Re: Problem with PgTcl auditing function on trigger

>
>
> ----- Original Message ----
> From: Glyn Astill <glynastill(at)yahoo(dot)co(dot)uk>
> To: pgsql-hackers(at)postgresql(dot)org
> Sent: Friday, January 4, 2008 5:23:18 AM
> Subject: [HACKERS] Problem with PgTcl auditing function on trigger
>
> Hi people,
>
> I've tried posting on the general list about this, but I never get
> a
> reply, so I'm trying here.
>
> I have a function that is run each time an INSERT, DELETE or UPDATE
> happens on a row and log into an audit table.
>
> It is based on the info here:
>
> http://www.alberton.info/postgresql_table_audit.html
>
> We have a table Customers.CREDIT with a primary key "NUMBER",
> "TRANSNO", "RECNUM".
>
> I have a trigger as follows:
>
> CREATE TRIGGER "tg_audit_credit"
> AFTER INSERT OR DELETE OR UPDATE ON "Customers"."CREDIT"
> FOR EACH ROW
> EXECUTE PROCEDURE "log_to_audit_table" ();
>
> This uses the attached tcl function which basically runs this for a
> delete
>
> spi_exec -array C "INSERT INTO audit_table(ts, usr, tbl, fld,
> pk_name, pk_value, mod_type, old_val, new_val)
> VALUES (CURRENT_TIMESTAMP, '$tguser', '$tgname',
> '$modified_field',
> '$pk_name', '$pk_value', '$TG_op', '$previous_value', NULL)"
>
> The function works fine for this SQL statement
>
> delete from "CREDIT" where "TRANSNO" < 11148188 AND "TRANSNO" >
> 11148180;
>
> However if I try this one I get a syntax error.
>
> delete from "CREDIT" where "RECNUM" < 2484907 AND "RECNUM" >
> 2484905;
>

Is the Tcl function the same for RECNUM and TRANSNO? I noticed you have
set pk_name "RECNUM" ...

Not sure if you are changing this when you run the different DELETEs.

>
> The error is below. Do I need to escape my strings? And if so how
> do
> I do this?
>
> Thanks
> Glyn
>
>
> SEE=# delete from "CREDIT" where "RECNUM" < 2484907 AND "RECNUM" >
> 2484905;
> ERROR: syntax error at or near "S"
> CONTEXT: syntax error at or near "S"
> while executing
> "spi_exec -array C "INSERT INTO audit_table(ts, usr, tbl, fld,
> pk_name, pk_value, mod_type, old_val, new_val)
> VALUES (CURRENT_TIMESTAMP, '$tguser', '$t..."
> ("foreach" body line 5)
> invoked from within
> "foreach field $TG_relatts {
> if {! [string equal -nocase [lindex [array get OLD $field] 0]
> $pk_name]} {
> set modified_field [lindex [array get..."
> ("DELETE" arm line 11)
> invoked from within
> "switch $TG_op {
> INSERT {
>
> #get PK value
> foreach field $TG_relatts {
> if {[string equal -nocase [lindex [array get NEW $field] 0]
> $pk_name]} {..."
> (procedure "__PLTcl_proc_5667381_trigger_16644" line 23)
> invoked from within
> "__PLTcl_proc_5667381_trigger_16644 tg_audit_credit 16644 CREDIT
> Customers {{} RECNUM TRANSNO NUMBER EXMON EXYEAR OLDTICK COACHES
> VALUE POSTAGE DEPOSIT..."
>

I'm not sure where the error is coming from, off hand. The only thing
I can think of now is that you may need to [quote] the values or
use spi_execp instead. Perhaps there is a ' in there somewhere causing problems.

As a side note, just some tips (i realize that you got this from the link above):

You have several instances of constructs such as:

if {! [string equal -nocase [lindex [array get NEW $field] 0] $pk_name]} {

but this really is just $field...so you don't need all of that. You can just do:

if {! [string equal -nocase $field $pk_name]} {

Similiarily, you have this construct
set pk_value [lindex [array get NEW $field] 1]

But you can use this instead:
set pk_value $NEW($field)

And then, this whole block:

foreach field $TG_relatts {
if {[string equal -nocase [lindex [array get NEW $field] 0] $pk_name]} {
set pk_value [lindex [array get NEW $field] 1]
break;
}
}

Not sure the purpose here, but you should be able to just do:

if {[info exists NEW($pk_name)]} {
set pk_value $NEW($pk_name)
} else {
# something went wrong here...need this if there's a chance $pk_name might not be there
}

Note also that TG_relatts has an empty element as the first element of the list, so this
if {! [string equal -nocase [lindex [array get OLD $field] 0] $pk_name]} {

may be giving you trouble, since it won't catch the empty element.

so, you could write that particular loop construct as such:
foreach field [lrange $TG_relatts 1 end] {
if {! [string equal -nocase $field $pk_name]} {
set modified_field $field
set previous_value $OLD($field)
spi_exec -array C "INSERT INTO audit_table(ts, usr, tbl, fld, pk_name, pk_value, mod_type, old_val, new_val)
VALUES (CURRENT_TIMESTAMP, '$tguser', '$tgname', '$modified_field', '$pk_name', '$pk_value', '$TG_op', '$previous_value', NULL)"
}
}

You may to throw some [elog]'s in there, to see what's going on as well.

HTH,
--brett

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