psql: Add more meta-commands able to use the extended protocol

Currently, only unnamed prepared statement are supported by psql with
the meta-command \bind.  With only this command, it is not possible to
test named statement creation, execution or close through the extended
protocol.

This commit introduces three additional commands:
* \parse creates a prepared statement using the extended protocol,
acting as a wrapper of libpq's PQsendPrepare().
* \bind_named binds and executes an existing prepared statement using
the extended protocol, for PQsendQueryPrepared().
* \close closes an existing prepared statement using the extended
protocol, for PQsendClosePrepared().

This is going to be useful to add regression tests for the extended
query protocol, and I have some plans for that on separate threads.
Note that \bind relies on PQsendQueryParams().

The code of psql is refactored so as bind_flag is replaced by an enum in
_psqlSettings that tracks the type of libpq routine to execute, based on
the meta-command involved, with the default being PQsendQuery().  This
refactoring piece has been written by me, while Anthonin has implemented
the rest.

Author: Anthonin Bonnefoy, Michael Paquier
Reviewed-by: Aleksander Alekseev, Jelte Fennema-Nio
Discussion: https://postgr.es/m/CAO6_XqpSq0Q0kQcVLCbtagY94V2GxNP3zCnR6WnOM8WqXPK4nw@mail.gmail.com

1 files changed, 4 insertions, 0 deletions

diff --git a/src/bin/psql/help.c b/src/bin/psql/help.c
index 6f58a110748..19d20c58781 100644
--- a/src/bin/psql/help.c
+++ b/src/bin/psql/help.c
@@ -165,6 +165,9 @@ slashUsage(unsigned short int pager)
 
 	HELP0("General\n");
 	HELP0("  \\bind [PARAM]...       set query parameters\n");
+	HELP0("  \\bind_named STMT_NAME [PARAM]...\n"
+		  "                         set query parameters for an existing prepared statement\n");
+	HELP0("  \\close STMT_NAME       close an existing prepared statement\n");
 	HELP0("  \\copyright             show PostgreSQL usage and distribution terms\n");
 	HELP0("  \\crosstabview [COLUMNS] execute query and display result in crosstab\n");
 	HELP0("  \\errverbose            show most recent error message at maximum verbosity\n");
@@ -312,6 +315,7 @@ slashUsage(unsigned short int pager)
 			  "                         connect to new database (currently no connection)\n");
 	HELP0("  \\conninfo              display information about current connection\n");
 	HELP0("  \\encoding [ENCODING]   show or set client encoding\n");
+	HELP0("  \\parse STMT_NAME       create a prepared statement\n");
 	HELP0("  \\password [USERNAME]   securely change the password for a user\n");
 	HELP0("\n");