Evaluate enforce_autocommit_on_reads on PS #899

Variable mysql-enforce_autocommit_on_reads wasn't evaluate for prepared statements.

include/MySQL_PreparedStatement.h

@@ -62,6 +62,7 @@ class MySQL_STMT_Global_info {
 		int timeout;
 		int delay;
 	} properties;
+	bool is_select_NOT_for_update;
 	MYSQL_BIND **params; // seems unused (?)
 	MySQL_STMT_Global_info(uint32_t id, unsigned int h, char *u, char *s, char *q, unsigned int ql, MYSQL_STMT *stmt, uint64_t _h);
 	~MySQL_STMT_Global_info();

lib/MySQL_PreparedStatement.cpp

@@ -322,6 +322,22 @@ MySQL_STMT_Global_info::MySQL_STMT_Global_info(uint32_t id, unsigned int h, char
 		compute_hash();
 	}
 
+	is_select_NOT_for_update=false;
+	{ // see bug #899 . Most of the code is borrowed from Query_Info::is_select_NOT_for_update()
+		if (ql>=7) {
+			if (strncasecmp(q,(char *)"SELECT ",7)==0) { // is a SELECT
+				is_select_NOT_for_update=true;
+				if (ql>=17) {
+					char *p=(char *)q;
+					p+=ql-11;
+					if (strncasecmp(p," FOR UPDATE",11)==0) { // is a SELECT FOR UPDATE
+						is_select_NOT_for_update=false;
+					}
+				}
+			}
+		}
+	}
+
 	// set default properties:
 	properties.cache_ttl=-1;
 	properties.timeout=-1;

lib/MySQL_Session.cpp

@@ -187,6 +187,9 @@ char * Query_Info::get_digest_text() {
 }
 
 bool Query_Info::is_select_NOT_for_update() {
+	if (stmt_info) { // we are processing a prepared statement. We already have the information
+		return stmt_info->is_select_NOT_for_update;
+	}
 	// to avoid an expensive strlen() on the digest_text, we consider only the real query
 	if (QueryPointer==NULL) {
 		return false;