From 08b7d094fd66243a9e945beaf46c130291cd656e Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Tue, 2 Jun 2015 01:42:13 +0100
Subject: Prebuild (once) SQL for cursor operations. Don't open another
 transaction. Don't make another fetch to the DB if the previous read was
 short anyway. Add bulk load and bulk read tests.

---
 libpqpp/selectcommand.cpp | 85 +++++++++++++++++++++++++++++++----------------
 1 file changed, 57 insertions(+), 28 deletions(-)

(limited to 'libpqpp/selectcommand.cpp')

diff --git a/libpqpp/selectcommand.cpp b/libpqpp/selectcommand.cpp
index 359cdfd..afb8c1b 100644
--- a/libpqpp/selectcommand.cpp
+++ b/libpqpp/selectcommand.cpp
@@ -11,7 +11,11 @@ PQ::SelectCommand::SelectCommand(const Connection * conn, const std::string & sq
 	txOpened(false),
 	nTuples(0),
 	tuple(0),
-	execRes(NULL)
+	fTuples(35),
+	execRes(NULL),
+	s_declare(mkdeclare()),
+	s_fetch(mkfetch()),
+	s_close(mkclose())
 {
 }
 
@@ -21,42 +25,66 @@ PQ::SelectCommand::~SelectCommand()
 		c->commitTx();
 	}
 	if (executed) {
-		PQclear(PQexec(c->conn, ("CLOSE " + stmntName).c_str()));
+		PQclear(PQexec(c->conn, s_close.c_str()));
 		if (execRes) {
 			PQclear(execRes);
 		}
 	}
 }
 
+std::string
+PQ::SelectCommand::mkdeclare() const
+{
+	std::string psql;
+	psql.reserve(sql.length() + 40);
+	char buf[4];
+	int p = 1;
+	bool inquote = false;
+	psql += "DECLARE ";
+	psql += stmntName;
+	psql += " CURSOR FOR ";
+	for(std::string::const_iterator i = sql.begin(); i != sql.end(); ++i) {
+		if (*i == '?' && !inquote) {
+			snprintf(buf, 4, "$%d", p++);
+			psql += buf;
+		}
+		else if (*i == '\'') {
+			inquote = !inquote;
+			psql += *i;
+		}
+		else {
+			psql += *i;
+		}
+	}
+	return psql;
+}
+
+std::string
+PQ::SelectCommand::mkfetch() const
+{
+	char buf[BUFSIZ];
+	snprintf(buf, sizeof(buf), "FETCH %d IN %s", fTuples, stmntName.c_str());
+	return buf;
+}
+
+std::string
+PQ::SelectCommand::mkclose() const
+{
+	char buf[BUFSIZ];
+	snprintf(buf, sizeof(buf), "CLOSE %s", stmntName.c_str());
+	return buf;
+}
+
 void
 PQ::SelectCommand::execute()
 {
 	if (!executed) {
-		std::string psql;
-		psql.reserve(sql.length() + 40);
-		char buf[4];
-		int p = 1;
-		bool inquote = false;
-		psql += "DECLARE ";
-		psql += stmntName;
-		psql += " CURSOR FOR ";
-		for(std::string::const_iterator i = sql.begin(); i != sql.end(); ++i) {
-			if (*i == '?' && !inquote) {
-				snprintf(buf, 4, "$%d", p++);
-				psql += buf;
-			}
-			else if (*i == '\'') {
-				inquote = !inquote;
-				psql += *i;
-			}
-			else {
-				psql += *i;
-			}
+		if (!txOpened) {
+			c->beginTx();
+			txOpened = true;
 		}
-		c->beginTx();
-		txOpened = true;
 		execRes = c->checkResult(
-				PQexecParams(c->conn, psql.c_str(), values.size(), NULL, &values.front(), &lengths.front(), &formats.front(), 0),
+				PQexecParams(c->conn, s_declare.c_str(), values.size(), NULL, &values.front(), &lengths.front(), &formats.front(), 0),
 				PGRES_COMMAND_OK);
 		fetchTuples();
 		unsigned int nFields = PQnfields(execRes);
@@ -74,7 +102,7 @@ PQ::SelectCommand::fetchTuples()
 		PQclear(execRes);
 	}
 	execRes = NULL;
-	execRes = c->checkResult(PQexec(c->conn, ("FETCH 35 IN " + stmntName).c_str()), PGRES_TUPLES_OK);
+	execRes = c->checkResult(PQexec(c->conn, s_fetch.c_str()), PGRES_TUPLES_OK);
 	nTuples = PQntuples(execRes);
 	tuple = -1;
 }
@@ -83,15 +111,16 @@ bool
 PQ::SelectCommand::fetch()
 {
 	execute();
-	if (tuple >= (nTuples - 1)) {
+	if ((tuple >= (nTuples - 1)) && (nTuples == fTuples)) {
 		fetchTuples();
 	}
 	if (tuple++ < (nTuples - 1)) {
 		return true;
 	}
 	else {
-		PQclear(PQexec(c->conn, ("CLOSE " + stmntName).c_str()));
+		PQclear(PQexec(c->conn, s_close.c_str()));
 		PQclear(execRes);
+		execRes = NULL;
 		executed = false;
 		return false;
 	}
-- 
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