As data changes, the transformed data must be updated to the frontend of the website / store / storeview - this is done through indexing. The relationship between the data in the backend and the data in the frontend: the data in the backend is non-indexed and completely up-to-date vs. the data on the frontend which is indexed.
Data in Magento (catalog, customer, attributes, etc) is organised across many database tables. In order for site performance to be optimised, Magento accumulates data in special tables using indexers. For a fully merchandised website, you can imagine the amount of data and data changes that must be managed in Magento on a consistent basis - if indexing did not exist, Magento would have to search for and calculate all the data on the spot - leading for much slower load times etc.
While there are many different types of indexes for all the various types of data that need to be indexed in Magento (which can be viewed via the System > Configuration > Index Management screen), examples include:
- Category products: Creates category/product associations
- Product price: Pre-calculates product prices
- Product entity attribute value: Reorganises the EAV product structure to flat structure
The way the reindex is performed, depends on what the mode of the index is. modes available are:
- Manual Update
- Update on Save
- Update on Schedule (Enterprise only)
Note: Since performing a reindex can have a negligible effect on site performance, it is always recommended that indexes are scheduled in where possible (as as to be run on off-peak hours).
The mode of the index can be changed by navigating to the Index Management screen (via System > Configuration), ticking the required indexes and then selecting 'Change Index Mode' from the Actions dropdown. Once selected, click the Submit button.
Performing a Re-index
As re-indexing can have a negative affect on store performance, it is again always recommended that re-indexes are scheduled in where possible or performed at off peak times.
1. Navigate to the System > Configuration > Index Management screen.
2. Select all the indexes you would like to reindex (or use the Select All to select all)
3. From the Actions dropdown, select 'Reindex data' and then click the Submit button.
Note: Any questions in regards to when why and how to perform a re-index, please get in touch and we can take into consideration how they are best organised based on considerations like the size of your catalog etc.