Using a case study to thoroughly understand 10046trace-byte-level in-depth cracking

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PM, 10046-byte-level in-depth cracking

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SQL optimization course series I CBO internal Algorithms

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I only asked one question. Can someone really figure out the> choice rate? DIS is not clear.

++ Let me show you something

--------------------------------------------------------------------------| Id  | Operation  | Name | Rows  | Bytes | Cost (%CPU)| Time |--------------------------------------------------------------------------|   0 | SELECT STATEMENT  | |     1 |    10 |   349   (1)| 00:00:05 ||*  1 |  TABLE ACCESS FULL| T1 |     1 |    10 |   349   (1)| 00:00:05 |--------------------------------------------------------------------------Predicate Information (identified by operation id):---------------------------------------------------   1 - filter("OBJECT_NAME"='00440')table name:T1column name:OBJECT_NAMEnum_rows:87417num distinct:48128num_nulls:797density:.0000115446779034865histogram:HEIGHT BALANCEDhigh_value:4435(D5) -- internal value:354151154089362000000000000000000000low_value:3030343432(00442) -- internal value:25020794088876500000000000000000000000400 internal Value : 250207940886347000000000000000000000ENDPOINT_VALUE     ENDPOINT_NUMBER BUCKET_COUNT-------------------- --------------- ------------46641  40147796  411A1  498B2  589C3  668D5  759

Density = (Bucket_total-Buckets_all_popular_value )/

Sel =. 00001136*(87417-797)/87417*(1-(250207940888765000000000000000000000-250207940886347000000000000000000000)/(354151154089362000000000000000000000-250207940888765000000000000000000000 )))

This is: col = val and val 2 * low_value-high_value

High_value: 4435 (D5) -- internal value: 354151154089362000000000000000000000

00400 internal Value: 250207940886347000000000000000000000

How are these three numbers obtained?

D5 is saved in dba_tab_columns as follows: 4435. In fact, the internal oracle computing value is 354151154089362000000000000000000000.

As a matter of fact, he is telling you how to COST. Instead, he wants to tell you how to study oracle algorithms.

It is actually telling you how to guess. It is also wrong.

For example, cardinality uses ceil (). In fact, oracle uses round in most cases.

Are you helpless in the face of slow production SQL statements? I am just an example here...

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Choice rate, base calculation formula

1. Important Concepts

Join

5. Hash Join and Sort Merge Join

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