Re-implement pl/pgsql's expression and assignment parsing.

Invent new RawParseModes that allow the core grammar to handle
pl/pgsql expressions and assignments directly, and thereby get rid
of a lot of hackery in pl/pgsql's parser.  This moves a good deal
of knowledge about pl/pgsql into the core code: notably, we have to
invent a CoercionContext that matches pl/pgsql's (rather dubious)
historical behavior for assignment coercions.  That's getting away
from the original idea of pl/pgsql as an arm's-length extension of
the core, but really we crossed that bridge a long time ago.

The main advantage of doing this is that we can now use the core
parser to generate FieldStore and/or SubscriptingRef nodes to handle
assignments to pl/pgsql variables that are records or arrays.  That
fixes a number of cases that had never been implemented in pl/pgsql
assignment, such as nested records and array slicing, and it allows
pl/pgsql assignment to support the datatype-specific subscripting
behaviors introduced in commit c7aba7c14.

There are cosmetic benefits too: when a syntax error occurs in a
pl/pgsql expression, the error report no longer includes the confusing
"SELECT" keyword that used to get prefixed to the expression text.
Also, there seem to be some small speed gains.

Discussion: https://postgr.es/m/4165684.1607707277@sss.pgh.pa.us

1 files changed, 18 insertions, 18 deletions

diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index d55006d8c95..0c6c9ba1f59 100644
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -1761,10 +1761,10 @@ select f1(42) as int, f1(4.5) as num;
 
 select f1(point(3,4));  -- fail for lack of + operator
 ERROR:  operator does not exist: point + integer
-LINE 1: SELECT x + 1
-                 ^
+LINE 1: x + 1
+          ^
 HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
-QUERY:  SELECT x + 1
+QUERY:  x + 1
 CONTEXT:  PL/pgSQL function f1(anyelement) line 3 at RETURN
 drop function f1(x anyelement);
 create function f1(x anyelement) returns anyarray as $$
@@ -2361,7 +2361,7 @@ begin
 end $$ language plpgsql;
 select namedparmcursor_test7();
 ERROR:  division by zero
-CONTEXT:  SQL statement "SELECT 42/0 AS p1, 77 AS p2;"
+CONTEXT:  SQL expression "42/0 AS p1, 77 AS p2"
 PL/pgSQL function namedparmcursor_test7() line 6 at OPEN
 -- check that line comments work correctly within the argument list (there
 -- is some special handling of this case in the code: the newline after the
@@ -2574,9 +2574,9 @@ end; $$ language plpgsql;
 -- blocks
 select excpt_test1();
 ERROR:  column "sqlstate" does not exist
-LINE 1: SELECT sqlstate
-               ^
-QUERY:  SELECT sqlstate
+LINE 1: sqlstate
+        ^
+QUERY:  sqlstate
 CONTEXT:  PL/pgSQL function excpt_test1() line 3 at RAISE
 create function excpt_test2() returns void as $$
 begin
@@ -2589,9 +2589,9 @@ end; $$ language plpgsql;
 -- should fail
 select excpt_test2();
 ERROR:  column "sqlstate" does not exist
-LINE 1: SELECT sqlstate
-               ^
-QUERY:  SELECT sqlstate
+LINE 1: sqlstate
+        ^
+QUERY:  sqlstate
 CONTEXT:  PL/pgSQL function excpt_test2() line 5 at RAISE
 create function excpt_test3() returns void as $$
 begin
@@ -4467,11 +4467,11 @@ end
 $$;
 select fail();
 ERROR:  division by zero
-CONTEXT:  SQL statement "SELECT 1/0"
+CONTEXT:  SQL expression "1/0"
 PL/pgSQL function fail() line 3 at RETURN
 select fail();
 ERROR:  division by zero
-CONTEXT:  SQL statement "SELECT 1/0"
+CONTEXT:  SQL expression "1/0"
 PL/pgSQL function fail() line 3 at RETURN
 drop function fail();
 -- Test handling of string literals.
@@ -4497,10 +4497,10 @@ HINT:  Use the escape string syntax for backslashes, e.g., E'\\'.
 select strtest();
 NOTICE:  foo\bar!baz
 WARNING:  nonstandard use of \\ in a string literal
-LINE 1: SELECT 'foo\\bar\041baz'
-               ^
+LINE 1: 'foo\\bar\041baz'
+        ^
 HINT:  Use the escape string syntax for backslashes, e.g., E'\\'.
-QUERY:  SELECT 'foo\\bar\041baz'
+QUERY:  'foo\\bar\041baz'
    strtest   
 -------------
  foo\bar!baz
@@ -5621,9 +5621,9 @@ ALTER TABLE alter_table_under_transition_tables
 UPDATE alter_table_under_transition_tables
   SET id = id;
 ERROR:  column "name" does not exist
-LINE 1: SELECT (SELECT string_agg(id || '=' || name, ',') FROM d)
-                                               ^
-QUERY:  SELECT (SELECT string_agg(id || '=' || name, ',') FROM d)
+LINE 1: (SELECT string_agg(id || '=' || name, ',') FROM d)
+                                        ^
+QUERY:  (SELECT string_agg(id || '=' || name, ',') FROM d)
 CONTEXT:  PL/pgSQL function alter_table_under_transition_tables_upd_func() line 3 at RAISE
 --
 -- Test multiple reference to a transition table