Add backend-only appendStringInfoStringQuoted

This provides a mechanism to emit literal values in informative
messages, such as query parameters.  The new code is more complex than
what it replaces, primarily because it wants to be more efficient.
It also has the (currently unused) additional optional capability of
specifying a maximum size to print.

The new function lives out of common/stringinfo.c so that frontend users
of that file need not pull in unnecessary multibyte-encoding support
code.

Author: Álvaro Herrera and Alexey Bashtanov, after a suggestion from Andres Freund
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/20190920203905.xkv5udsd5dxfs6tr@alap3.anarazel.de

2 files changed, 27 insertions, 0 deletions

diff --git a/src/test/regress/expected/plpgsql.out b/src/test/regress/expected/plpgsql.out
index e85b29455e5..cd2c79f4d50 100644
--- a/src/test/regress/expected/plpgsql.out
+++ b/src/test/regress/expected/plpgsql.out
@@ -2656,6 +2656,20 @@ create or replace function stricttest() returns void as $$
 declare
 x record;
 p1 int := 2;
+p3 text := $a$'Valame Dios!' dijo Sancho; 'no le dije yo a vuestra merced que mirase bien lo que hacia?'$a$;
+begin
+  -- no rows
+  select * from foo where f1 = p1 and f1::text = p3 into strict x;
+  raise notice 'x.f1 = %, x.f2 = %', x.f1, x.f2;
+end$$ language plpgsql;
+select stricttest();
+ERROR:  query returned no rows
+DETAIL:  parameters: p1 = '2', p3 = '''Valame Dios!'' dijo Sancho; ''no le dije yo a vuestra merced que mirase bien lo que hacia?'''
+CONTEXT:  PL/pgSQL function stricttest() line 8 at SQL statement
+create or replace function stricttest() returns void as $$
+declare
+x record;
+p1 int := 2;
 p3 text := 'foo';
 begin
   -- too many rows
diff --git a/src/test/regress/sql/plpgsql.sql b/src/test/regress/sql/plpgsql.sql
index 70deadfbea2..d841d8c0f97 100644
--- a/src/test/regress/sql/plpgsql.sql
+++ b/src/test/regress/sql/plpgsql.sql
@@ -2284,6 +2284,19 @@ create or replace function stricttest() returns void as $$
 declare
 x record;
 p1 int := 2;
+p3 text := $a$'Valame Dios!' dijo Sancho; 'no le dije yo a vuestra merced que mirase bien lo que hacia?'$a$;
+begin
+  -- no rows
+  select * from foo where f1 = p1 and f1::text = p3 into strict x;
+  raise notice 'x.f1 = %, x.f2 = %', x.f1, x.f2;
+end$$ language plpgsql;
+
+select stricttest();
+
+create or replace function stricttest() returns void as $$
+declare
+x record;
+p1 int := 2;
 p3 text := 'foo';
 begin
   -- too many rows