Stop using spelling "nonexistant".

The documentation used "nonexistent" exclusively, and the source tree
used it three times as often as "nonexistant".

src/test/regress/expected/alter_table.out

@@ -1349,7 +1349,7 @@ delete from atacc1;
 -- try dropping a non-existent column, should fail
 alter table atacc1 drop bar;
 ERROR:  column "bar" of relation "atacc1" does not exist
--- try removing an oid column, should succeed (as it's nonexistant)
+-- try removing an oid column, should succeed (as it's nonexistent)
 alter table atacc1 SET WITHOUT OIDS;
 -- try adding an oid column, should fail (not supported)
 alter table atacc1 SET WITH OIDS;
@@ -3432,8 +3432,8 @@ LINE 1: ...list_parted ATTACH PARTITION fail_part FOR VALUES FROM (1) T...
                                                              ^
 DROP TABLE fail_part;
 -- check that the table being attached exists
-ALTER TABLE list_parted ATTACH PARTITION nonexistant FOR VALUES IN (1);
-ERROR:  relation "nonexistant" does not exist
+ALTER TABLE list_parted ATTACH PARTITION nonexistent FOR VALUES IN (1);
+ERROR:  relation "nonexistent" does not exist
 -- check ownership of the source table
 CREATE ROLE regress_test_me;
 CREATE ROLE regress_test_not_me;

src/test/regress/expected/create_am.out

@@ -111,7 +111,7 @@ NOTICE:  drop cascades to index grect2ind2
 SET default_table_access_method = '';
 ERROR:  invalid value for parameter "default_table_access_method": ""
 DETAIL:  default_table_access_method cannot be empty.
--- prevent nonexistant values
+-- prevent nonexistent values
 SET default_table_access_method = 'I do not exist AM';
 ERROR:  invalid value for parameter "default_table_access_method": "I do not exist AM"
 DETAIL:  Table access method "I do not exist AM" does not exist.
@@ -274,7 +274,7 @@ ORDER BY 3, 1, 2;
 
 -- don't want to keep those tables, nor the default
 ROLLBACK;
--- Third, check that we can neither create a table using a nonexistant
+-- Third, check that we can neither create a table using a nonexistent
 -- AM, nor using an index AM
 CREATE TABLE i_am_a_failure() USING "";
 ERROR:  zero-length delimited identifier at or near """"

src/test/regress/expected/rowtypes.out

@@ -1197,9 +1197,9 @@ ERROR:  column "ctid" not found in data type compositetable
 LINE 1: SELECT (d).ctid FROM (SELECT compositetable AS d FROM compos...
                 ^
 -- accessing non-existing column in NULL datum errors out
-SELECT (NULL::compositetable).nonexistant;
-ERROR:  column "nonexistant" not found in data type compositetable
-LINE 1: SELECT (NULL::compositetable).nonexistant;
+SELECT (NULL::compositetable).nonexistent;
+ERROR:  column "nonexistent" not found in data type compositetable
+LINE 1: SELECT (NULL::compositetable).nonexistent;
                 ^
 -- existing column in a NULL composite yield NULL
 SELECT (NULL::compositetable).a;

src/test/regress/expected/stats_ext.out

@@ -35,8 +35,8 @@ CREATE STATISTICS tst FROM sometab;
 ERROR:  syntax error at or near "FROM"
 LINE 1: CREATE STATISTICS tst FROM sometab;
                               ^
-CREATE STATISTICS tst ON a, b FROM nonexistant;
-ERROR:  relation "nonexistant" does not exist
+CREATE STATISTICS tst ON a, b FROM nonexistent;
+ERROR:  relation "nonexistent" does not exist
 CREATE STATISTICS tst ON a, b FROM pg_class;
 ERROR:  column "a" does not exist
 CREATE STATISTICS tst ON relname, relname, relnatts FROM pg_class;

src/test/regress/sql/alter_table.sql

@@ -973,7 +973,7 @@ delete from atacc1;
 -- try dropping a non-existent column, should fail
 alter table atacc1 drop bar;
 
--- try removing an oid column, should succeed (as it's nonexistant)
+-- try removing an oid column, should succeed (as it's nonexistent)
 alter table atacc1 SET WITHOUT OIDS;
 
 -- try adding an oid column, should fail (not supported)
@@ -2152,7 +2152,7 @@ ALTER TABLE list_parted ATTACH PARTITION fail_part FOR VALUES FROM (1) TO (10);
 DROP TABLE fail_part;
 
 -- check that the table being attached exists
-ALTER TABLE list_parted ATTACH PARTITION nonexistant FOR VALUES IN (1);
+ALTER TABLE list_parted ATTACH PARTITION nonexistent FOR VALUES IN (1);
 
 -- check ownership of the source table
 CREATE ROLE regress_test_me;

src/test/regress/sql/create_am.sql

@@ -80,7 +80,7 @@ DROP ACCESS METHOD gist2 CASCADE;
 -- prevent empty values
 SET default_table_access_method = '';
 
--- prevent nonexistant values
+-- prevent nonexistent values
 SET default_table_access_method = 'I do not exist AM';
 
 -- prevent setting it to an index AM
@@ -198,7 +198,7 @@ ORDER BY 3, 1, 2;
 -- don't want to keep those tables, nor the default
 ROLLBACK;
 
--- Third, check that we can neither create a table using a nonexistant
+-- Third, check that we can neither create a table using a nonexistent
 -- AM, nor using an index AM
 CREATE TABLE i_am_a_failure() USING "";
 CREATE TABLE i_am_a_failure() USING i_do_not_exist_am;

src/test/regress/sql/rowtypes.sql

@@ -486,7 +486,7 @@ SELECT (d).a, (d).b FROM (SELECT compositetable AS d FROM compositetable) s;
 SELECT (d).ctid FROM (SELECT compositetable AS d FROM compositetable) s;
 
 -- accessing non-existing column in NULL datum errors out
-SELECT (NULL::compositetable).nonexistant;
+SELECT (NULL::compositetable).nonexistent;
 -- existing column in a NULL composite yield NULL
 SELECT (NULL::compositetable).a;
 -- oids can't be accessed in composite types (error)

src/test/regress/sql/stats_ext.sql

@@ -29,7 +29,7 @@ $$;
 CREATE STATISTICS tst;
 CREATE STATISTICS tst ON a, b;
 CREATE STATISTICS tst FROM sometab;
-CREATE STATISTICS tst ON a, b FROM nonexistant;
+CREATE STATISTICS tst ON a, b FROM nonexistent;
 CREATE STATISTICS tst ON a, b FROM pg_class;
 CREATE STATISTICS tst ON relname, relname, relnatts FROM pg_class;
 CREATE STATISTICS tst ON relnatts + relpages FROM pg_class;