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, 47 insertions, 12 deletions

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index fe8e049c4c1..be265aa05a4 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -1274,15 +1274,28 @@ sendquery_cleanup:
 		pset.gsavepopt = NULL;
 	}
 
-	/* clean up after \bind */
-	if (pset.bind_flag)
+	/* clean up after extended protocol queries */
+	switch (pset.send_mode)
 	{
-		for (i = 0; i < pset.bind_nparams; i++)
-			free(pset.bind_params[i]);
-		free(pset.bind_params);
-		pset.bind_params = NULL;
-		pset.bind_flag = false;
+		case PSQL_SEND_EXTENDED_CLOSE:	/* \close */
+			free(pset.stmtName);
+			break;
+		case PSQL_SEND_EXTENDED_PARSE:	/* \parse */
+			free(pset.stmtName);
+			break;
+		case PSQL_SEND_EXTENDED_QUERY_PARAMS:	/* \bind */
+		case PSQL_SEND_EXTENDED_QUERY_PREPARED: /* \bind_named */
+			for (i = 0; i < pset.bind_nparams; i++)
+				free(pset.bind_params[i]);
+			free(pset.bind_params);
+			free(pset.stmtName);
+			pset.bind_params = NULL;
+			break;
+		case PSQL_SEND_QUERY:
+			break;
 	}
+	pset.stmtName = NULL;
+	pset.send_mode = PSQL_SEND_QUERY;
 
 	/* reset \gset trigger */
 	if (pset.gset_prefix)
@@ -1456,7 +1469,7 @@ ExecQueryAndProcessResults(const char *query,
 						   const printQueryOpt *opt, FILE *printQueryFout)
 {
 	bool		timing = pset.timing;
-	bool		success;
+	bool		success = false;
 	bool		return_early = false;
 	instr_time	before,
 				after;
@@ -1469,10 +1482,32 @@ ExecQueryAndProcessResults(const char *query,
 	else
 		INSTR_TIME_SET_ZERO(before);
 
-	if (pset.bind_flag)
-		success = PQsendQueryParams(pset.db, query, pset.bind_nparams, NULL, (const char *const *) pset.bind_params, NULL, NULL, 0);
-	else
-		success = PQsendQuery(pset.db, query);
+	switch (pset.send_mode)
+	{
+		case PSQL_SEND_EXTENDED_CLOSE:
+			success = PQsendClosePrepared(pset.db, pset.stmtName);
+			break;
+		case PSQL_SEND_EXTENDED_PARSE:
+			success = PQsendPrepare(pset.db, pset.stmtName, query, 0, NULL);
+			break;
+		case PSQL_SEND_EXTENDED_QUERY_PARAMS:
+			Assert(pset.stmtName == NULL);
+			success = PQsendQueryParams(pset.db, query,
+										pset.bind_nparams, NULL,
+										(const char *const *) pset.bind_params,
+										NULL, NULL, 0);
+			break;
+		case PSQL_SEND_EXTENDED_QUERY_PREPARED:
+			Assert(pset.stmtName != NULL);
+			success = PQsendQueryPrepared(pset.db, pset.stmtName,
+										  pset.bind_nparams,
+										  (const char *const *) pset.bind_params,
+										  NULL, NULL, 0);
+			break;
+		case PSQL_SEND_QUERY:
+			success = PQsendQuery(pset.db, query);
+			break;
+	}
 
 	if (!success)
 	{