On Sun, 13 Nov 2005, Joost Kraaijeveld wrote:
I have a connection that is created with "prepareThreshold=1" in the
connection string. I use a prepared statement that I fill with
addbatch() and that I execute with executeBatch() (for full source: see
"application.java" attachment).
LOG: statement: PREPARE S_2 AS update prototype.customers set title=
$1 , defaultcurrency=$2, defaulttermsofdelivery=$3 ,
defaulttermsofpayment=$4 where customernumber=$5
LOG: statement: <BIND>
LOG: statement: EXECUTE <unnamed> [PREPARE: update
prototype.customers set title=$1 , defaultcurrency=$2, defaultter
msofdelivery=$3, defaulttermsofpayment=$4 where customernumber=$5]
LOG: duration: 773.841 ms
LOG: statement: <BIND>
LOG: statement: EXECUTE <unnamed> [PREPARE: update
prototype.customers set title=$1 , defaultcurrency=$2, defaultter
msofdelivery=$3, defaulttermsofpayment=$4 where customernumber=$5]
LOG: duration: 377.981 ms
Does this output mean that the prepared statement with the name "S_2" is
not used in the following 2 EXECUTE statements and that therefor each
execute statement is planned again?
The driver does not actually issue PREPARE or EXECUTE statements; the
server is pretending that the protocol-level Prepare/Bind/Execute
messages are actually something issuing PREPARE/EXECUTE at the SQL level
(but in reality, nothing is issuing precisely the queries that are being
logged -- the query that is submitted is just your plain "update ..."
query).
The PREPARE S_2 AS .. logs that a Prepare message was processed (for the
query "update ..."). This does parsing/planning work and creates a named
prepared statement called S_2 on the server.
The <BIND> means that some previously prepared statement (you can't tell
which statement from what is logged! -- but it's S_2 in this case) is
being bound to parameter values via a Bind message, creating an unnamed
portal.
The EXECUTE <unnamed> means the unnamed portal is being executed via an
Execute message. It also logs the underlying statement at that point,
but not the statement name (!).
So if I read the logs right, the single prepared statement S_2 *is*
being reused in the case above.
Yes, it's a horribly confusing way for the server to log things. I
raised it on -hackers earlier in the 8.1 cycle, but I've not had time to
work on it myself.
-O
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