Re: [HACKERS] LZTEXT for rule plan stings

Don Baccus <dhogaza(at)pacifier(dot)com> writes:
>> What's your basis for asserting the rule is only ~ 1K?

> I looked at the string dumped by pg_dump and it didn't appear to be
> anywhere near 8KB, so I presumed that the actual data stuffed into
> the rule is larger than whatever gets dumped out as the source
> representation.

Yes, the source representation is *vastly* more compact. A single
result column might look like "tab1.product_id" when dumped by pg_dump,
but the nodetree dump looks more like

{ TARGETENTRY
:resdom
{ RESDOM
:resno 1
:restype 23
:restypmod -1
:resname product_id
:reskey 0
:reskeyop 0
:ressortgroupref 0
:resjunk false
}

:expr
{ VAR
:varno 1
:varattno 1
:vartype 23
:vartypmod -1
:varlevelsup 0
:varnoold 1
:varoattno 1
}
}

and (except for not using any excess whitespace) that is exactly what
goes into a rule action string.

As you can see, this is very amenable to compression, especially
when you have a lot of columns in a view.

Someday we might think about using a more compact representation for
stored rules, but there are advantages to using a format that's fairly
easy for a human to examine.

regards, tom lane