Comment 3 for bug 1046706

BrindleFly, there are some advantages to prepared statements--notably the streaming string/binary value streaming. That said, this performance issue is a major headache. I've read through the code and implemented a statement cache. This should allow us to reap the perfomance benefits of prepared queries for applications which repeated statements. The cache exists at the cursor level. If the application executes identical statements (presumably with different values) against the same cursor then this patch should eleminate the double network command penalty that oursql sees, and should see decreased CPU utilization because the server doesn't need to prepare the query again and the client doesn't need to escape values. That said, if the application recreates the cursor between queries or uses a large number of non-identical statements w/ small values then a mysql connector which uses the mysql_real_query interface (like MySQLdb) rather than mysql_stmt_* interface may be a better fit.

Essentially this patch saves the _statement objects into a fixed size LRU queue. If the query is identical, it will issue a free the results and reuse the statement. Because the statements are not immediately closed, result sets which have not been completly retrieved will remain allocated on the server side until the statement is reused or the statement falls off the end of the cache. In the case of large data sets this can be a substantial burden to the server. It is not enabled by default.

I'm still doing some testing for edge cases, but it seems to give a pretty substantial performance increase.

# Test table
CREATE TABLE `t1` (
  `id` int(11) NOT NULL
) ENGINE=BLACKHOLE DEFAULT CHARSET=latin1;

# oursql.wo.cache.py - Without Cache
import oursql
db = oursql.connect(host='localhost', user='root', db='test')
c = db.cursor()
for i in range(100000):
    c.execute('INSERT INTO `t1` VALUES (?)',(i,))

(venv)Codys-MacBook-Air-2:oursql-0.9.3.1 cody$ time python ~/Desktop/oursql.wo.cache.py

real 0m10.896s
user 0m1.915s
sys 0m3.542s

# oursql.w.cache.py - With statement cache
import oursql
db = oursql.connect(host='localhost', user='root', db='test')
c = db.cursor(statement_cache_size=5)
for i in range(100000):
    c.execute('INSERT INTO `t1` VALUES (?)',(i,))

(venv)Codys-MacBook-Air-2:oursql-0.9.3.1 cody$ time python ~/Desktop/oursql.w.cache.py

real 0m6.401s
user 0m1.438s
sys 0m1.952s