copy: update docs for FORCE_NULL and FORCE_NOT_NULL combination

Also update regression tests

Patch by Michael Paquier

contrib/file_fdw/file_fdw.c

@@ -264,11 +264,6 @@ file_fdw_validator(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_SYNTAX_ERROR),
 						 errmsg("conflicting or redundant options"),
 						 errhint("option \"force_not_null\" supplied more than once for a column")));
-			if(force_null)
-				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("conflicting or redundant options"),
-						 errhint("option \"force_not_null\" cannot be used together with \"force_null\"")));
 			force_not_null = def;
 			/* Don't care what the value is, as long as it's a legal boolean */
 			(void) defGetBoolean(def);
@@ -281,11 +276,6 @@ file_fdw_validator(PG_FUNCTION_ARGS)
 						(errcode(ERRCODE_SYNTAX_ERROR),
 						 errmsg("conflicting or redundant options"),
 						 errhint("option \"force_null\" supplied more than once for a column")));
-			if(force_not_null)
-				ereport(ERROR,
-						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("conflicting or redundant options"),
-						 errhint("option \"force_null\" cannot be used together with \"force_not_null\"")));
 			force_null = def;
 			(void) defGetBoolean(def);
 		}

contrib/file_fdw/input/file_fdw.source

@@ -91,24 +91,22 @@ ALTER FOREIGN TABLE text_csv OPTIONS (SET format 'csv');
 \pset null _null_
 SELECT * FROM text_csv;
 
+-- force_not_null and force_null can be used together on the same column
+ALTER FOREIGN TABLE text_csv ALTER COLUMN word1 OPTIONS (force_null 'true');
+ALTER FOREIGN TABLE text_csv ALTER COLUMN word3 OPTIONS (force_not_null 'true');
+
 -- force_not_null is not allowed to be specified at any foreign object level:
 ALTER FOREIGN DATA WRAPPER file_fdw OPTIONS (ADD force_not_null '*'); -- ERROR
 ALTER SERVER file_server OPTIONS (ADD force_not_null '*'); -- ERROR
 CREATE USER MAPPING FOR public SERVER file_server OPTIONS (force_not_null '*'); -- ERROR
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (force_not_null '*'); -- ERROR
 
--- force_not_null cannot be specified together with force_null
-ALTER FOREIGN TABLE text_csv ALTER COLUMN word1 OPTIONS (force_null 'true'); --ERROR
-
 -- force_null is not allowed to be specified at any foreign object level:
 ALTER FOREIGN DATA WRAPPER file_fdw OPTIONS (ADD force_null '*'); -- ERROR
 ALTER SERVER file_server OPTIONS (ADD force_null '*'); -- ERROR
 CREATE USER MAPPING FOR public SERVER file_server OPTIONS (force_null '*'); -- ERROR
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (force_null '*'); -- ERROR
 
--- force_null cannot be specified together with force_not_null
-ALTER FOREIGN TABLE text_csv ALTER COLUMN word3 OPTIONS (force_not_null 'true'); --ERROR
-
 -- basic query tests
 SELECT * FROM agg_text WHERE b > 10.0 ORDER BY a;
 SELECT * FROM agg_csv ORDER BY a;

contrib/file_fdw/output/file_fdw.source

@@ -115,6 +115,9 @@ SELECT * FROM text_csv;
  ABC   | abc    |        | 
 (5 rows)
 
+-- force_not_null and force_null can be used together on the same column
+ALTER FOREIGN TABLE text_csv ALTER COLUMN word1 OPTIONS (force_null 'true');
+ALTER FOREIGN TABLE text_csv ALTER COLUMN word3 OPTIONS (force_not_null 'true');
 -- force_not_null is not allowed to be specified at any foreign object level:
 ALTER FOREIGN DATA WRAPPER file_fdw OPTIONS (ADD force_not_null '*'); -- ERROR
 ERROR:  invalid option "force_not_null"
@@ -128,10 +131,6 @@ HINT:  There are no valid options in this context.
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (force_not_null '*'); -- ERROR
 ERROR:  invalid option "force_not_null"
 HINT:  Valid options in this context are: filename, format, header, delimiter, quote, escape, null, encoding
--- force_not_null cannot be specified together with force_null
-ALTER FOREIGN TABLE text_csv ALTER COLUMN word1 OPTIONS (force_null 'true'); --ERROR
-ERROR:  conflicting or redundant options
-HINT:  option "force_null" cannot be used together with "force_not_null"
 -- force_null is not allowed to be specified at any foreign object level:
 ALTER FOREIGN DATA WRAPPER file_fdw OPTIONS (ADD force_null '*'); -- ERROR
 ERROR:  invalid option "force_null"
@@ -145,10 +144,6 @@ HINT:  There are no valid options in this context.
 CREATE FOREIGN TABLE tbl () SERVER file_server OPTIONS (force_null '*'); -- ERROR
 ERROR:  invalid option "force_null"
 HINT:  Valid options in this context are: filename, format, header, delimiter, quote, escape, null, encoding
--- force_null cannot be specified together with force_not_null
-ALTER FOREIGN TABLE text_csv ALTER COLUMN word3 OPTIONS (force_not_null 'true'); --ERROR
-ERROR:  conflicting or redundant options
-HINT:  option "force_not_null" cannot be used together with "force_null"
 -- basic query tests
 SELECT * FROM agg_text WHERE b > 10.0 ORDER BY a;
   a  |   b    

doc/src/sgml/ref/copy.sgml

@@ -487,6 +487,13 @@ COPY <replaceable class="parameter">count</replaceable>
     <command>VACUUM</command> to recover the wasted space.
    </para>
 
+   <para>
+    <literal>FORCE_NULL</> and <literal>FORCE_NOT_NULL</> can be used
+    simultaneously on the same column. This has as result to convert quoted
+    null strings to null values and to convert unquoted null strings to
+    empty strings.
+   </para>
+
  </refsect1>
 
  <refsect1>

src/test/regress/expected/copy2.out

@@ -383,7 +383,6 @@ SELECT * FROM vistest;
 (2 rows)
 
 -- Test FORCE_NOT_NULL and FORCE_NULL options
--- should succeed with "b" set to an empty string and "c" set to NULL
 CREATE TEMP TABLE forcetest (
     a INT NOT NULL,
     b TEXT NOT NULL,
@@ -392,6 +391,7 @@ CREATE TEMP TABLE forcetest (
     e TEXT
 );
 \pset null NULL
+-- should succeed with no effect ("b" remains an empty string, "c" remains NULL)
 BEGIN;
 COPY forcetest (a, b, c) FROM STDIN WITH (FORMAT csv, FORCE_NOT_NULL(b), FORCE_NULL(c));
 COMMIT;
@@ -401,12 +401,12 @@ SELECT b, c FROM forcetest WHERE a = 1;
    | NULL
 (1 row)
 
--- should succeed with no effect ("b" remains an empty string, "c" remains NULL)
+-- should succeed, FORCE_NULL and FORCE_NOT_NULL can be both specified
 BEGIN;
-COPY forcetest (a, b, c) FROM STDIN WITH (FORMAT csv, FORCE_NOT_NULL(b), FORCE_NULL(c));
+COPY forcetest (a, b, c, d) FROM STDIN WITH (FORMAT csv, FORCE_NOT_NULL(c,d), FORCE_NULL(c,d));
 COMMIT;
-SELECT b, c FROM forcetest WHERE a = 2;
+SELECT c, d FROM forcetest WHERE a = 2;
- b |  c   
+ c |  d   
 ---+------
    | NULL
 (1 row)

src/test/regress/sql/copy2.sql

@@ -271,7 +271,6 @@ SELECT * FROM vistest;
 COMMIT;
 SELECT * FROM vistest;
 -- Test FORCE_NOT_NULL and FORCE_NULL options
--- should succeed with "b" set to an empty string and "c" set to NULL
 CREATE TEMP TABLE forcetest (
     a INT NOT NULL,
     b TEXT NOT NULL,
@@ -280,19 +279,20 @@ CREATE TEMP TABLE forcetest (
     e TEXT
 );
 \pset null NULL
+-- should succeed with no effect ("b" remains an empty string, "c" remains NULL)
 BEGIN;
 COPY forcetest (a, b, c) FROM STDIN WITH (FORMAT csv, FORCE_NOT_NULL(b), FORCE_NULL(c));
 1,,""
 \.
 COMMIT;
 SELECT b, c FROM forcetest WHERE a = 1;
--- should succeed with no effect ("b" remains an empty string, "c" remains NULL)
+-- should succeed, FORCE_NULL and FORCE_NOT_NULL can be both specified
 BEGIN;
-COPY forcetest (a, b, c) FROM STDIN WITH (FORMAT csv, FORCE_NOT_NULL(b), FORCE_NULL(c));
+COPY forcetest (a, b, c, d) FROM STDIN WITH (FORMAT csv, FORCE_NOT_NULL(c,d), FORCE_NULL(c,d));
-2,,""
+2,'a',,""
 \.
 COMMIT;
-SELECT b, c FROM forcetest WHERE a = 2;
+SELECT c, d FROM forcetest WHERE a = 2;
 -- should fail with not-null constraint violation
 BEGIN;
 COPY forcetest (a, b, c) FROM STDIN WITH (FORMAT csv, FORCE_NULL(b), FORCE_NOT_NULL(c));