DBD::mysql (and soon DBD::drizzle) emulates prepared statements - it
catches the placeholders and does tricky replacements ;)
I like the idea of cached execution plans and result sets...
Monty Taylor wrote:
Ulf Wendel wrote:
Monty Taylor schrieb:
Ulf Wendel wrote:
Brian tried to kick off some brainstorming on PS in his blog [1]. Both
he and Lukas Smith [2], as of shortly a [Co-]Release Manager of the PHP
5.3 series, have blogged about PS before I found time to raise my voice
on PDO and PS [3]. Its been a rather vivid blog discussion.
Things I remember from the discussion:
- current PS implementation of the server does not scale well
And never will.
- todays developers are lazy and maybe less skilled:
they rely on garbage collections and keep handles open
for ages - the server
- the server does not do much more than cache the parse tree:
parsing can make 25% of the run-time of a short query
Well, the parsing problem is actually a whole other conversation I'm
trying to have... (in short, I want to push parsing to the client
library and have the ability to send the parse-tree over the wire)
There is more behind than just parsing.
The concept of Prepared Statements came up at a time when I was still in
the Kindergarten or maybe not even planned to be ever born. From what I
know, PS are designed for classical host applications. The setup
consists of a single central database server and limited number of a few
hundred workstations. The workstations run the same program all day.
Probably even with less dynamic SQL. Its been the times of embedded SQL.
A perfect world for caching as much as you can on the server:
- parse-trees
- execution plans
- DB internal file system handles
- ... - whatever resource you can "cache" or "reserve"
Clients change only once per day, many recurring queries with just a
little bit different parameters etc.
Typical web applications should be characterized by a far higher number
of clients. And the more clients, the more challenging it is to scale on
a central element. I get that.
But can we move all of the theoretical benefits of server-side PS
towards the client? I see that a client can parse SQL and do parameter
substituition. But what about:
- execution plans
- DB internal file system handles
- ... - whatever resource you can "cache" or "reserve"
- binary protocol can mean significantly less conversions
- binary protocol can mean less traffic
What is the Drizzle roadmap on Prepared Statements given that PHP, a
major player in the web market, will not play nicely with Drizzle
without a vision implemented by Drizzle and MySQL Connector team folks?
If you want to scale in a massive web scale out environment, Server-Side
prepared statements are a terrible idea. Full stop. Same thing with
So, the Drizzle idea is on client-side PS. But how do they work? What
about parser updates? Will Drizzle make the SQL parser a plugin that
clients can use as well?
I would _like_ to. I'm not sure if I've got everyone else on board with
that though.
Whether the server-side has PS or not or they are any good or not, I
can't believe PHP can't provide a good emulation layer for their users
That's not at the hearth of my question. It may be possible to develop a
solid client-side PS emulation for PHP. But it will take time and
resources. As long as its not available you will hear the PHP folks, the
self-declared target audience for Drizzle, bail at you.
Gotcha... with you now...
So... what if we faked prepared statements in the client lib just like
java and the like are already doing for us? Have:
drizzle_stmt_init() return a DRIZZLE_STMT struct, have the DRIZZLE_BIND
do its thing, but then actually do the same type of faking there that
java and them do? Would that be useful?
The question is on the how to do it, assuming that we really think that
preparing (= caching) statements makes sense at all.
Well, I think preparing statements and binding variables to them is a
good programming practice...
Monty
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