Chapter 61. Writing a Custom Scan Provider

Chapter 61. Writing a Custom Scan Provider
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Table of Contents

61.1.1. Custom Scan Path Callbacks

61.2.1. Custom Scan Plan Callbacks

61.3.1. Custom Scan Execution Callbacks

+ PostgreSQL supports a set of experimental facilities which + are intended to allow extension modules to add new scan types to the system. + Unlike a foreign data wrapper, which is only + responsible for knowing how to scan its own foreign tables, a custom scan + provider can provide an alternative method of scanning any relation in the + system. Typically, the motivation for writing a custom scan provider will + be to allow the use of some optimization not supported by the core + system, such as caching or some form of hardware acceleration. This chapter + outlines how to write a new custom scan provider. +

+ Implementing a new type of custom scan is a three-step process. First, + during planning, it is necessary to generate access paths representing a + scan using the proposed strategy. Second, if one of those access paths + is selected by the planner as the optimal strategy for scanning a + particular relation, the access path must be converted to a plan. + Finally, it must be possible to execute the plan and generate the same + results that would have been generated for any other access path targeting + the same relation. +

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60.1. Sampling Method Support Functions	Home	61.1. Creating Custom Scan Paths