Re: Unique index access path seems very slow

Hi Pap,

Honestly, there’s too many things here to follow. But your comparison of the sizes by counting characters in the sql*plus representation of the results is not right. Use the dump function on the results to see that the two different types have very different sizes. They represent exactly the same thing, but one is twice as efficient.

Thanks,
Andy

On Wed, Jan 25, 2023 at 10:28 AM, Pap <oracle.developer35_at_gmail.com> wrote:

> Thank You Andy and Mladen.
>
> I am little confused on the RAW VS HEX. As i see even i simply calculate
> the SHA512 value for a normal string as below, its still giving 128bytes as
> shown below without the hex function. So how the RAW value will help in
> minimizing the size of the column even we remove the RAWTOHEX conversion
> function here or I am missing anything here?
>
> Also as i tested , the conversion or the function(RAWTOHEX) call for
> ~3million rows itself is finishing in ~40 seconds in the inline view part,
> so as far as the RAWTOHEX function evaluation is concerned for this query,
> its a minimal percentage of the overall query execution time here.
>
> select (STANDARD_HASH (TO_CHAR (TRIM ( '225057')),'SHA512')) from dual
>
>
> 57AAF4B657557BAD68054B38C40149E2D8BD1EEB46A346DD6AC248228F55330B0832E8A1997855782811F0FA4C363FAB36597824157C3E10EAFFB0F07F61B666
>
> select (RAWTOHEX(STANDARD_HASH (TO_CHAR (TRIM ( '225057')),'SHA512')))
> from dual
>
>
> 57AAF4B657557BAD68054B38C40149E2D8BD1EEB46A346DD6AC248228F55330B0832E8A1997855782811F0FA4C363FAB36597824157C3E10EAFFB0F07F61B666
>
> I am struggling to understand below point. Do you mean to say adding
> 'order by COL1_SHA_512' to the inline view query itself? can you please
> explain a bit.
>
> " *I wonder if you were to place an extra order by subquery in there to
> join from. This might at least get you as good as you can get from the
> index."*
>
> I tried third suggestion of Jonathan, regarding turning off the bloom
> filter and not seeing much difference. Below is the sql monitor for both
> with and without bloom filter.
>
> https://gist.github.com/oracle9999/9b9a2d5da832e7b55cfa77abba8d0276
>
> The first two suggestion from Jonathan, are based on the design change of
> the transaction table tran_tab. And this table is having size ~25TB now and
> is having ~210 daily range partitions. As its being used across many
> applications queries , so would be difficult to go for this change. So we
> were looking if anything can be done by tweaking the design of this
> encrypted table TAB_ENCRYPT rather.
>
> We were thinking if its possible by someway, we can tie/generate certain
> number(say new sequence number) and maintain that additional column value
> for each of those encrypted value as reference, so that the length of this
> reference column will be minimal and index on this new column will be
> smaller too and also joining on that column will be efficient. Also this
> may not be easy as the same sequence number has to be referred and passed
> in all the up/downstream systems.
>
>
>
>
> On Wed, 25 Jan, 2023, 9:07 pm Andy Sayer, <andysayer_at_gmail.com> wrote:
>
>> I forgot about the impact of rawtohex, that would definitely give you a
>> lot of bang for your buck. It sounds to me like the impact of changing this
>> on your users is being exaggerated, you can easily make it presented in the
>> existing way if you needed to.
>>
>> Of course, if you do insist on keeping the full hex data stored, you can
>> use a function based index on hextoraw to create a smaller index.
>>
>> I don’t see what list partitioning is going to get you. You have
>> completely random data and you have no apparent way of doing anything about
>> that. Even if you were to eliminate it to just use one of those partitions
>> (which is 1/16^3 million chance) you’re still going to be reading the index
>> in a very random order.
>>
>> Saying this, I wonder if you were to place an extra order by subquery in
>> there to join from. This might at least get you as good as you can get from
>> the index.
>>
>> You should still go ahead with the smaller index. Partitioning is a no
>> from me.
>>
>> Thanks,
>> Andy
>>
>> On Wed, Jan 25, 2023 at 5:31 AM, Mladen Gogala <gogala.mladen_at_gmail.com>
>> wrote:
>>
>>> On 1/25/23 03:45, yudhi s wrote:
>>>
>>> Regarding your teams thought of list partition the encrypted table
>>> column with the last letter. You would end up in 16 list partitions.
>>> However as your data or say SHA512 value will be distributed across so you
>>> will end up relying only on luck to eliminate some table/index partition
>>> scans of your encrypted table, which I think would not be a good strategy.
>>>
>>> Pap, you should ask yourself one question only: do I feel lucky? Well,
>>> do you?
>>>
>>> --
>>> Mladen Gogala
>>> Database Consultant
>>> Tel: (347) 321-1217https://dbwhisperer.wordpress.com
>>>
>>>

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