From a6be6d86457a0b5dc982a0d4c7128a510313506d Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 25 Feb 2016 22:24:53 +0000
Subject: Reuse prepared statements

---
 libpqpp/pq-connection.h      |  5 +++++
 libpqpp/pq-modifycommand.cpp | 23 ++++++++++++-----------
 libpqpp/pq-modifycommand.h   |  6 +++---
 libpqpp/unittests/testpq.cpp | 16 ++++++++++++++++
 4 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/libpqpp/pq-connection.h b/libpqpp/pq-connection.h
index 59b200c..1e9f265 100644
--- a/libpqpp/pq-connection.h
+++ b/libpqpp/pq-connection.h
@@ -2,6 +2,7 @@
 #define PQ_CONNECTION_H
 
 #include <connection.h>
+#include <set>
 #include <libpq-fe.h>
 #include <visibility.h>
 #include "pq-error.h"
@@ -14,6 +15,9 @@ namespace PQ {
 
 	class DLL_PUBLIC Connection : public DB::Connection {
 		public:
+			typedef std::hash<std::string>::result_type StatementHash;
+			typedef std::map<StatementHash, std::string> PreparedStatements;
+
 			Connection(const std::string & info);
 			~Connection();
 
@@ -38,6 +42,7 @@ namespace PQ {
 			void checkResultFree(PGresult * res, int expected, int alternative = -1) const;
 
 			PGconn * conn;
+			PreparedStatements preparedStatements;
 
 		private:
 			static bool checkResultInt(PGresult * res, int expected, int alternative);
diff --git a/libpqpp/pq-modifycommand.cpp b/libpqpp/pq-modifycommand.cpp
index 4c4ca0c..e59908e 100644
--- a/libpqpp/pq-modifycommand.cpp
+++ b/libpqpp/pq-modifycommand.cpp
@@ -7,7 +7,7 @@ PQ::ModifyCommand::ModifyCommand(Connection * conn, const std::string & sql, uns
 	DB::Command(sql),
 	DB::ModifyCommand(sql),
 	PQ::Command(conn, sql, no),
-	prepared(false)
+	hash(std::hash<std::string>()(sql))
 {
 }
 
@@ -15,24 +15,25 @@ PQ::ModifyCommand::~ModifyCommand()
 {
 }
 
-void
+PQ::Connection::PreparedStatements::const_iterator
 PQ::ModifyCommand::prepare() const
 {
-	if (!prepared) {
-		std::string psql;
-		psql.reserve(sql.length() + 20);
-		prepareSql(psql, sql);
-		c->checkResultFree(PQprepare(
-					c->conn, stmntName.c_str(), psql.c_str(), values.size(), NULL), PGRES_COMMAND_OK);
-		prepared = true;
+	auto i = c->preparedStatements.find(hash);
+	if (i != c->preparedStatements.end()) {
+		return i;
 	}
+	std::string psql;
+	psql.reserve(sql.length() + 20);
+	prepareSql(psql, sql);
+	c->checkResultFree(PQprepare(
+				c->conn, stmntName.c_str(), psql.c_str(), values.size(), NULL), PGRES_COMMAND_OK);
+	return c->preparedStatements.insert({hash, stmntName}).first;
 }
 
 unsigned int
 PQ::ModifyCommand::execute(bool anc)
 {
-	prepare();
-	PGresult * res = PQexecPrepared(c->conn, stmntName.c_str(), values.size(), &values.front(), &lengths.front(), NULL, 0);
+	PGresult * res = PQexecPrepared(c->conn, prepare()->second.c_str(), values.size(), &values.front(), &lengths.front(), NULL, 0);
 	c->checkResult(res, PGRES_COMMAND_OK, PGRES_TUPLES_OK);
 	unsigned int rows = atoi(PQcmdTuples(res));
 	PQclear(res);
diff --git a/libpqpp/pq-modifycommand.h b/libpqpp/pq-modifycommand.h
index 5f48074..33fd333 100644
--- a/libpqpp/pq-modifycommand.h
+++ b/libpqpp/pq-modifycommand.h
@@ -3,9 +3,9 @@
 
 #include <modifycommand.h>
 #include "pq-command.h"
+#include "pq-connection.h"
 
 namespace PQ {
-	class Connection;
 	class ModifyCommand : public DB::ModifyCommand, public Command {
 		public:
 			ModifyCommand(Connection *, const std::string & sql, unsigned int no);
@@ -14,8 +14,8 @@ namespace PQ {
 			unsigned int execute(bool) override;
 
 		private:
-			void prepare() const;
-			mutable bool prepared;
+			Connection::PreparedStatements::const_iterator prepare() const;
+			const Connection::StatementHash hash;
 	};
 }
 
diff --git a/libpqpp/unittests/testpq.cpp b/libpqpp/unittests/testpq.cpp
index 80757db..3d8c804 100644
--- a/libpqpp/unittests/testpq.cpp
+++ b/libpqpp/unittests/testpq.cpp
@@ -262,6 +262,22 @@ BOOST_AUTO_TEST_CASE( reconnectInTx )
 	delete rok;
 }
 
+BOOST_AUTO_TEST_CASE( statementReuse )
+{
+	auto ro = DB::MockDatabase::openConnectionTo("pqmock");
+	auto pqconn = dynamic_cast<PQ::Connection *>(ro);
+	BOOST_REQUIRE_EQUAL(pqconn->preparedStatements.size(), 0);
+	for (int y = 0; y < 4; y += 1) {
+		auto m1 = ro->modify("INSERT INTO test(id) VALUES(?)");
+		for (int x = 0; x < 4; x += 1) {
+			m1->bindParamI(0, x);
+			m1->execute();
+		}
+	}
+	BOOST_REQUIRE_EQUAL(pqconn->preparedStatements.size(), 1);
+	delete ro;
+}
+
 BOOST_AUTO_TEST_SUITE_END();
 
 BOOST_AUTO_TEST_CASE( connfail )
-- 
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