/*
* GetOrEstablishConnection returns a PGconn which can be used to execute
* queries on a remote PostgreSQL server. If no suitable connection to the
* specified node on the specified port yet exists, the function establishes
* a new connection and adds it to the connection cache before returning it.
*
* Returned connections are guaranteed to be in the CONNECTION_OK state. If the
* requested connection cannot be established, or if it was previously created
* but is now in an unrecoverable bad state, this function returns NULL.
*
* This function throws an error if a hostname over 255 characters is provided.
*/
PGconn *
GetOrEstablishConnection(char *nodeName, int32 nodePort)
{
PGconn *connection = NULL;
NodeConnectionKey nodeConnectionKey;
NodeConnectionEntry *nodeConnectionEntry = NULL;
bool entryFound = false;
bool needNewConnection = true;
char *userName = CurrentUserName();
/* check input */
if (strnlen(nodeName, MAX_NODE_LENGTH + 1) > MAX_NODE_LENGTH)
{
ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("hostname exceeds the maximum length of %d",
MAX_NODE_LENGTH)));
}
/* if first call, initialize the connection hash */
if (NodeConnectionHash == NULL)
{
NodeConnectionHash = CreateNodeConnectionHash();
}
memset(&nodeConnectionKey, 0, sizeof(nodeConnectionKey));
strncpy(nodeConnectionKey.nodeName, nodeName, MAX_NODE_LENGTH);
nodeConnectionKey.nodePort = nodePort;
strncpy(nodeConnectionKey.nodeUser, userName, NAMEDATALEN);
nodeConnectionEntry = hash_search(NodeConnectionHash, &nodeConnectionKey,
HASH_FIND, &entryFound);
if (entryFound)
{
connection = nodeConnectionEntry->connection;
if (PQstatus(connection) == CONNECTION_OK)
{
needNewConnection = false;
}
else
{
PurgeConnection(connection);
}
}
if (needNewConnection)
{
connection = ConnectToNode(nodeName, nodePort, nodeConnectionKey.nodeUser);
if (connection != NULL)
{
nodeConnectionEntry = hash_search(NodeConnectionHash, &nodeConnectionKey,
HASH_ENTER, &entryFound);
nodeConnectionEntry->connection = connection;
}
}
return connection;
}
/*
* GetConnection returns a PGconn which can be used to execute queries on a
* remote PostgreSQL server. If no suitable connection to the specified node on
* the specified port yet exists, the function establishes a new connection and
* returns that.
*
* Returned connections are guaranteed to be in the CONNECTION_OK state. If the
* requested connection cannot be established, or if it was previously created
* but is now in an unrecoverable bad state, this function returns NULL.
*
* This function throws an error if a hostname over 255 characters is provided.
*/
PGconn *
GetConnection(char *nodeName, int32 nodePort)
{
PGconn *connection = NULL;
NodeConnectionKey nodeConnectionKey;
NodeConnectionEntry *nodeConnectionEntry = NULL;
bool entryFound = false;
bool needNewConnection = true;
/* check input */
if (strnlen(nodeName, MAX_NODE_LENGTH + 1) > MAX_NODE_LENGTH)
{
ereport(ERROR, (errmsg("hostnames may not exceed 255 characters")));
}
/* if first call, initialize the connection hash */
if (NodeConnectionHash == NULL)
{
NodeConnectionHash = CreateNodeConnectionHash();
}
memset(&nodeConnectionKey, 0, sizeof(nodeConnectionKey));
strncpy(nodeConnectionKey.nodeName, nodeName, MAX_NODE_LENGTH);
nodeConnectionKey.nodePort = nodePort;
nodeConnectionEntry = hash_search(NodeConnectionHash, &nodeConnectionKey,
HASH_FIND, &entryFound);
if (entryFound)
{
connection = nodeConnectionEntry->connection;
if (PQstatus(connection) == CONNECTION_OK)
{
needNewConnection = false;
}
else
{
PurgeConnection(connection);
}
}
if (needNewConnection)
{
StringInfo nodePortString = makeStringInfo();
appendStringInfo(nodePortString, "%d", nodePort);
connection = ConnectToNode(nodeName, nodePortString->data);
if (connection != NULL)
{
nodeConnectionEntry = hash_search(NodeConnectionHash, &nodeConnectionKey,
HASH_ENTER, &entryFound);
nodeConnectionEntry->connection = connection;
}
}
return connection;
}
