Add HEADER support to COPY text format

The COPY CSV format supports the HEADER option to output a header
line.  This patch adds the same option to the default text format.  On
input, the HEADER option causes the first line to be skipped, same as
with CSV.

Author: Rémi Lapeyre <remi.lapeyre@lenstra.fr>
Discussion: https://www.postgresql.org/message-id/flat/CAF1-J-0PtCWMeLtswwGV2M70U26n4g33gpe1rcKQqe6wVQDrFA@mail.gmail.com

src/backend/commands/copy.c

@@ -555,10 +555,10 @@ ProcessCopyOptions(ParseState *pstate,
 				 errmsg("COPY delimiter cannot be \"%s\"", opts_out->delim)));
 
 	/* Check header */
-	if (!opts_out->csv_mode && opts_out->header_line)
+	if (opts_out->binary && opts_out->header_line)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("COPY HEADER available only in CSV mode")));
+				 errmsg("cannot specify HEADER in BINARY mode")));
 
 	/* Check quote */
 	if (!opts_out->csv_mode && opts_out->quote != NULL)

src/backend/commands/copyto.c

@@ -863,8 +863,11 @@ DoCopyTo(CopyToState cstate)
 
 				colname = NameStr(TupleDescAttr(tupDesc, attnum - 1)->attname);
 
-				CopyAttributeOutCSV(cstate, colname, false,
+				if (cstate->opts.csv_mode)
+					CopyAttributeOutCSV(cstate, colname, false,
 									list_length(cstate->attnumlist) == 1);
+				else
+					CopyAttributeOutText(cstate, colname);
 			}
 
 			CopySendEndOfRow(cstate);

src/include/commands/copy.h

@@ -32,7 +32,7 @@ typedef struct CopyFormatOptions
 	bool		binary;			/* binary format? */
 	bool		freeze;			/* freeze rows on loading? */
 	bool		csv_mode;		/* Comma Separated Value format? */
-	bool		header_line;	/* CSV header line? */
+	bool		header_line;	/* header line? */
 	char	   *null_print;		/* NULL marker string (server encoding!) */
 	int			null_print_len; /* length of same */
 	char	   *null_print_client;	/* same converted to file encoding */

src/test/regress/expected/copy.out

@@ -120,6 +120,14 @@ copy copytest3 to stdout csv header;
 c1,"col with , comma","col with "" quote"
 1,a,1
 2,b,2
+create temp table copytest4 (
+	c1 int,
+	"colname with tab: 	" text);
+copy copytest4 from stdin (header);
+copy copytest4 to stdout (header);
+c1	colname with tab: \t
+1	a
+2	b
 -- test copy from with a partitioned table
 create table parted_copytest (
 	a int,

src/test/regress/sql/copy.sql

@@ -160,6 +160,18 @@ this is just a line full of junk that would error out if parsed
 
 copy copytest3 to stdout csv header;
 
+create temp table copytest4 (
+	c1 int,
+	"colname with tab: 	" text);
+
+copy copytest4 from stdin (header);
+this is just a line full of junk that would error out if parsed
+1	a
+2	b
+\.
+
+copy copytest4 to stdout (header);
+
 -- test copy from with a partitioned table
 create table parted_copytest (
 	a int,