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Design Decisions

In This Chapter

Storing Data in Shared Memory

Functions That Allocate and Free Memory

Memory-Duration Options

Persistent User Data

Accessing Database and System Catalog Tables

Executing a UDR Across Databases of the Same Database Server Instance

Handling the Unexpected

Using Callback Functions

Using Error Messages

Supporting Data Definition Statements

Interpreting the Table Descriptor

Managing Storage Spaces

Choosing DataBlade API Functions

Setting the am_sptype Value

Creating a Default Storage Space

Ensuring Data Integrity

Checking Storage-Space Type

Supporting Fragmentation

Providing Configuration Keywords

Leveraging Indexes on Virtual Tables

Processing Queries

Interpreting the Scan Descriptor

Interpreting the Qualification Descriptor

Simple Functions

Runtime Values as Arguments

Complex Boolean Expressions

Qualifying Data

Qualification by the Database Server

Qualification by the Access Method

Qualification by External Software

Supporting Query Plan Evaluation

Enhancing Performance

Executing in Parallel

Buffering Multiple Results

Supporting Data Retrieval, Manipulation, and Return

Checking Isolation Levels

Converting to and from Row Format

Determining Transaction Success or Failure

Supplying Error Messages and a User Guide

Avoiding Database Server Exceptions

Statements That the Access Method Does Not Support

Keywords That the Access Method Does Not Support

Storage Spaces and Fragmentation

Features That the VTI Does Not Support

Notifying the User About Access-Method Constraints

Documenting Nonstandard Features

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