0002-Improve-error-report-for-PL-pgSQL-reserved-word-used.patch

From 03c62909c4eac5bcc7c7e07d221656fd3c406b33 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 25 Apr 2025 17:22:27 -0400
Subject: [PATCH 2/3] Improve error report for PL/pgSQL reserved word used as a
 field name.

The current code in resolve_column_ref (dating to commits 01f7d2990
and fe24d7816) believes that not finding a RECFIELD datum is a
can't-happen case, in consequence of which I didn't spend a whole lot
of time considering what to do if it did happen.  But it turns out
that it *can* happen if the would-be field name is a fully-reserved
PL/pgSQL keyword.  Change the error message to describe that
situation, and add a test case demonstrating it.

This might need further refinement if anyone can find other ways to
trigger a failure here; but without an example it's not clear what
other error to throw.
---
 src/pl/plpgsql/src/expected/plpgsql_misc.out | 22 ++++++++++++++++++++
 src/pl/plpgsql/src/pl_comp.c                 | 19 ++++++++++-------
 src/pl/plpgsql/src/sql/plpgsql_misc.sql      | 16 ++++++++++++++
 3 files changed, 50 insertions(+), 7 deletions(-)

diff --git a/src/pl/plpgsql/src/expected/plpgsql_misc.out b/src/pl/plpgsql/src/expected/plpgsql_misc.out
index a6511df08ec..7c87029783a 100644
--- a/src/pl/plpgsql/src/expected/plpgsql_misc.out
+++ b/src/pl/plpgsql/src/expected/plpgsql_misc.out
@@ -65,3 +65,25 @@ do $$ declare x public.foo%rowtype; begin end $$;
 ERROR:  relation "public.foo" does not exist
 CONTEXT:  compilation of PL/pgSQL function "inline_code_block" near line 1
 do $$ declare x public.misc_table%rowtype; begin end $$;
+-- Test handling of a reserved word as a record field name
+do $$ declare r record;
+begin
+  select 1 as x, 2 as foreach into r;
+  raise notice 'r.x = %', r.x;
+  raise notice 'r.foreach = %', r.foreach;
+end $$;
+NOTICE:  r.x = 1
+ERROR:  field name "foreach" is a reserved key word
+LINE 1: r.foreach
+        ^
+HINT:  Use double quotes to quote it.
+QUERY:  r.foreach
+CONTEXT:  PL/pgSQL function inline_code_block line 5 at RAISE
+do $$ declare r record;
+begin
+  select 1 as x, 2 as foreach into r;
+  raise notice 'r.x = %', r.x;
+  raise notice 'r."foreach" = %', r."foreach";
+end $$;
+NOTICE:  r.x = 1
+NOTICE:  r."foreach" = 2
diff --git a/src/pl/plpgsql/src/pl_comp.c b/src/pl/plpgsql/src/pl_comp.c
index b80c59447fb..ee961425a5b 100644
--- a/src/pl/plpgsql/src/pl_comp.c
+++ b/src/pl/plpgsql/src/pl_comp.c
@@ -1211,17 +1211,22 @@ resolve_column_ref(ParseState *pstate, PLpgSQL_expr *expr,
 				}
 
 				/*
-				 * We should not get here, because a RECFIELD datum should
-				 * have been built at parse time for every possible qualified
-				 * reference to fields of this record.  But if we do, handle
-				 * it like field-not-found: throw error or return NULL.
+				 * Ideally we'd never get here, because a RECFIELD datum
+				 * should have been built at parse time for every qualified
+				 * reference to a field of this record that appears in the
+				 * source text.  However, plpgsql_yylex will not build such a
+				 * datum unless the field name lexes as token type IDENT.
+				 * Hence, if the would-be field name is a PL/pgSQL reserved
+				 * word, we lose.  Assume that that's what happened and tell
+				 * the user to quote it, unless the caller prefers we just
+				 * return NULL.
 				 */
 				if (error_if_no_field)
 					ereport(ERROR,
-							(errcode(ERRCODE_UNDEFINED_COLUMN),
-							 errmsg("record \"%s\" has no field \"%s\"",
-									(nnames_field == 1) ? name1 : name2,
+							(errcode(ERRCODE_SYNTAX_ERROR),
+							 errmsg("field name \"%s\" is a reserved key word",
 									colname),
+							 errhint("Use double quotes to quote it."),
 							 parser_errposition(pstate, cref->location)));
 			}
 			break;
diff --git a/src/pl/plpgsql/src/sql/plpgsql_misc.sql b/src/pl/plpgsql/src/sql/plpgsql_misc.sql
index d3a7f703a75..4c31b9d11fc 100644
--- a/src/pl/plpgsql/src/sql/plpgsql_misc.sql
+++ b/src/pl/plpgsql/src/sql/plpgsql_misc.sql
@@ -37,3 +37,19 @@ do $$ declare x foo.bar%rowtype; begin end $$;
 do $$ declare x foo.bar.baz%rowtype; begin end $$;
 do $$ declare x public.foo%rowtype; begin end $$;
 do $$ declare x public.misc_table%rowtype; begin end $$;
+
+-- Test handling of a reserved word as a record field name
+
+do $$ declare r record;
+begin
+  select 1 as x, 2 as foreach into r;
+  raise notice 'r.x = %', r.x;
+  raise notice 'r.foreach = %', r.foreach;
+end $$;
+
+do $$ declare r record;
+begin
+  select 1 as x, 2 as foreach into r;
+  raise notice 'r.x = %', r.x;
+  raise notice 'r."foreach" = %', r."foreach";
+end $$;
-- 
2.49.0