Oracle Database - The Query Plan Estimator

Card Puncher Data Processing

About

Query Optimizer Process

The estimator is involved in the query optimizer process. Its main task is to measure the plans that give the plan generator.

It generates three different types of measures :

These measures are related to each other, and one is derived from another.

The end goal of the estimator is to estimate the overall cost of a given plan. If statistics are available, then the estimator uses them to compute the measures. The statistics improve the degree of accuracy of the measures.




Discover More
Card Puncher Data Processing
Glossary

(CREATE, ALTER, DROP) (GRANT, REVOKE) (SELECT, UPDATE, INSERT, DELETE) (COMMIT, ROLLBACK) NLS (National Language Support) UDML is the abbreviation for Universal Database Markup Language ...
Obiee Fragmentation Content One Column
OBIEE - Fragmentation Content, value-based, horizontal partitioning

This capabilities of OBIEE is also known as : Content Fragmentation Value-Based fragmentation Fact Horizontal Partitioning The term Fragmentation is more an OBIEE term whereas the term partitioning...
Sql Developer Autotrace
Oracle Database - Autotrace

Autotrace is: a system variable of sql plus can also be found in SQL Developer AUTOTRACE provides you: an execution plan (such as explain plan) and some important regarding its actual execution....
Card Puncher Data Processing
Oracle Database - Rows (of Card as Cardinality for 9i)

Cardinality is the second measure that Query Plan Estimator use to estimate a execution plan. It represents the number of rows in a row set that the Optimizer expects to come back. Here, the row set...
Card Puncher Data Processing
Oracle Database - Selectivity

The first measure of the plan_estimator, selectivity, represents a fraction of rows from a row set. The row set can be a base table, a view, or the result of a join or a GROUP BY operator. The selectivity...
Histogram Height Balanced Uniform Distribution
Oracle Database - Statistics - Histogram (Column statistics)

Data Dictionary Column statistics may be stored as histograms. These histograms provide accurate estimates of the distribution of column data. Histograms provide improved selectivity estimates in the presence...
Card Puncher Data Processing
Oracle Database - The Query Plan Generator

The main function of the plan generator is to try out different possible plans for a given query and pick the one that has the lowest . The plan for a query is established by first generating subplans...
Oracle Database Sql Processing
SQL Engine - Optimizer Statistics

In order to make the best execution plan, the optimizer uses statistics on the database objects and the computer system. data dictionary Optimizer statistics are always treated as estimates and can become...
Oracle Database Sql Processing
SQL Engine - (Query Plan) Cost

in relational operation. The cost is an estimated value proportional to the expected resource use needed to execute the statement with a particular execution_plan. The plan estimator calculates the cost...
Query Optimizer Process
SQL Engine - Query Optimizer (Query Optimization)

in a SQL Engine. A SQL statement can be executed in many different ways, such as: full table scans, index scans, nested loops, hash joins. The query optimizer determines the most efficient...



Share this page:
Follow us:
Task Runner