Show ignored constants as "$N" rather than "?" in pg_stat_statements.

The trouble with the original choice here is that "?" is a valid (and
indeed used) operator name, so that you could end up with ambiguous
statement texts like "SELECT ? ? ?".  With this patch, you instead
see "SELECT $1 ? $2", which seems significantly more readable.
The numbers used for this purpose begin after the last actual $N parameter
in the particular query.  The conflict with external parameters has its own
potential for confusion of course, but it was agreed to be an improvement
over the previous behavior.

Lukas Fittl

Discussion: https://postgr.es/m/CAP53PkxeaCuwYmF-A4J5z2-qk5fYFo5_NH3gpXGJJBxv1DMwEw@mail.gmail.com

contrib/pg_stat_statements/sql/pg_stat_statements.sql

@@ -37,12 +37,20 @@ SELECT :add + 1 + 1 AS "add" \gset
 -- set operator
 SELECT 1 AS i UNION SELECT 2 ORDER BY i;
 
+-- ? operator
+select '{"a":1, "b":2}'::jsonb ? 'b';
+
 -- cte
 WITH t(f) AS (
   VALUES (1.0), (2.0)
 )
   SELECT f FROM t ORDER BY f;
 
+-- prepared statement with parameter
+PREPARE pgss_test (int) AS SELECT $1, 'test' LIMIT 1;
+EXECUTE pgss_test(1);
+DEALLOCATE pgss_test;
+
 SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
 
 --
@@ -51,7 +59,7 @@ SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
 SELECT pg_stat_statements_reset();
 
 -- utility "create table" should not be shown
-CREATE TABLE test (a int, b char(20));
+CREATE TEMP TABLE test (a int, b char(20));
 
 INSERT INTO test VALUES(generate_series(1, 10), 'aaa');
 UPDATE test SET b = 'bbb' WHERE a > 7;
@@ -74,6 +82,9 @@ UPDATE test SET b = '555' WHERE a = 5 \;
 UPDATE test SET b = '666' WHERE a = 6 \;
 COMMIT ;
 
+-- many INSERT values
+INSERT INTO test (a, b) VALUES (1, 'a'), (2, 'b'), (3, 'c');
+
 -- SELECT with constants
 SELECT * FROM test WHERE a > 5 ORDER BY a ;
 
@@ -85,6 +96,9 @@ SELECT *
 -- SELECT without constants
 SELECT * FROM test ORDER BY a;
 
+-- SELECT with IN clause
+SELECT * FROM test WHERE a IN (1, 2, 3, 4, 5);
+
 SELECT query, calls, rows FROM pg_stat_statements ORDER BY query COLLATE "C";
 
 --