MAXALIGN(baserel->width) + MAXALIGN(sizeof(HeapTupleHeaderData));
+
+	ntuples = clamp_row_est((double) stat_buf.st_size / (double) tuple_width);
+
+	/*
+	 * Now estimate the number of rows returned by the scan after applying
+	 * the baserestrictinfo quals.  This is pretty bogus too, since the
+	 * planner will have no stats about the relation, but it's better than
+	 * nothing.
+	 */
+	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;
+
+	/*
+	 * Now estimate costs.  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.
+	 */
+	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;
+}
--- a/contrib/file_fdw/file_fdw.control
+++ b/contrib/file_fdw/file_fdw.control
@ -0,0 +1,5 @@
+# file_fdw extension
+comment = 'foreign-data wrapper for flat file access'
+default_version = '1.0'
+module_pathname = '$libdir/file_fdw'
+relocatable = true
--- a/contrib/file_fdw/input/file_fdw.source
+++ b/contrib/file_fdw/input/file_fdw.source
@ -0,0 +1,131 @@
+--
+-- Test foreign-data wrapper file_fdw.
+--
+
+-- Clean up in case a prior regression run failed
+SET client_min_messages TO 'error';
+DROP ROLE IF EXISTS file_fdw_superuser, file_fdw_user, no_priv_user;
+RESET client_min_messages;
+
+CREATE ROLE file_fdw_superuser LOGIN SUPERUSER; -- is a superuser
+CREATE ROLE file_fdw_user LOGIN;                -- has priv and user mapping
+CREATE ROLE no_priv_user LOGIN;                 -- has priv but no user mapping
+
+-- Install file_fdw
+CREATE EXTENSION file_fdw;
+
+-- file_fdw_superuser owns fdw-related objects
+SET ROLE file_fdw_superuser;
+CREATE SERVER file_server FOREIGN DATA WRAPPER file_fdw;
+
+-- privilege tests
+SET ROLE file_fdw_user;
+CREATE FOREIGN DATA WRAPPER file_fdw2 HANDLER file_fdw_handler VALIDATOR file_fdw_validator;   -- ERROR
+CREATE SERVER file_server2 FOREIGN DATA WRAPPER file_fdw;   -- ERROR
+CREATE USER MAPPING FOR file_fdw_user SERVER file_server;   -- ERROR
+
+SET ROLE file_fdw_superuser;
+GRANT USAGE ON FOREIGN SERVER file_server TO file_fdw_user;
+
+SET ROLE file_fdw_user;
+CREATE USER MAPPING FOR file_fdw_user SERVER file_server;
+
+-- create user mappings and grant privilege to test users
+SET ROLE file_fdw_superuser;
+CREATE USER MAPPING FOR file_fdw_superuser SERVER file_server;
+CREATE USER MAPPING FOR no_priv_user SERVER file_server;
+
+-- validator tests
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'xml');  -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', header 'true');      -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', quote ':');          -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', escape ':');         -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'binary', header 'true');    -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'binary', quote ':');        -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'binary', escape ':');       -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter 'a');      -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', escape '-');         -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', quote '-', null '=-=');   -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '-', null '=-=');    -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '-', quote '-');    -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '---');     -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', quote '---');         -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', escape '---');        -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter '\');       -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter '.');       -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter '1');       -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter 'a');       -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '
+');       -- ERROR
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', null '
+');       -- ERROR
+
+CREATE FOREIGN TABLE agg_text (
+	a	int2,
+	b	float4
+) SERVER file_server
+OPTIONS (format 'text', filename '@abs_srcdir@/data/agg.data', delimiter '	', null '\N');
+GRANT SELECT ON agg_text TO file_fdw_user;
+CREATE FOREIGN TABLE agg_csv (
+	a	int2,
+	b	float4
+) SERVER file_server
+OPTIONS (format 'csv', filename '@abs_srcdir@/data/agg.csv', header 'true', delimiter ';', quote '@', escape '"', null '');
+CREATE FOREIGN TABLE agg_bad (
+	a	int2,
+	b	float4
+) SERVER file_server
+OPTIONS (format 'csv', filename '@abs_srcdir@/data/agg.bad', header 'true', delimiter ';', quote '@', escape '"', null '');
+
+-- basic query tests
+SELECT * FROM agg_text WHERE b > 10.0 ORDER BY a;
+SELECT * FROM agg_csv ORDER BY a;
+SELECT * FROM agg_csv c JOIN agg_text t ON (t.a = c.a) ORDER BY c.a;
+
+-- error context report tests
+SELECT * FROM agg_bad;               -- ERROR
+
+-- misc query tests
+\t on
+EXPLAIN (VERBOSE, COSTS FALSE) SELECT * FROM agg_csv;
+\t off
+PREPARE st(int) AS SELECT * FROM agg_csv WHERE a = $1;
+EXECUTE st(100);
+EXECUTE st(100);
+DEALLOCATE st;
+
+-- tableoid
+SELECT tableoid::regclass, b FROM agg_csv;
+
+-- updates aren't supported
+INSERT INTO agg_csv VALUES(1,2.0);
+UPDATE agg_csv SET a = 1;
+DELETE FROM agg_csv WHERE a = 100;
+SELECT * FROM agg_csv FOR UPDATE OF agg_csv;
+-- but this should be ignored
+SELECT * FROM agg_csv FOR UPDATE;
+
+-- privilege tests
+SET ROLE file_fdw_superuser;
+SELECT * FROM agg_text ORDER BY a;
+SET ROLE file_fdw_user;
+SELECT * FROM agg_text ORDER BY a;
+SET ROLE no_priv_user;
+SELECT * FROM agg_text ORDER BY a;   -- ERROR
+SET ROLE file_fdw_user;
+\t on
+EXPLAIN (VERBOSE, COSTS FALSE) SELECT * FROM agg_text WHERE a > 0;
+\t off
+
+-- privilege tests for object
+SET ROLE file_fdw_superuser;
+ALTER FOREIGN TABLE agg_text OWNER TO file_fdw_user;
+ALTER FOREIGN TABLE agg_text OPTIONS (SET format 'text');
+SET ROLE file_fdw_user;
+ALTER FOREIGN TABLE agg_text OPTIONS (SET format 'text');
+SET ROLE file_fdw_superuser;
+
+-- cleanup
+RESET ROLE;
+DROP EXTENSION file_fdw CASCADE;
+DROP ROLE file_fdw_superuser, file_fdw_user, no_priv_user;
--- a/contrib/file_fdw/output/file_fdw.source
+++ b/contrib/file_fdw/output/file_fdw.source
@ -0,0 +1,225 @@
+--
+-- Test foreign-data wrapper file_fdw.
+--
+-- Clean up in case a prior regression run failed
+SET client_min_messages TO 'error';
+DROP ROLE IF EXISTS file_fdw_superuser, file_fdw_user, no_priv_user;
+RESET client_min_messages;
+CREATE ROLE file_fdw_superuser LOGIN SUPERUSER; -- is a superuser
+CREATE ROLE file_fdw_user LOGIN;                -- has priv and user mapping
+CREATE ROLE no_priv_user LOGIN;                 -- has priv but no user mapping
+-- Install file_fdw
+CREATE EXTENSION file_fdw;
+-- file_fdw_superuser owns fdw-related objects
+SET ROLE file_fdw_superuser;
+CREATE SERVER file_server FOREIGN DATA WRAPPER file_fdw;
+-- privilege tests
+SET ROLE file_fdw_user;
+CREATE FOREIGN DATA WRAPPER file_fdw2 HANDLER file_fdw_handler VALIDATOR file_fdw_validator;   -- ERROR
+ERROR:  permission denied to create foreign-data wrapper "file_fdw2"
+HINT:  Must be superuser to create a foreign-data wrapper.
+CREATE SERVER file_server2 FOREIGN DATA WRAPPER file_fdw;   -- ERROR
+ERROR:  permission denied for foreign-data wrapper file_fdw
+CREATE USER MAPPING FOR file_fdw_user SERVER file_server;   -- ERROR
+ERROR:  permission denied for foreign server file_server
+SET ROLE file_fdw_superuser;
+GRANT USAGE ON FOREIGN SERVER file_server TO file_fdw_user;
+SET ROLE file_fdw_user;
+CREATE USER MAPPING FOR file_fdw_user SERVER file_server;
+-- create user mappings and grant privilege to test users
+SET ROLE file_fdw_superuser;
+CREATE USER MAPPING FOR file_fdw_superuser SERVER file_server;
+CREATE USER MAPPING FOR no_priv_user SERVER file_server;
+-- validator tests
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'xml');  -- ERROR
+ERROR:  COPY format "xml" not recognized
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', header 'true');      -- ERROR
+ERROR:  COPY HEADER available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', quote ':');          -- ERROR
+ERROR:  COPY quote available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', escape ':');         -- ERROR
+ERROR:  COPY escape available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'binary', header 'true');    -- ERROR
+ERROR:  COPY HEADER available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'binary', quote ':');        -- ERROR
+ERROR:  COPY quote available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'binary', escape ':');       -- ERROR
+ERROR:  COPY escape available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter 'a');      -- ERROR
+ERROR:  COPY delimiter cannot be "a"
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', escape '-');         -- ERROR
+ERROR:  COPY escape available only in CSV mode
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', quote '-', null '=-=');   -- ERROR
+ERROR:  CSV quote character must not appear in the NULL specification
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '-', null '=-=');    -- ERROR
+ERROR:  COPY delimiter must not appear in the NULL specification
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '-', quote '-');    -- ERROR
+ERROR:  COPY delimiter and quote must be different
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '---');     -- ERROR
+ERROR:  COPY delimiter must be a single one-byte character
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', quote '---');         -- ERROR
+ERROR:  COPY quote must be a single one-byte character
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', escape '---');        -- ERROR
+ERROR:  COPY escape must be a single one-byte character
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter '\');       -- ERROR
+ERROR:  COPY delimiter cannot be "\"
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter '.');       -- ERROR
+ERROR:  COPY delimiter cannot be "."
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter '1');       -- ERROR
+ERROR:  COPY delimiter cannot be "1"
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'text', delimiter 'a');       -- ERROR
+ERROR:  COPY delimiter cannot be "a"
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', delimiter '
+');       -- ERROR
+ERROR:  COPY delimiter cannot be newline or carriage return
+CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (format 'csv', null '
+');       -- ERROR
+ERROR:  COPY null representation cannot use newline or carriage return
+CREATE FOREIGN TABLE agg_text (
+	a	int2,
+	b	float4
+) SERVER file_server
+OPTIONS (format 'text', filename '@abs_srcdir@/data/agg.data', delimiter '	', null '\N');
+GRANT SELECT ON agg_text TO file_fdw_user;
+CREATE FOREIGN TABLE agg_csv (
+	a	int2,
+	b	float4
+) SERVER file_server
+OPTIONS (format 'csv', filename '@abs_srcdir@/data/agg.csv', header 'true', delimiter ';', quote '@', escape '"', null '');
+CREATE FOREIGN TABLE agg_bad (
+	a	int2,
+	b	float4
+) SERVER file_server
+OPTIONS (format 'csv', filename '@abs_srcdir@/data/agg.bad', header 'true', delimiter ';', quote '@', escape '"', null '');
+-- basic query tests
+SELECT * FROM agg_text WHERE b > 10.0 ORDER BY a;
+  a  |   b    
+-----+--------
+  42 | 324.78
+ 100 | 99.097
+(2 rows)
+
+SELECT * FROM agg_csv ORDER BY a;
+  a  |    b    
+-----+---------
+   0 | 0.09561
+  42 |  324.78
+ 100 |  99.097
+(3 rows)
+
+SELECT * FROM agg_csv c JOIN agg_text t ON (t.a = c.a) ORDER BY c.a;
+  a  |    b    |  a  |    b    
+-----+---------+-----+---------
+   0 | 0.09561 |   0 | 0.09561
+  42 |  324.78 |  42 |  324.78
+ 100 |  99.097 | 100 |  99.097
+(3 rows)
+
+-- error context report tests
+SELECT * FROM agg_bad;               -- ERROR
+ERROR:  invalid input syntax for type real: "aaa"
+CONTEXT:  COPY agg_bad, line 3, column b: "aaa"
+-- misc query tests
+\t on
+EXPLAIN (VERBOSE, COSTS FALSE) SELECT * FROM agg_csv;
+ Foreign Scan on public.agg_csv
+   Output: a, b
+   Foreign File: @abs_srcdir@/data/agg.csv
+
+\t off
+PREPARE st(int) AS SELECT * FROM agg_csv WHERE a = $1;
+EXECUTE st(100);
+  a  |   b    
+-----+--------
+ 100 | 99.097
+(1 row)
+
+EXECUTE st(100);
+  a  |   b    
+-----+--------
+ 100 | 99.097
+(1 row)
+
+DEALLOCATE st;
+-- tableoid
+SELECT tableoid::regclass, b FROM agg_csv;
+ tableoid |    b    
+----------+---------
+ agg_csv  |  99.097
+ agg_csv  | 0.09561
+ agg_csv  |  324.78
+(3 rows)
+
+-- updates aren't supported
+INSERT INTO agg_csv VALUES(1,2.0);
+ERROR:  cannot change foreign table "agg_csv"
+UPDATE agg_csv SET a = 1;
+ERROR:  cannot change foreign table "agg_csv"
+DELETE FROM agg_csv WHERE a = 100;
+ERROR:  cannot change foreign table "agg_csv"
+SELECT * FROM agg_csv FOR UPDATE OF agg_csv;
+ERROR:  SELECT FOR UPDATE/SHARE cannot be used with foreign table "agg_csv"
+LINE 1: SELECT * FROM agg_csv FOR UPDATE OF agg_csv;
+                                            ^
+-- but this should be ignored
+SELECT * FROM agg_csv FOR UPDATE;
+  a  |    b    
+-----+---------
+ 100 |  99.097
+   0 | 0.09561
+  42 |  324.78
+(3 rows)
+
+-- privilege tests
+SET ROLE file_fdw_superuser;
+SELECT * FROM agg_text ORDER BY a;
+  a  |    b    
+-----+---------
+   0 | 0.09561
+  42 |  324.78
+  56 |     7.8
+ 100 |  99.097
+(4 rows)
+
+SET ROLE file_fdw_user;
+SELECT * FROM agg_text ORDER BY a;
+  a  |    b    
+-----+---------
+   0 | 0.09561
+  42 |  324.78
+  56 |     7.8
+ 100 |  99.097
+(4 rows)
+
+SET ROLE no_priv_user;
+SELECT * FROM agg_text ORDER BY a;   -- ERROR
+ERROR:  permission denied for relation agg_text
+SET ROLE file_fdw_user;
+\t on
+EXPLAIN (VERBOSE, COSTS FALSE) SELECT * FROM agg_text WHERE a > 0;
+ Foreign Scan on public.agg_text
+   Output: a, b
+   Filter: (agg_text.a > 0)
+   Foreign File: @abs_srcdir@/data/agg.data
+
+\t off
+-- privilege tests for object
+SET ROLE file_fdw_superuser;
+ALTER FOREIGN TABLE agg_text OWNER TO file_fdw_user;
+ALTER FOREIGN TABLE agg_text OPTIONS (SET format 'text');
+SET ROLE file_fdw_user;
+ALTER FOREIGN TABLE agg_text OPTIONS (SET format 'text');
+ERROR:  only superuser can change options of a file_fdw foreign table
+SET ROLE file_fdw_superuser;
+-- cleanup
+RESET ROLE;
+DROP EXTENSION file_fdw CASCADE;
+NOTICE:  drop cascades to 7 other objects
+DETAIL:  drop cascades to server file_server
+drop cascades to user mapping for file_fdw_user
+drop cascades to user mapping for file_fdw_superuser
+drop cascades to user mapping for no_priv_user
+drop cascades to foreign table agg_text
+drop cascades to foreign table agg_csv
+drop cascades to foreign table agg_bad
+DROP ROLE file_fdw_superuser, file_fdw_user, no_priv_user;
--- a/contrib/file_fdw/sql/.gitignore
+++ b/contrib/file_fdw/sql/.gitignore
@ -0,0 +1 @@
+/file_fdw.sql
--- a/doc/src/sgml/contrib.sgml
+++ b/doc/src/sgml/contrib.sgml
@ -100,6 +100,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
 &dict-xsyn;
 &dummy-seclabel;
 &earthdistance;
+ &file-fdw;
 &fuzzystrmatch;
 &hstore;
 &intagg;
--- a/doc/src/sgml/file-fdw.sgml
+++ b/doc/src/sgml/file-fdw.sgml
@ -0,0 +1,127 @@
+<!-- doc/src/sgml/file-fdw.sgml -->
+
+<sect1 id="file-fdw">
+ <title>file_fdw</title>
+
+ <indexterm zone="file-fdw">
+  <primary>file_fdw</primary>
+ </indexterm>
+
+ <para>
+  The <filename>file_fdw</> module provides the foreign-data wrapper
+  <function>file_fdw</function>, which can be used to access data
+  files in the server's filesystem.  Data files must be in a format
+  that can be read by <command>COPY FROM</command>;
+  see <xref linkend="sql-copy"> for details.
+ </para>
+
+ <para>
+  A foreign table created using this wrapper can have the following options:
+ </para>
+
+ <variablelist>
+
+  <varlistentry>
+   <term><literal>filename</literal></term>
+
+   <listitem>
+    <para>
+     Specifies the file to be read.  Required.  Must be an absolute path name.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>format</literal></term>
+
+   <listitem>
+    <para>
+     Specifies the file's format,
+     the same as <command>COPY</>'s <literal>FORMAT</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>header</literal></term>
+
+   <listitem>
+    <para>
+     Specifies whether the file has a header line,
+     the same as <command>COPY</>'s <literal>HEADER</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>delimiter</literal></term>
+
+   <listitem>
+    <para>
+     Specifies the file's delimiter character,
+     the same as <command>COPY</>'s <literal>DELIMITER</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>quote</literal></term>
+
+   <listitem>
+    <para>
+     Specifies the file's quote character,
+     the same as <command>COPY</>'s <literal>QUOTE</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>escape</literal></term>
+
+   <listitem>
+    <para>
+     Specifies the file's escape character,
+     the same as <command>COPY</>'s <literal>ESCAPE</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+  <varlistentry>
+   <term><literal>null</literal></term>
+
+   <listitem>
+    <para>
+     Specifies the file's null string,
+     the same as <command>COPY</>'s <literal>NULL</literal> option.
+    </para>
+   </listitem>
+  </varlistentry>
+
+ </variablelist>
+
+ <para>
+  <command>COPY</>'s <literal>OIDS</literal>, <literal>FORCE_QUOTE</literal>,
+  and <literal>FORCE_NOT_NULL</literal> options are currently not supported by
+  <literal>file_fdw</>.
+ </para>
+
+ <para>
+  These options can only be specified for a foreign table, not in the
+  options of the <literal>file_fdw</> foreign-data wrapper, nor in the
+  options of a server or user mapping using the wrapper.
+ </para>
+
+ <para>
+  Changing table-level options requires superuser privileges, for security
+  reasons: only a superuser should be able to determine which file is read.
+  In principle non-superusers could be allowed to change the other options,
+  but that's not supported at present.
+ </para>
+
+ <para>
+  For a foreign table using <literal>file_fdw</>, <command>EXPLAIN</> shows
+  the name of the file to be read.  Unless <literal>COSTS OFF</> is
+  specified, the file size (in bytes) is shown as well.
+ </para>
+
+</sect1>
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@ -106,6 +106,7 @@
 <!entity dict-xsyn       SYSTEM "dict-xsyn.sgml">
 <!entity dummy-seclabel  SYSTEM "dummy-seclabel.sgml">
 <!entity earthdistance   SYSTEM "earthdistance.sgml">
+<!entity file-fdw        SYSTEM "file-fdw.sgml">
 <!entity fuzzystrmatch   SYSTEM "fuzzystrmatch.sgml">
 <!entity hstore          SYSTEM "hstore.sgml">
 <!entity intagg          SYSTEM "intagg.sgml">
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@ -114,7 +114,10 @@ typedef struct CopyStateData
 	char	   *delim;			/* column delimiter (must be 1 byte) */
 	char	   *quote;			/* CSV quote char (must be 1 byte) */
 	char	   *escape;			/* CSV escape char (must be 1 byte) */
+	List	   *force_quote;	/* list of column names */
+	bool		force_quote_all; /* FORCE QUOTE *? */
 	bool	   *force_quote_flags;		/* per-column CSV FQ flags */
+	List	   *force_notnull;	/* list of column names */
 	bool	   *force_notnull_flags;	/* per-column CSV FNN flags */

 	/* these are just for error messages, see CopyFromErrorCallback */
@ -764,7 +767,7 @@ DoCopy(const CopyStmt *stmt, const char *queryString)

 		tupDesc = RelationGetDescr(rel);
 		attnums = CopyGetAttnums(tupDesc, rel, stmt->attlist);
-		foreach (cur, attnums)
+		foreach(cur, attnums)
 		{
 			int		attno = lfirst_int(cur) -
 							FirstLowInvalidHeapAttributeNumber;
@ -814,52 +817,33 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 }

 /*
- * Common setup routines used by BeginCopyFrom and BeginCopyTo.
+ * Process the statement option list for COPY.
 *
- * Iff <binary>, unload or reload in the binary format, as opposed to the
- * more wasteful but more robust and portable text format.
+ * Scan the options list (a list of DefElem) and transpose the information
+ * into cstate, applying appropriate error checking.
 *
- * Iff <oids>, unload or reload the format that includes OID information.
- * On input, we accept OIDs whether or not the table has an OID column,
- * but silently drop them if it does not.  On output, we report an error
- * if the user asks for OIDs in a table that has none (not providing an
- * OID column might seem friendlier, but could seriously confuse programs).
+ * cstate is assumed to be filled with zeroes initially.
 *
- * If in the text format, delimit columns with delimiter <delim> and print
- * NULL values as <null_print>.
+ * This is exported so that external users of the COPY API can sanity-check
+ * a list of options.  In that usage, cstate should be passed as NULL
+ * (since external users don't know sizeof(CopyStateData)) and the collected
+ * data is just leaked until CurrentMemoryContext is reset.
+ *
+ * Note that additional checking, such as whether column names listed in FORCE
+ * QUOTE actually exist, has to be applied later.  This just checks for
+ * self-consistency of the options list.
 */
-static CopyState
-BeginCopy(bool is_from,
-		  Relation rel,
-		  Node *raw_query,
-		  const char *queryString,
-		  List *attnamelist,
-		  List *options)
+void
+ProcessCopyOptions(CopyState cstate,
+				   bool is_from,
+				   List *options)
 {
-	CopyState	cstate;
-	List	   *force_quote = NIL;
-	List	   *force_notnull = NIL;
-	bool		force_quote_all = false;
 	bool		format_specified = false;
 	ListCell   *option;
-	TupleDesc	tupDesc;
-	int			num_phys_attrs;
-	MemoryContext oldcontext;

-	/* Allocate workspace and zero all fields */
-	cstate = (CopyStateData *) palloc0(sizeof(CopyStateData));
-
-	/*
-	 * We allocate everything used by a cstate in a new memory context.
-	 * This would avoid memory leaks repeated uses of COPY in a query.
-	 */
-	cstate->copycontext = AllocSetContextCreate(CurrentMemoryContext,
-												"COPY",
-												ALLOCSET_DEFAULT_MINSIZE,
-												ALLOCSET_DEFAULT_INITSIZE,
-												ALLOCSET_DEFAULT_MAXSIZE);
-
-	oldcontext = MemoryContextSwitchTo(cstate->copycontext);
+	/* Support external use for option sanity checking */
+	if (cstate == NULL)
+		cstate = (CopyStateData *) palloc0(sizeof(CopyStateData));

 	/* Extract options from the statement node tree */
 	foreach(option, options)
@ -936,14 +920,14 @@ BeginCopy(bool is_from,
 		}
 		else if (strcmp(defel->defname, "force_quote") == 0)
 		{
-			if (force_quote || force_quote_all)
+			if (cstate->force_quote || cstate->force_quote_all)
 				ereport(ERROR,
 						(errcode(ERRCODE_SYNTAX_ERROR),
 						 errmsg("conflicting or redundant options")));
 			if (defel->arg && IsA(defel->arg, A_Star))
-				force_quote_all = true;
+				cstate->force_quote_all = true;
 			else if (defel->arg && IsA(defel->arg, List))
-				force_quote = (List *) defel->arg;
+				cstate->force_quote = (List *) defel->arg;
 			else
 				ereport(ERROR,
 						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@ -952,12 +936,12 @@ BeginCopy(bool is_from,
 		}
 		else if (strcmp(defel->defname, "force_not_null") == 0)
 		{
-			if (force_notnull)
+			if (cstate->force_notnull)
 				ereport(ERROR,
 						(errcode(ERRCODE_SYNTAX_ERROR),
 						 errmsg("conflicting or redundant options")));
 			if (defel->arg && IsA(defel->arg, List))
-				force_notnull = (List *) defel->arg;
+				cstate->force_notnull = (List *) defel->arg;
 			else
 				ereport(ERROR,
 						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@ -1071,21 +1055,21 @@ BeginCopy(bool is_from,
 				 errmsg("COPY escape must be a single one-byte character")));

 	/* Check force_quote */
-	if (!cstate->csv_mode && (force_quote != NIL || force_quote_all))
+	if (!cstate->csv_mode && (cstate->force_quote || cstate->force_quote_all))
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("COPY force quote available only in CSV mode")));
-	if ((force_quote != NIL || force_quote_all) && is_from)
+	if ((cstate->force_quote || cstate->force_quote_all) && is_from)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("COPY force quote only available using COPY TO")));

 	/* Check force_notnull */
-	if (!cstate->csv_mode && force_notnull != NIL)
+	if (!cstate->csv_mode && cstate->force_notnull != NIL)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("COPY force not null available only in CSV mode")));
-	if (force_notnull != NIL && !is_from)
+	if (cstate->force_notnull != NIL && !is_from)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 			  errmsg("COPY force not null only available using COPY FROM")));
@ -1102,7 +1086,55 @@ BeginCopy(bool is_from,
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("CSV quote character must not appear in the NULL specification")));
+}

+/*
+ * Common setup routines used by BeginCopyFrom and BeginCopyTo.
+ *
+ * Iff <binary>, unload or reload in the binary format, as opposed to the
+ * more wasteful but more robust and portable text format.
+ *
+ * Iff <oids>, unload or reload the format that includes OID information.
+ * On input, we accept OIDs whether or not the table has an OID column,
+ * but silently drop them if it does not.  On output, we report an error
+ * if the user asks for OIDs in a table that has none (not providing an
+ * OID column might seem friendlier, but could seriously confuse programs).
+ *
+ * If in the text format, delimit columns with delimiter <delim> and print
+ * NULL values as <null_print>.
+ */
+static CopyState
+BeginCopy(bool is_from,
+		  Relation rel,
+		  Node *raw_query,
+		  const char *queryString,
+		  List *attnamelist,
+		  List *options)
+{
+	CopyState	cstate;
+	TupleDesc	tupDesc;
+	int			num_phys_attrs;
+	MemoryContext oldcontext;
+
+	/* Allocate workspace and zero all fields */
+	cstate = (CopyStateData *) palloc0(sizeof(CopyStateData));
+
+	/*
+	 * We allocate everything used by a cstate in a new memory context.
+	 * This avoids memory leaks during repeated use of COPY in a query.
+	 */
+	cstate->copycontext = AllocSetContextCreate(CurrentMemoryContext,
+												"COPY",
+												ALLOCSET_DEFAULT_MINSIZE,
+												ALLOCSET_DEFAULT_INITSIZE,
+												ALLOCSET_DEFAULT_MAXSIZE);
+
+	oldcontext = MemoryContextSwitchTo(cstate->copycontext);
+
+	/* Extract options from the statement node tree */
+	ProcessCopyOptions(cstate, is_from, options);
+
+	/* Process the source/target relation or query */
 	if (rel)
 	{
 		Assert(!raw_query);
@ -1197,19 +1229,19 @@ BeginCopy(bool is_from,

 	/* Convert FORCE QUOTE name list to per-column flags, check validity */
 	cstate->force_quote_flags = (bool *) palloc0(num_phys_attrs * sizeof(bool));
-	if (force_quote_all)
+	if (cstate->force_quote_all)
 	{
 		int			i;

 		for (i = 0; i < num_phys_attrs; i++)
 			cstate->force_quote_flags[i] = true;
 	}
-	else if (force_quote)
+	else if (cstate->force_quote)
 	{
 		List	   *attnums;
 		ListCell   *cur;

-		attnums = CopyGetAttnums(tupDesc, cstate->rel, force_quote);
+		attnums = CopyGetAttnums(tupDesc, cstate->rel, cstate->force_quote);

 		foreach(cur, attnums)
 		{
@ -1226,12 +1258,12 @@ BeginCopy(bool is_from,

 	/* Convert FORCE NOT NULL name list to per-column flags, check validity */
 	cstate->force_notnull_flags = (bool *) palloc0(num_phys_attrs * sizeof(bool));
-	if (force_notnull)
+	if (cstate->force_notnull)
 	{
 		List	   *attnums;
 		ListCell   *cur;

-		attnums = CopyGetAttnums(tupDesc, cstate->rel, force_notnull);
+		attnums = CopyGetAttnums(tupDesc, cstate->rel, cstate->force_notnull);

 		foreach(cur, attnums)
 		{
--- a/src/include/commands/copy.h
+++ b/src/include/commands/copy.h
@ -18,11 +18,12 @@
 #include "nodes/parsenodes.h"
 #include "tcop/dest.h"

-
-typedef struct CopyStateData  *CopyState;
+/* CopyStateData is private in commands/copy.c */
+typedef struct CopyStateData *CopyState;

 extern uint64 DoCopy(const CopyStmt *stmt, const char *queryString);

+extern void ProcessCopyOptions(CopyState cstate, bool is_from, List *options);
 extern CopyState BeginCopyFrom(Relation rel, const char *filename,
 							   List *attnamelist, List *options);
 extern void EndCopyFrom(CopyState cstate);