Firebird creates indexes to enforce various integrity constraints automatically. To delete these indexes, it is necessary to drop the constraints that use them.
Use of the constraint indexes is not limited to their work supporting the integrity of keys and relationships. They are considered, along with all others, when queries are prepared.
When defining your own indexes, it is of utmost importance to avoid creating any index that duplicates an automatically generated one. It puts the optimizer (see the upcoming section “Query Plans”) in the unhappy position of having to choose between equals. In many cases, it will solve the problem by not choosing either of them.
Importing Legacy Indexes
Do not import “primary indexes” with tables from a migrating DBMS. There are two important reasons to abandon these indexes:
The sort direction of indexes in Firebird is important. It is a mistake to assume that the same index can be used to sort or search “both ways”—that, is lowest-to-highest and highest-to-lowest. As a rule of thumb, ASC (ascending) indexes will help searches where relatively low values are sought, whereas DESC (descending) indexes will help for maximum or high values.
If an automatic index is ASC (the default), there will be no problems if you need to define a DESC index using the same column(s). The reverse is also true: From v.1.5 onward, you can choose to have the automatic indexes for keys created in descending order. The optimizer will not be upset if you also create an ascending one on the same columns.
Firebird Related Interview Questions
|RDBMS Interview Questions||MySQL Interview Questions|
|Linux Interview Questions||Mac OS X Deployment Interview Questions|
|Windows Administration Interview Questions||Windows Server 2003 Interview Questions|
|SQL Interview Questions||NoSQL Interview Questions|
|Advanced C++ Interview Questions|
Introduction To Client/server Architecture
About Firebird Data Types
Date And Time Types
Blobs And Arrays
From Drawing Board To Database
Creating And Maintaining A Database
Firebird’s Sql Language
Expressions And Predicates
Querying Multiple Tables
Ordered And Aggregated Sets
Overview Of Firebird Transactions In
Programming With Transactions
Introduction To Firebird Programming
Developing Psql Modules
Error Handling And Events
Security In The Operating Environment
Configuration And Special Features
Interactive Sql Utility (isql)
Database Backup And Restore (gbak)
Housekeeping Tool (gfix)
Understanding The Lock Manager
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