php - Can someone explain Magentos Indexing feature in detail? -

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i kind of how indexing in magento works, haven't seen documentation on this. kind of know following.

  • how works
  • what purpose
  • why important
  • what details should know it
  • anything else can understand indexing , how used in magento

i think having information of great use others in boat don't indexing process.

update: after comment on question , ankur's answer, thinking missing in knowledge of normal database indexing. magento's version of handling indexing , better me answer in terms of database indexing in general, such link here how database indexing work?

magento's indexing similar database-level indexing in spirit. anton states, process of denormalization allow faster operation of site. let me try explain of thoughts behind magento database structure , why makes indexing necessary operate @ speed.

in more "typical" mysql database, table storing catalog products structured this:

product:     product_id int     sku        varchar     name       varchar     size       varchar     longdesc   varchar     shortdesc  varchar     ... etc ...

this fast retrieval, leaves fundamental problem piece of ecommerce software: do when want add more attributes? if sell toys, , rather size column, need age_range? well, add column, should clear in large store (think walmart, instance), result in rows 90% empty , attempting maintenance new attributes nigh impossible.

to combat problem, magento splits tables smaller units. don't want recreate entire eav system in answer, please accept simplified model:

product:     product_id int     sku        varchar  product_attribute_values     product_id   int     attribute_id int     value        misc  product_attributes     attribute_id     name

now it's possible add attributes @ entering new values product_attributes , putting adjoining records product_attribute_values. magento (with little more respect datatypes i've displayed here). in fact, there's no reason 2 products have identical fields @ all, can create entire product types different sets of attributes!

however, flexibility comes @ cost. if want find color of shirt in system (a trivial example), need find:

  1. the product_id of item (in product table)
  2. the attribute_id color (in attribute table)
  3. finally, actual value (in attribute_values table)

magento used work this, dead slow. so, allow better performance, made compromise: once shop owner has defined attributes want, go ahead , generate big table beginning. when changes, nuke space , generate on again. way, data stored in our nice flexible format, queried single table.

these resulting lookup tables magento "indexes". when re-index, blowing old table , generating again.

hope clarifies things bit!

thanks, joe


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