Unique index access path seems very slow
Date: Tue, 24 Jan 2023 00:16:04 +0530
Message-ID: <CAEjw_fg4AURJOGnCvnjgicYo9AKCVumsExhNzQXwVVKd90atNw_at_mail.gmail.com>
This database is on 19C of Oracle exadata. Below is the query and the sql monitor for both the FULL scan path and index access path. Also I had captured the non-zero stats from gv$sesstat for ~10minutes execution for each of those runs. The index access path has just processed ~82K in 30minutes using the index access path and has still not finished yet. We want to make this query finish in ~2-3minutes.
SELECT TRAN_TAB.COL1_SHA_512, TAB_ENCRYPT.TAB_ENCRYPT_COL2..... FROM (SELECT RAWTOHEX ( STANDARD_HASH (TO_CHAR (TRIM ( TRAN_TAB.LN4)),'SHA512')) AS COL1_SHA_512
FROM TRAN_TAB
WHERE TRAN_TAB.PD_CD(+) = 'XXX'
AND TRAN_TAB.PART_DT = to_date(:B1,'DD-MON-YYYY HH24:MI:SS')
AND TRAN_TAB.dt_cr between to_date(:B2,'DD-MON-YYYY HH24:MI:SS') and
to_date(:B3,'DD-MON-YYYY HH24:MI:SS')
) TRAN_TAB, TAB_ENCRYPT
WHERE TRAN_TAB.COL1_SHA_512 = TAB_ENCRYPT.COL1_SHA_512(+)
- "Full scan" path sql monitor + nonzero results from gv$sesstat from initial ~10minutes run*******
https://gist.github.com/oracle9999/b37160097fa8e3929fb66af61ebbf9ed
- "Index access" path sql monitor + nonzero results from gv$sesstat from initial ~10minutes run*******
https://gist.github.com/oracle9999/9792a70f748b71c365397c5458d3e9e8
The requirement is something as below...
We have two tables TRAN_TAB and TAB_ENCRYPT. Table(TAB_ENCRYPT) is an insert only table and holds the encrypted value(COL1_SHA_512) of a confidential column/attribute. Each row of the transaction table(TRAN_TAB) has to be checked/joined against all the encrypted column values of table TAB_ENCRYPT using the above query and the results along with additional columns from table tab_encrypt have to be sent to another downstream system. This query is supposed to run multiple times in a day so as to send the results to the downstream system as real time as possible based on the records in the transaction table tran_tab. Currently the plan is to run it once in ~5minutes. The table TAB_ENCRYPT holds ~3billion rows. And the transaction table TRAN_TAB will have Approx ~400 million rows per day/part_dt to get it joined with the encrypted column value- COL1_SHA_512.
As in the sql monitor, the original query was taking ~30minutes to join with ~3million rows in the transaction table. And the majority of the resources seems to be spent while full scanning the table TAB_ENCRYPT. And thus we tried creating a unique index on column "COL1_SHA_512" thinking it will be fast, but it appears to be further degrading the performance of this query. Want to understand why it's happening this way. Is it because the column holds ~128byte values so the index becomes too big to fit in cache? and then how can we fix this query?
The column "COL1_SHA_512" , holds the SHA512 encrypted value of another column. The sample encrypted values look something like below. The size of the index on this column is ~700GB. And the statistics of the index is as below. It contains all unique values though but i think because of its 128byte length the size of the index becomes this huge. The size of the table tran_tab is ~880GB.
"99983FB4F3BEAA516BE40B85706338B0D7E5D14D1B2A3C945D5F74947A3E8DA8E714D1761D008715CD46B6C6CDE8B99690F2AE04D97D9KHYU67GBF4589HNFRSDR"
*Column 'COL1_SHA_512' statistics:- *NUM_DISTINCT NULLABLE DENSITY
NUM_NULLS AVG_COL_LEN
2987284438 N 0.000000000334752187397831
0 129
*Unique Index(on column COL1_SHA_512) Statistics:- *INDEX_NAME
BLEVEL PCT_FREE LEAF_BLOCKS CLUSTERING_FACTOR NUM_ROWS TAB_ENCRYPT_UK 3 10 83389146 3008764650 3008764650
Regards
Pap
-- http://www.freelists.org/webpage/oracle-lReceived on Mon Jan 23 2023 - 19:46:04 CET