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admin:indexing:concepts:retrieval [2011/01/14 17:48]
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admin:indexing:concepts:retrieval [2016/06/28 22:38] (current)
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-{{page>:​top_add&​nofooter&​noeditbtn}}+~~NOTOC~~
  
-====== Administration:​ Indexing ​Strategies ​======+{{page>:​top_add&​nofooter&​noeditbtn}} 
 +====== Administration: ​Omnidex ​Indexing ======
  
 ===== Indexing Concepts ===== ===== Indexing Concepts =====
  
-**[[admin:​indexing:​concepts:​home|Overview]]** |  +[[admin:​indexing:​concepts:​home|Overview]] | 
-[[admin:​indexing:​concepts:​basics|Basics]] | +
 [[admin:​indexing:​concepts:​criteria|Criteria]] |  [[admin:​indexing:​concepts:​criteria|Criteria]] | 
 [[admin:​indexing:​concepts:​joins|Joins]] |  [[admin:​indexing:​concepts:​joins|Joins]] | 
 [[admin:​indexing:​concepts:​aggregations|Aggregations]] |  [[admin:​indexing:​concepts:​aggregations|Aggregations]] | 
 [[admin:​indexing:​concepts:​ordering|Ordering]] |  [[admin:​indexing:​concepts:​ordering|Ordering]] | 
-[[admin:​indexing:​concepts:​retrieval|Retrievals]] ​|  +**[[admin:​indexing:​concepts:​retrieval|Retrievals]]**
-[[admin:​indexing:​concepts:​alternatives|Alternatives]]+
  
 ---- ----
  
-==== Overview ​====+==== Retrievals ​====
  
-  * Basics of indexing +As Omnidex optimizes a query, it looks for ways to use indexes to process criteria, table joinsaggregations ​and ordering It may also find that the data to be returned to the user can be obtained ​from the indexes.  This can allow an entire query to be processed without ever accessing ​the database. ​ This technique provides exceptional performance.
-  * Indexing ​for criteria  +
-    * Basic cost of qualifications +
-    * Use of multiple ​indexes +
-    * MDK_RETRIEVAL_THRESHOLD (rename ​to QUALIFICATION_THRESHOLD) +
-  * Indexing for joins +
-    * Basic costs of joins +
-    * Prejoined indexes +
-    * Joining across databases +
-  * Indexing for aggregations +
-    * Basic cost of index scan +
-    * Use of partition qualifiers +
-    * ASK_RETRIEVAL_THRESHOLD (rename to AGGREGATION_THRESHOLD) +
-  * Indexing for ordering +
-    * Similar to aggregations +
-  * Indexing for retrieval +
-    * Obtaining ​data from indexes +
-    * Base cost of reading ​the index +
-  * Alternatives to indexing +
-    * Full table scans +
-    * Sort-merge +
-    * Hashed data caching+
  
 +The simplest example of this is queries that request counts. ​ Omnidex always maintains a count of the rows that have been qualified. ​ If the query requests a count, Omnidex can simply return it from the indexes. ​ Other queries may perform aggregations and use GROUP BY clauses. ​ These can be returned from the indexes as well.  ​
  
 +Other queries may request primary keys, or even data from other columns. ​ If these columns are found in the indexes, they will be returned from the index in order to minimize retrieval from the database. ​ Omnidex will automatically perform this optimization.
  
 +Using these techniques, it is possible to optimize complex queries without ever accessing the database. ​ A query may access dozens of tables, applying a wide variety of criteria and performing aggregations and ordering. ​ If Omnidex can, it will attempt to satisfy all of these aspects in the indexes, providing the best performance possible.
  
 =====  ===== =====  =====
  
-**[[admin:​indexing:​concepts:​criteria|Next]]**+**[[admin:​indexing:​concepts:​ordering|Prev]]** 
  
 ====== Additional Resources ====== ====== Additional Resources ======
 
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admin/indexing/concepts/retrieval.1295027287.txt.gz · Last modified: 2016/06/28 22:38 (external edit)