v1-0001-Support-backslash-dot-on-a-line-by-itself-as-vali.patch

From 868b1e065cf714f315bab65129fd05a1d60fc81b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20V=C3=A9rit=C3=A9?= <daniel@manitou-mail.org>
Date: Mon, 18 Dec 2023 20:47:02 +0100
Subject: [PATCH v1] Support backslash-dot on a line by itself as valid data in
 COPY FROM...CSV

---
 doc/src/sgml/ref/psql-ref.sgml       |  4 ----
 src/backend/commands/copyfromparse.c | 13 ++---------
 src/bin/psql/copy.c                  | 32 ++++++++++++++++++++--------
 src/test/regress/expected/copy.out   | 15 +++++++++++++
 src/test/regress/sql/copy.sql        | 11 ++++++++++
 5 files changed, 51 insertions(+), 24 deletions(-)

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index cc7d797159..d94e3cacfc 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -1119,10 +1119,6 @@ INSERT INTO tbl1 VALUES ($1, $2) \bind 'first value' 'second value' \g
         destination, because all data must pass through the client/server
         connection.  For large amounts of data the <acronym>SQL</acronym>
         command might be preferable.
-        Also, because of this pass-through method, <literal>\copy
-        ... from</literal> in <acronym>CSV</acronym> mode will erroneously
-        treat a <literal>\.</literal> data value alone on a line as an
-        end-of-input marker.
         </para>
         </tip>
 
diff --git a/src/backend/commands/copyfromparse.c b/src/backend/commands/copyfromparse.c
index f553734582..b4c291b25b 100644
--- a/src/backend/commands/copyfromparse.c
+++ b/src/backend/commands/copyfromparse.c
@@ -1137,7 +1137,6 @@ CopyReadLineText(CopyFromState cstate)
 	bool		result = false;
 
 	/* CSV variables */
-	bool		first_char_in_line = true;
 	bool		in_quote = false,
 				last_was_esc = false;
 	char		quotec = '\0';
@@ -1335,10 +1334,9 @@ CopyReadLineText(CopyFromState cstate)
 		}
 
 		/*
-		 * In CSV mode, we only recognize \. alone on a line.  This is because
-		 * \. is a valid CSV data value.
+		 * In CSV mode, \. is a valid CSV data value anywhere in the line.
 		 */
-		if (c == '\\' && (!cstate->opts.csv_mode || first_char_in_line))
+		if (c == '\\' && !cstate->opts.csv_mode)
 		{
 			char		c2;
 
@@ -1442,14 +1440,7 @@ CopyReadLineText(CopyFromState cstate)
 			}
 		}
 
-		/*
-		 * This label is for CSV cases where \. appears at the start of a
-		 * line, but there is more text after it, meaning it was a data value.
-		 * We are more strict for \. in CSV mode because \. could be a data
-		 * value, while in non-CSV mode, \. cannot be a data value.
-		 */
 not_end_of_copy:
-		first_char_in_line = false;
 	}							/* end of outer loop */
 
 	/*
diff --git a/src/bin/psql/copy.c b/src/bin/psql/copy.c
index dbbbdb8898..f31a7acbb6 100644
--- a/src/bin/psql/copy.c
+++ b/src/bin/psql/copy.c
@@ -620,20 +620,34 @@ handleCopyIn(PGconn *conn, FILE *copystream, bool isbinary, PGresult **res)
 				/* current line is done? */
 				if (buf[buflen - 1] == '\n')
 				{
-					/* check for EOF marker, but not on a partial line */
-					if (at_line_begin)
+					/*
+					 * When at the beginning of the line, check for EOF marker.
+					 * If the marker is found and the data is inlined,
+					 * we must stop at this point.  If not, the \. line can be
+					 * sent to the server, and we let it decide whether
+					 * it's an EOF or not depending on the format: in
+					 * basic TEXT, \. is going to be interpreted as an EOF, in
+					 * CSV, it will not.
+					 */
+					if (at_line_begin && copystream == pset.cur_cmd_source)
 					{
-						/*
-						 * This code erroneously assumes '\.' on a line alone
-						 * inside a quoted CSV string terminates the \copy.
-						 * https://www.postgresql.org/message-id/E1TdNVQ-0001ju-GO@wrigleys.postgresql.org
-						 *
-						 * https://www.postgresql.org/message-id/bfcd57e4-8f23-4c3e-a5db-2571d09208e2@beta.fastmail.com
-						 */
 						if ((linelen == 3 && memcmp(fgresult, "\\.\n", 3) == 0) ||
 							(linelen == 4 && memcmp(fgresult, "\\.\r\n", 4) == 0))
 						{
 							copydone = true;
+							/*
+							 * Remove the EOF marker from the data sent, unless
+							 * using the obsolete v2 protocol that needs it.
+							 * In the case of CSV, the EOF marker must be
+							 * removed, otherwise it would be interpreted by
+							 * the server as valid data.
+							 */
+							if (copystream == pset.cur_cmd_source &&
+								PQprotocolVersion(conn) >= 3)
+							{
+								*fgresult='\0';
+								buflen -= linelen;
+							}
 						}
 					}
 
diff --git a/src/test/regress/expected/copy.out b/src/test/regress/expected/copy.out
index b48365ec98..fc1e6cfd7b 100644
--- a/src/test/regress/expected/copy.out
+++ b/src/test/regress/expected/copy.out
@@ -32,6 +32,21 @@ select * from copytest except select * from copytest2;
 -------+------+--------
 (0 rows)
 
+--- test unquoted .\ as data inside CSV
+truncate copytest2;
+insert into copytest2(test) values('line1'), ('\.'), ('line2');
+copy (select test from copytest2 order by test collate "C") to :'filename' csv;
+-- get the data back in with copy
+truncate copytest2;
+copy copytest2(test) from :'filename' csv;
+select test from copytest2 order by test collate "C";
+ test  
+-------
+ \.
+ line1
+ line2
+(3 rows)
+
 -- test header line feature
 create temp table copytest3 (
 	c1 int,
diff --git a/src/test/regress/sql/copy.sql b/src/test/regress/sql/copy.sql
index 43d2e906dd..24ecb0485a 100644
--- a/src/test/regress/sql/copy.sql
+++ b/src/test/regress/sql/copy.sql
@@ -38,6 +38,17 @@ copy copytest2 from :'filename' csv quote '''' escape E'\\';
 
 select * from copytest except select * from copytest2;
 
+--- test unquoted .\ as data inside CSV
+
+truncate copytest2;
+
+insert into copytest2(test) values('line1'), ('\.'), ('line2');
+copy (select test from copytest2 order by test collate "C") to :'filename' csv;
+-- get the data back in with copy
+truncate copytest2;
+copy copytest2(test) from :'filename' csv;
+select test from copytest2 order by test collate "C";
+
 
 -- test header line feature
 
-- 
2.34.1