Posted by frizzle on 12/17/02 11:53

Andy Hassall wrote:
> On 20 Jul 2006 14:36:19 -0700, "frizzle" <phpfrizzle@gmail.com> wrote:
>
> >>> I assume the result to be equal.
> >>> Would mysql_insert_id() still require a DB connection to be open?
> >>
> >> Yes, it's a MySQL call.
> >
> >So you'd have to run another extra call to the database, instead of
> >getting it from cache ?
> >Wouldn't that make it slower?
> >Not quite getting this, but liked to know how it works ...
>
> Interesting question, as the docs don't seem to explicitly state whether it
> does or does not.
>
> Tracing network traffic with Ethereal, MySQL client 5.0.22, server version
> 4.1.7 on another machine, and sleep() calls between each step to make it
> obvious what is happening at each stage, shows that calling mysql_insert_id()
> does not result in any communication with the server; so the value must be sent
> across and stored in the client as part of running the previous mysql_query().
>
> Looking at the individual packets, this is indeed the case; the ID is returned
> as part of the payload in the "OK" packet in reply to the query:
>
>
> No. Time Source Destination Protocol Info
> 12 0.006948 192.168.1.101 192.168.1.100 MySQL Request
> Command: Query : insert into t (id) values (null)
>
> Frame 12 (91 bytes on wire, 91 bytes captured)
> Ethernet II, Src: SC&C_d5:81:1c (00:00:21:d5:81:1c), Dst: SC&C_d5:81:1a
> (00:00:21:d5:81:1a)
> Internet Protocol, Src: 192.168.1.101 (192.168.1.101), Dst: 192.168.1.100
> (192.168.1.100)
> Transmission Control Protocol, Src Port: 3693 (3693), Dst Port: 3306 (3306),
> Seq: 86, Ack: 83, Len: 37
> MySQL Protocol
> Packet Length: 33
> Packet Number: 0
> Command
> Command: Query (3)
> Parameter: insert into t (id) values (null)
>
> No. Time Source Destination Protocol Info
> 13 0.008511 192.168.1.100 192.168.1.101 MySQL Response
> OK
>
> Frame 13 (65 bytes on wire, 65 bytes captured)
> Ethernet II, Src: SC&C_d5:81:1a (00:00:21:d5:81:1a), Dst: SC&C_d5:81:1c
> (00:00:21:d5:81:1c)
> Internet Protocol, Src: 192.168.1.100 (192.168.1.100), Dst: 192.168.1.101
> (192.168.1.101)
> Transmission Control Protocol, Src Port: 3306 (3306), Dst Port: 3693 (3693),
> Seq: 83, Ack: 123, Len: 11
> MySQL Protocol
> Packet Length: 7
> Packet Number: 1
> Response Code: 0
> Payload: \001\017\002
>
>
> In this case the ID was 15 - which is octal \017 - the middle byte in the
> payload of the response to the query.
>
> --
> Andy Hassall :: andy@andyh.co.uk :: http://www.andyh.co.uk
> http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool

Wow! Thanks for the extensive information. I understand your
conclusion, but the rest is unfortunately just a load of jibberish (to
technical) to me ... :(

Frizzle.

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