Add ENCODING option to COPY

diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml
index 38424ad..1f9e4cc 100644
--- a/doc/src/sgml/ref/copy.sgml
+++ b/doc/src/sgml/ref/copy.sgml
@@ -40,7 +40,8 @@ COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable
     QUOTE '<replaceable class="parameter">quote_character</replaceable>'
     ESCAPE '<replaceable class="parameter">escape_character</replaceable>'
     FORCE_QUOTE { ( <replaceable class="parameter">column</replaceable> [, ...] ) | * }
-    FORCE_NOT_NULL ( <replaceable class="parameter">column</replaceable> [, ...] )
+    FORCE_NOT_NULL ( <replaceable class="parameter">column</replaceable> [, ...] ) |
+    ENCODING <replaceable class="parameter">encoding_name</replaceable>
 </synopsis>
  </refsynopsisdiv>
 
@@ -282,6 +283,18 @@ COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>ENCODING</></term>
+    <listitem>
+     <para>
+      Specifies that the file is encoded in the <replaceable
+      class="parameter">encoding_name</replaceable>.  If this option is
+      omitted, the current client encoding is used. See the Notes below
+      for more details.
+     </para>
+    </listitem>
+   </varlistentry>
+
   </variablelist>
  </refsect1>
 
@@ -377,8 +390,9 @@ COPY <replaceable class="parameter">count</replaceable>
    </para>
 
    <para>
-    Input data is interpreted according to the current client encoding,
-    and output data is encoded in the current client encoding, even
+    Input data is interpreted according to <literal>ENCODING</literal>
+    option or the current client encoding, and output data is encoded
+    in <literal>ENCODING</literal> or the current client encoding, even
     if the data does not pass through the client but is read from or
     written to a file directly by the server.
    </para>
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 841bf22..0c85842 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -97,7 +97,9 @@ typedef struct CopyStateData
 	bool		fe_eof;			/* true if detected end of copy data */
 	EolType		eol_type;		/* EOL type of input */
 	int			client_encoding;	/* remote side's character encoding */
-	bool		need_transcoding;		/* client encoding diff from server? */
+	int			saved_encoding;		/* client encoding to be restored */
+	bool		encoding_option;	/* has encoding option? */
+	bool		need_transcoding;		/* encoding diff from server? */
 	bool		encoding_embeds_ascii;	/* ASCII can be non-first byte? */
 	uint64		processed;		/* # of tuples processed */
 
@@ -811,6 +813,22 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 						 errmsg("conflicting or redundant options")));
 			cstate->escape = defGetString(defel);
 		}
+		else if (strcmp(defel->defname, "encoding") == 0)
+		{
+			if (cstate->encoding_option)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			if (PG_VALID_ENCODING(pg_char_to_encoding(defGetString(defel))))
+					cstate->client_encoding =
+							pg_char_to_encoding(defGetString(defel));
+			else
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("argument to option \"%s\" must be a valid encoding name",
+								defel->defname)));
+			cstate->encoding_option = true;
+		}
 		else if (strcmp(defel->defname, "force_quote") == 0)
 		{
 			if (force_quote || force_quote_all)
@@ -1169,11 +1187,25 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 	cstate->processed = 0;
 
 	/*
-	 * Set up encoding conversion info.  Even if the client and server
-	 * encodings are the same, we must apply pg_client_to_server() to validate
-	 * data in multibyte encodings.
+	 * Set up encoding conversion info.  If encoding option is specified,
+	 * use it instead of client_encoding of GUC.  In any cases, we use
+	 * pg_client_to_server/server_to_client() for performance reason.
+	 * Be careful to restore the previous encoding setting on changing
+	 * current client_encoding.
+	 */
+	if (cstate->encoding_option)
+	{
+		cstate->saved_encoding = pg_get_client_encoding();
+		SetClientEncoding(cstate->client_encoding, true);
+	}
+	else
+		cstate->client_encoding = pg_get_client_encoding();
+
+	/*
+	 * Even if the client and server encodings are the same,
+	 * we must apply pg_client_to_server() to validate data in
+	 * multibyte encodings.
 	 */
-	cstate->client_encoding = pg_get_client_encoding();
 	cstate->need_transcoding =
 		(cstate->client_encoding != GetDatabaseEncoding() ||
 		 pg_database_encoding_max_length() > 1);
@@ -1188,6 +1220,10 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 	else
 		DoCopyTo(cstate);		/* copy from database to file */
 
+	/* restore the previous client_encoding if it has changed */
+	if (cstate->encoding_option)
+		SetClientEncoding(cstate->saved_encoding, true);
+
 	/*
 	 * Close the relation or query.  If reading, we can release the
 	 * AccessShareLock we got; if writing, we should hold the lock until end
@@ -1571,6 +1607,14 @@ copy_in_error_callback(void *arg)
 {
 	CopyState	cstate = (CopyState) arg;
 
+	/*
+	 * If we changed encoding by the option, need to restore
+	 * the original client encoding so that error message
+	 * can be encoded in the proper one.
+	 */
+	if (cstate->encoding_option)
+		SetClientEncoding(cstate->saved_encoding, true);
+
 	if (cstate->binary)
 	{
 		/* can't usefully display the data */
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 456db5c..1f698d1 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -2217,6 +2217,10 @@ copy_opt_item:
 				{
 					$$ = makeDefElem("force_not_null", (Node *)$4);
 				}
+			| ENCODING ColId_or_Sconst
+				{
+					$$ = makeDefElem("encoding", (Node *)makeString($2));
+				}
 		;
 
 /* The following exist for backward compatibility with very old versions */
diff --git a/src/test/regress/expected/copy2.out b/src/test/regress/expected/copy2.out
index 15cbe02..88d7d16 100644
--- a/src/test/regress/expected/copy2.out
+++ b/src/test/regress/expected/copy2.out
@@ -46,10 +46,10 @@ CONTEXT:  COPY x, line 1: "2001	231	\N	\N"
 COPY x from stdin;
 ERROR:  extra data after last expected column
 CONTEXT:  COPY x, line 1: "2002	232	40	50	60	70	80"
--- various COPY options: delimiters, oids, NULL string
+-- various COPY options: delimiters, oids, NULL string, encoding
 COPY x (b, c, d, e) from stdin with oids delimiter ',' null 'x';
 COPY x from stdin WITH DELIMITER AS ';' NULL AS '';
-COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X';
+COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X' ENCODING sql_ascii;
 -- check results of copy in
 SELECT * FROM x;
    a   | b  |     c      |   d    |          e           
@@ -187,7 +187,7 @@ COPY y TO stdout WITH CSV QUOTE '''' DELIMITER '|';
 Jackson, Sam|\h
 It is "perfect".|	
 ''|
-COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\';
+COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\' ENCODING sql_ascii;
 "Jackson, Sam","\\h"
 "It is \"perfect\".","	"
 "",
diff --git a/src/test/regress/sql/copy2.sql b/src/test/regress/sql/copy2.sql
index c2e8b03..d2683d1 100644
--- a/src/test/regress/sql/copy2.sql
+++ b/src/test/regress/sql/copy2.sql
@@ -72,7 +72,7 @@ COPY x from stdin;
 2002	232	40	50	60	70	80
 \.
 
--- various COPY options: delimiters, oids, NULL string
+-- various COPY options: delimiters, oids, NULL string, encoding
 COPY x (b, c, d, e) from stdin with oids delimiter ',' null 'x';
 500000,x,45,80,90
 500001,x,\x,\\x,\\\x
@@ -83,7 +83,7 @@ COPY x from stdin WITH DELIMITER AS ';' NULL AS '';
 3000;;c;;
 \.
 
-COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X';
+COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X' ENCODING sql_ascii;
 4000:\X:C:\X:\X
 4001:1:empty::
 4002:2:null:\X:\X
@@ -127,7 +127,7 @@ INSERT INTO y VALUES ('', NULL);
 
 COPY y TO stdout WITH CSV;
 COPY y TO stdout WITH CSV QUOTE '''' DELIMITER '|';
-COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\';
+COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\' ENCODING sql_ascii;
 COPY y TO stdout WITH CSV FORCE QUOTE *;
 
 -- Repeat above tests with new 9.0 option syntax

diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 93fb2cf..6ea9372 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -1370,8 +1370,13 @@ CopyTo(CopyState cstate)
 	/* We use fe_msgbuf as a per-row buffer regardless of copy_dest */
 	cstate->fe_msgbuf = makeStringInfo();
 
-	/* Setup encoding conversion proc */
-	if (cstate->need_transcoding)
+	/*
+	 * We don't need conversion procedure when the encodings match
+	 * between target and server, but need_transcoding indicates
+	 * we need verify encoding still.
+	 */
+	if (cstate->need_transcoding &&
+		cstate->target_encoding != GetDatabaseEncoding())
 	{
 		Oid		funcoid;
 
@@ -1380,6 +1385,8 @@ CopyTo(CopyState cstate)
 		cstate->conv_proc = (FmgrInfo *) palloc(sizeof(FmgrInfo));
 		fmgr_info(funcoid, cstate->conv_proc);
 	}
+	else
+		cstate->conv_proc = NULL;
 
 	/* Get info about the columns we need to process. */
 	cstate->out_functions = (FmgrInfo *) palloc(num_phys_attrs * sizeof(FmgrInfo));
@@ -1989,8 +1996,13 @@ CopyFrom(CopyState cstate)
 	cstate->cur_attname = NULL;
 	cstate->cur_attval = NULL;
 
-	/* Setup encoding conversion proc */
-	if (cstate->need_transcoding)
+	/*
+	 * We don't need conversion procedure when the encodings match
+	 * between target and server, but need_transcoding indicates
+	 * we need verify encoding still.
+	 */
+	if (cstate->need_transcoding &&
+		cstate->target_encoding != GetDatabaseEncoding())
 	{
 		Oid		funcoid;
 
@@ -1999,6 +2011,8 @@ CopyFrom(CopyState cstate)
 		cstate->conv_proc = (FmgrInfo *) palloc(sizeof(FmgrInfo));
 		fmgr_info(funcoid, cstate->conv_proc);
 	}
+	else
+		cstate->conv_proc = NULL;
 
 	bistate = GetBulkInsertState();
 

diff --git a/doc/src/sgml/ref/copy.sgml b/doc/src/sgml/ref/copy.sgml
index 38424ad..1f9e4cc 100644
--- a/doc/src/sgml/ref/copy.sgml
+++ b/doc/src/sgml/ref/copy.sgml
@@ -40,7 +40,8 @@ COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable
     QUOTE '<replaceable class="parameter">quote_character</replaceable>'
     ESCAPE '<replaceable class="parameter">escape_character</replaceable>'
     FORCE_QUOTE { ( <replaceable class="parameter">column</replaceable> [, ...] ) | * }
-    FORCE_NOT_NULL ( <replaceable class="parameter">column</replaceable> [, ...] )
+    FORCE_NOT_NULL ( <replaceable class="parameter">column</replaceable> [, ...] ) |
+    ENCODING <replaceable class="parameter">encoding_name</replaceable>
 </synopsis>
  </refsynopsisdiv>
 
@@ -282,6 +283,18 @@ COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>ENCODING</></term>
+    <listitem>
+     <para>
+      Specifies that the file is encoded in the <replaceable
+      class="parameter">encoding_name</replaceable>.  If this option is
+      omitted, the current client encoding is used. See the Notes below
+      for more details.
+     </para>
+    </listitem>
+   </varlistentry>
+
   </variablelist>
  </refsect1>
 
@@ -377,8 +390,9 @@ COPY <replaceable class="parameter">count</replaceable>
    </para>
 
    <para>
-    Input data is interpreted according to the current client encoding,
-    and output data is encoded in the current client encoding, even
+    Input data is interpreted according to <literal>ENCODING</literal>
+    option or the current client encoding, and output data is encoded
+    in <literal>ENCODING</literal> or the current client encoding, even
     if the data does not pass through the client but is read from or
     written to a file directly by the server.
    </para>
diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 841bf22..6ea9372 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -96,9 +96,11 @@ typedef struct CopyStateData
 	bool		fe_copy;		/* true for all FE copy dests */
 	bool		fe_eof;			/* true if detected end of copy data */
 	EolType		eol_type;		/* EOL type of input */
-	int			client_encoding;	/* remote side's character encoding */
-	bool		need_transcoding;		/* client encoding diff from server? */
+	int			target_encoding;	/* remote side's character encoding */
+	bool		encoding_option;	/* has encoding option? */
+	bool		need_transcoding;		/* encoding diff from server? */
 	bool		encoding_embeds_ascii;	/* ASCII can be non-first byte? */
+	FmgrInfo   *conv_proc;		/* encoding conversion proc */
 	uint64		processed;		/* # of tuples processed */
 
 	/* parameters from the COPY command */
@@ -811,6 +813,22 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 						 errmsg("conflicting or redundant options")));
 			cstate->escape = defGetString(defel);
 		}
+		else if (strcmp(defel->defname, "encoding") == 0)
+		{
+			if (cstate->encoding_option)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			if (PG_VALID_ENCODING(pg_char_to_encoding(defGetString(defel))))
+					cstate->target_encoding =
+							pg_char_to_encoding(defGetString(defel));
+			else
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("argument to option \"%s\" must be a valid encoding name",
+								defel->defname)));
+			cstate->encoding_option = true;
+		}
 		else if (strcmp(defel->defname, "force_quote") == 0)
 		{
 			if (force_quote || force_quote_all)
@@ -1169,16 +1187,22 @@ DoCopy(const CopyStmt *stmt, const char *queryString)
 	cstate->processed = 0;
 
 	/*
-	 * Set up encoding conversion info.  Even if the client and server
-	 * encodings are the same, we must apply pg_client_to_server() to validate
-	 * data in multibyte encodings.
+	 * Set up encoding conversion info.  If encoding option is specified,
+	 * use it instead of client_encoding of GUC.
+	 */
+	if (!cstate->encoding_option)
+		cstate->target_encoding = pg_get_client_encoding();
+
+	/*
+	 * Even if the client and server encodings are the same,
+	 * we must apply pg_client_to_server() to validate data in
+	 * multibyte encodings.
 	 */
-	cstate->client_encoding = pg_get_client_encoding();
 	cstate->need_transcoding =
-		(cstate->client_encoding != GetDatabaseEncoding() ||
+		(cstate->target_encoding != GetDatabaseEncoding() ||
 		 pg_database_encoding_max_length() > 1);
 	/* See Multibyte encoding comment above */
-	cstate->encoding_embeds_ascii = PG_ENCODING_IS_CLIENT_ONLY(cstate->client_encoding);
+	cstate->encoding_embeds_ascii = PG_ENCODING_IS_CLIENT_ONLY(cstate->target_encoding);
 
 	cstate->copy_dest = COPY_FILE;		/* default */
 	cstate->filename = stmt->filename;
@@ -1346,6 +1370,24 @@ CopyTo(CopyState cstate)
 	/* We use fe_msgbuf as a per-row buffer regardless of copy_dest */
 	cstate->fe_msgbuf = makeStringInfo();
 
+	/*
+	 * We don't need conversion procedure when the encodings match
+	 * between target and server, but need_transcoding indicates
+	 * we need verify encoding still.
+	 */
+	if (cstate->need_transcoding &&
+		cstate->target_encoding != GetDatabaseEncoding())
+	{
+		Oid		funcoid;
+
+		funcoid = FindDefaultConversionProc(
+									GetDatabaseEncoding(), cstate->target_encoding);
+		cstate->conv_proc = (FmgrInfo *) palloc(sizeof(FmgrInfo));
+		fmgr_info(funcoid, cstate->conv_proc);
+	}
+	else
+		cstate->conv_proc = NULL;
+
 	/* Get info about the columns we need to process. */
 	cstate->out_functions = (FmgrInfo *) palloc(num_phys_attrs * sizeof(FmgrInfo));
 	foreach(cur, cstate->attnumlist)
@@ -1400,8 +1442,13 @@ CopyTo(CopyState cstate)
 		 * encoding, because it will be sent directly with CopySendString.
 		 */
 		if (cstate->need_transcoding)
-			cstate->null_print_client = pg_server_to_client(cstate->null_print,
-													 cstate->null_print_len);
+			cstate->null_print_client =
+				pg_cached_encoding_conversion(cstate->null_print,
+											  cstate->null_print_len,
+											  cstate->conv_proc,
+											  GetDatabaseEncoding(),
+											  cstate->target_encoding,
+											  false);
 
 		/* if a header has been requested send the line */
 		if (cstate->header_line)
@@ -1949,6 +1996,24 @@ CopyFrom(CopyState cstate)
 	cstate->cur_attname = NULL;
 	cstate->cur_attval = NULL;
 
+	/*
+	 * We don't need conversion procedure when the encodings match
+	 * between target and server, but need_transcoding indicates
+	 * we need verify encoding still.
+	 */
+	if (cstate->need_transcoding &&
+		cstate->target_encoding != GetDatabaseEncoding())
+	{
+		Oid		funcoid;
+
+		funcoid = FindDefaultConversionProc(
+								cstate->target_encoding, GetDatabaseEncoding());
+		cstate->conv_proc = (FmgrInfo *) palloc(sizeof(FmgrInfo));
+		fmgr_info(funcoid, cstate->conv_proc);
+	}
+	else
+		cstate->conv_proc = NULL;
+
 	bistate = GetBulkInsertState();
 
 	/* Set up callback to identify error line number */
@@ -2351,8 +2416,12 @@ CopyReadLine(CopyState cstate)
 	{
 		char	   *cvt;
 
-		cvt = pg_client_to_server(cstate->line_buf.data,
-								  cstate->line_buf.len);
+		cvt = pg_cached_encoding_conversion(cstate->line_buf.data,
+											cstate->line_buf.len,
+											cstate->conv_proc,
+											cstate->target_encoding,
+											GetDatabaseEncoding(),
+											true);
 		if (cvt != cstate->line_buf.data)
 		{
 			/* transfer converted data back to line_buf */
@@ -2711,7 +2780,7 @@ not_end_of_copy:
 
 			mblen_str[0] = c;
 			/* All our encodings only read the first byte to get the length */
-			mblen = pg_encoding_mblen(cstate->client_encoding, mblen_str);
+			mblen = pg_encoding_mblen(cstate->target_encoding, mblen_str);
 			IF_NEED_REFILL_AND_NOT_EOF_CONTINUE(mblen - 1);
 			IF_NEED_REFILL_AND_EOF_BREAK(mblen - 1);
 			raw_buf_ptr += mblen - 1;
@@ -3210,7 +3279,11 @@ CopyAttributeOutText(CopyState cstate, char *string)
 	char		delimc = cstate->delim[0];
 
 	if (cstate->need_transcoding)
-		ptr = pg_server_to_client(string, strlen(string));
+		ptr = pg_cached_encoding_conversion(string, strlen(string),
+											cstate->conv_proc,
+											GetDatabaseEncoding(),
+											cstate->target_encoding,
+											false);
 	else
 		ptr = string;
 
@@ -3283,7 +3356,7 @@ CopyAttributeOutText(CopyState cstate, char *string)
 				start = ptr++;	/* we include char in next run */
 			}
 			else if (IS_HIGHBIT_SET(c))
-				ptr += pg_encoding_mblen(cstate->client_encoding, ptr);
+				ptr += pg_encoding_mblen(cstate->target_encoding, ptr);
 			else
 				ptr++;
 		}
@@ -3370,7 +3443,11 @@ CopyAttributeOutCSV(CopyState cstate, char *string,
 		use_quote = true;
 
 	if (cstate->need_transcoding)
-		ptr = pg_server_to_client(string, strlen(string));
+		ptr = pg_cached_encoding_conversion(string, strlen(string),
+											cstate->conv_proc,
+											GetDatabaseEncoding(),
+											cstate->target_encoding,
+											false);
 	else
 		ptr = string;
 
@@ -3397,7 +3474,7 @@ CopyAttributeOutCSV(CopyState cstate, char *string,
 					break;
 				}
 				if (IS_HIGHBIT_SET(c) && cstate->encoding_embeds_ascii)
-					tptr += pg_encoding_mblen(cstate->client_encoding, tptr);
+					tptr += pg_encoding_mblen(cstate->target_encoding, tptr);
 				else
 					tptr++;
 			}
@@ -3421,7 +3498,7 @@ CopyAttributeOutCSV(CopyState cstate, char *string,
 				start = ptr;	/* we include char in next run */
 			}
 			if (IS_HIGHBIT_SET(c) && cstate->encoding_embeds_ascii)
-				ptr += pg_encoding_mblen(cstate->client_encoding, ptr);
+				ptr += pg_encoding_mblen(cstate->target_encoding, ptr);
 			else
 				ptr++;
 		}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 456db5c..1f698d1 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -2217,6 +2217,10 @@ copy_opt_item:
 				{
 					$$ = makeDefElem("force_not_null", (Node *)$4);
 				}
+			| ENCODING ColId_or_Sconst
+				{
+					$$ = makeDefElem("encoding", (Node *)makeString($2));
+				}
 		;
 
 /* The following exist for backward compatibility with very old versions */
diff --git a/src/backend/utils/mb/mbutils.c b/src/backend/utils/mb/mbutils.c
index a041812..b38b7a0 100644
--- a/src/backend/utils/mb/mbutils.c
+++ b/src/backend/utils/mb/mbutils.c
@@ -71,8 +71,11 @@ static int	pending_client_encoding = PG_SQL_ASCII;
 
 
 /* Internal functions */
-static char *perform_default_encoding_conversion(const char *src,
-									int len, bool is_client_to_server);
+static bool need_conversion(const char *src, int len,
+							int src_encoding, int dest_encoding, bool check_sanity);
+static char *perform_cached_encoding_conversion(const char *src,
+												int len, FmgrInfo *flinfo,
+												int src_encoding, int dest_encoding);
 static int	cliplen(const char *str, int len, int limit);
 
 
@@ -500,50 +503,12 @@ pg_client_to_server(const char *s, int len)
 	Assert(DatabaseEncoding);
 	Assert(ClientEncoding);
 
-	if (len <= 0)
+	if (!need_conversion(s, len, ClientEncoding->encoding,
+						 DatabaseEncoding->encoding, true))
 		return (char *) s;
 
-	if (ClientEncoding->encoding == DatabaseEncoding->encoding ||
-		ClientEncoding->encoding == PG_SQL_ASCII)
-	{
-		/*
-		 * No conversion is needed, but we must still validate the data.
-		 */
-		(void) pg_verify_mbstr(DatabaseEncoding->encoding, s, len, false);
-		return (char *) s;
-	}
-
-	if (DatabaseEncoding->encoding == PG_SQL_ASCII)
-	{
-		/*
-		 * No conversion is possible, but we must still validate the data,
-		 * because the client-side code might have done string escaping using
-		 * the selected client_encoding.  If the client encoding is ASCII-safe
-		 * then we just do a straight validation under that encoding.  For an
-		 * ASCII-unsafe encoding we have a problem: we dare not pass such data
-		 * to the parser but we have no way to convert it.	We compromise by
-		 * rejecting the data if it contains any non-ASCII characters.
-		 */
-		if (PG_VALID_BE_ENCODING(ClientEncoding->encoding))
-			(void) pg_verify_mbstr(ClientEncoding->encoding, s, len, false);
-		else
-		{
-			int			i;
-
-			for (i = 0; i < len; i++)
-			{
-				if (s[i] == '\0' || IS_HIGHBIT_SET(s[i]))
-					ereport(ERROR,
-							(errcode(ERRCODE_CHARACTER_NOT_IN_REPERTOIRE),
-					 errmsg("invalid byte value for encoding \"%s\": 0x%02x",
-							pg_enc2name_tbl[PG_SQL_ASCII].name,
-							(unsigned char) s[i])));
-			}
-		}
-		return (char *) s;
-	}
-
-	return perform_default_encoding_conversion(s, len, true);
+	return perform_cached_encoding_conversion(s, len, ToServerConvProc,
+				ClientEncoding->encoding, DatabaseEncoding->encoding);
 }
 
 /*
@@ -555,43 +520,101 @@ pg_server_to_client(const char *s, int len)
 	Assert(DatabaseEncoding);
 	Assert(ClientEncoding);
 
+	if (!need_conversion(s, len, DatabaseEncoding->encoding,
+						 ClientEncoding->encoding, false))
+		return (char *) s;
+	return perform_cached_encoding_conversion(s, len, ToClientConvProc,
+				DatabaseEncoding->encoding, ClientEncoding->encoding);
+}
+
+/*
+ * given conversion Fmgr, do encoding conversion with sanity check if needed.
+ */
+char *
+pg_cached_encoding_conversion(const char *s, int len, FmgrInfo *convproc,
+					int src_encoding, int dest_encoding, bool check_sanity)
+{
 	if (len <= 0)
 		return (char *) s;
 
-	if (ClientEncoding->encoding == DatabaseEncoding->encoding ||
-		ClientEncoding->encoding == PG_SQL_ASCII ||
-		DatabaseEncoding->encoding == PG_SQL_ASCII)
-		return (char *) s;		/* assume data is valid */
+	if (!need_conversion(s, len, src_encoding, dest_encoding, check_sanity))
+		return (char *) s;
 
-	return perform_default_encoding_conversion(s, len, false);
+	return perform_cached_encoding_conversion(s, len, convproc,
+											  src_encoding, dest_encoding);
 }
 
 /*
+ * returns true if conversion is needed. check_sanity = true means
+ * the source string should be verified even though the conversion happened.
+ */
+static bool
+need_conversion(const char *s, int len, int src_encoding, int dest_encoding,
+				bool check_sanity)
+{
+	if (check_sanity)
+	{
+		if (src_encoding == dest_encoding || src_encoding == PG_SQL_ASCII)
+		{
+			/*
+			 * No conversion is needed, but we must still validate the data.
+			 */
+			(void) pg_verify_mbstr(src_encoding, s, len, false);
+			return false;
+		}
+
+		if (dest_encoding == PG_SQL_ASCII)
+		{
+			/*
+			 * No conversion is possible, but we must still validate the
+			 * data, because the client-side code might have done string
+			 * escaping using the selected client_encoding.  If the client
+			 * encoding is ASCII-safe then we just do a straight validation
+			 * under that encoding.  For an ASCII-unsafe encoding we have a
+			 * problem: we dare not pass such data to the parser but we have
+			 * no way to convert it.	We compromise by rejecting the data
+			 * if it contains any non-ASCII characters.
+			 */
+			if (PG_VALID_BE_ENCODING(src_encoding))
+				(void) pg_verify_mbstr(src_encoding, s, len, false);
+			else
+			{
+				int		i;
+
+				for (i = 0; i < len; i++)
+				{
+					if (s[i] == '\0' || IS_HIGHBIT_SET(s[i]))
+						ereport(ERROR,
+								(errcode(ERRCODE_CHARACTER_NOT_IN_REPERTOIRE),
+						 errmsg("invalid byte value for encoding \"%s\": 0x%02x",
+								pg_enc2name_tbl[PG_SQL_ASCII].name,
+								(unsigned char) s[i])));
+				}
+			}
+			return false;
+		}
+	}
+	else
+	{
+		if (src_encoding == dest_encoding ||
+			src_encoding == PG_SQL_ASCII ||
+			dest_encoding == PG_SQL_ASCII)
+			return false;
+	}
+
+	return true;
+}
+/*
  *	Perform default encoding conversion using cached FmgrInfo. Since
  *	this function does not access database at all, it is safe to call
  *	outside transactions.  If the conversion has not been set up by
  *	SetClientEncoding(), no conversion is performed.
  */
 static char *
-perform_default_encoding_conversion(const char *src, int len, bool is_client_to_server)
+perform_cached_encoding_conversion(const char *src, int len,
+					FmgrInfo *flinfo, int src_encoding, int dest_encoding)
 {
 	char	   *result;
-	int			src_encoding,
-				dest_encoding;
-	FmgrInfo   *flinfo;
-
-	if (is_client_to_server)
-	{
-		src_encoding = ClientEncoding->encoding;
-		dest_encoding = DatabaseEncoding->encoding;
-		flinfo = ToServerConvProc;
-	}
-	else
-	{
-		src_encoding = DatabaseEncoding->encoding;
-		dest_encoding = ClientEncoding->encoding;
-		flinfo = ToClientConvProc;
-	}
 
 	if (flinfo == NULL)
 		return (char *) src;
diff --git a/src/include/mb/pg_wchar.h b/src/include/mb/pg_wchar.h
index f110723..576773e 100644
--- a/src/include/mb/pg_wchar.h
+++ b/src/include/mb/pg_wchar.h
@@ -21,6 +21,10 @@
 
 #include <sys/types.h>
 
+#ifndef FRONTEND
+#include <fmgr.h>
+#endif
+
 /*
  * The pg_wchar type
  */
@@ -421,6 +425,12 @@ extern unsigned char *pg_do_encoding_conversion(unsigned char *src, int len,
 extern char *pg_client_to_server(const char *s, int len);
 extern char *pg_server_to_client(const char *s, int len);
 
+#ifndef FRONTEND
+extern char *pg_cached_encoding_conversion(const char *s, int len,
+						FmgrInfo *convproc, int src_encoding,
+						int dest_encoding, bool check_sanity);
+#endif
+
 extern unsigned short BIG5toCNS(unsigned short big5, unsigned char *lc);
 extern unsigned short CNStoBIG5(unsigned short cns, unsigned char lc);
 
diff --git a/src/test/regress/expected/copy2.out b/src/test/regress/expected/copy2.out
index 15cbe02..88d7d16 100644
--- a/src/test/regress/expected/copy2.out
+++ b/src/test/regress/expected/copy2.out
@@ -46,10 +46,10 @@ CONTEXT:  COPY x, line 1: "2001	231	\N	\N"
 COPY x from stdin;
 ERROR:  extra data after last expected column
 CONTEXT:  COPY x, line 1: "2002	232	40	50	60	70	80"
--- various COPY options: delimiters, oids, NULL string
+-- various COPY options: delimiters, oids, NULL string, encoding
 COPY x (b, c, d, e) from stdin with oids delimiter ',' null 'x';
 COPY x from stdin WITH DELIMITER AS ';' NULL AS '';
-COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X';
+COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X' ENCODING sql_ascii;
 -- check results of copy in
 SELECT * FROM x;
    a   | b  |     c      |   d    |          e           
@@ -187,7 +187,7 @@ COPY y TO stdout WITH CSV QUOTE '''' DELIMITER '|';
 Jackson, Sam|\h
 It is "perfect".|	
 ''|
-COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\';
+COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\' ENCODING sql_ascii;
 "Jackson, Sam","\\h"
 "It is \"perfect\".","	"
 "",
diff --git a/src/test/regress/sql/copy2.sql b/src/test/regress/sql/copy2.sql
index c2e8b03..d2683d1 100644
--- a/src/test/regress/sql/copy2.sql
+++ b/src/test/regress/sql/copy2.sql
@@ -72,7 +72,7 @@ COPY x from stdin;
 2002	232	40	50	60	70	80
 \.
 
--- various COPY options: delimiters, oids, NULL string
+-- various COPY options: delimiters, oids, NULL string, encoding
 COPY x (b, c, d, e) from stdin with oids delimiter ',' null 'x';
 500000,x,45,80,90
 500001,x,\x,\\x,\\\x
@@ -83,7 +83,7 @@ COPY x from stdin WITH DELIMITER AS ';' NULL AS '';
 3000;;c;;
 \.
 
-COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X';
+COPY x from stdin WITH DELIMITER AS ':' NULL AS E'\\X' ENCODING sql_ascii;
 4000:\X:C:\X:\X
 4001:1:empty::
 4002:2:null:\X:\X
@@ -127,7 +127,7 @@ INSERT INTO y VALUES ('', NULL);
 
 COPY y TO stdout WITH CSV;
 COPY y TO stdout WITH CSV QUOTE '''' DELIMITER '|';
-COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\';
+COPY y TO stdout WITH CSV FORCE QUOTE col2 ESCAPE E'\\' ENCODING sql_ascii;
 COPY y TO stdout WITH CSV FORCE QUOTE *;
 
 -- Repeat above tests with new 9.0 option syntax