74 lines
3.6 KiB
Plaintext
74 lines
3.6 KiB
Plaintext
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= Re-select columns
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:toc:
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:toc-placement: macro
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:linkattrs:
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:icons: font
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:source-highlighter: highlight.js
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toc::[]
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[NOTE]
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====
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This post-processor is supported only for the SQL database connectors.
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====
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== Overview
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There are use cases where a {prodname} connector may not include a specific column's value in the change event, at not fault of its own but rather that's simply how the source database works.
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For example, TOAST columns in PostgreSQL, LOB columns in Oracle or Extended String columns with Oracle Exadata all come to mind.
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The `ReselectColumnsPostProcessor` provides a simple way to re-select one or more columns using an out-of-bands query to fetch the current column's state from the database table.
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The post processor can be configured to re-select columns that are `null`, columns that are emitted that use the configured `unavailable.value.placeholder` sentinel value.
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== Configuration example
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Configure a `PostProcessor` much in the same way that you would configure a `CustomConverter` or `Transformation`.
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To enable the connector to use the `ReselectColumnsPostProcessor`, add the following options to the connector configuration:
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[source,json]
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----
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"post-processors": "reselector", // <1>
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"reselector.type": "io.debezium.processors.reselect.ReselectColumnsPostProcessor", // <2>
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"reselector.reselect.columns.include.list": "<schema_name>.<table_name>:<colA>,<schema_name>.<table_name>:<colB>", // <3>
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"reselector.reselect.unavailable.values": "true", // <4>
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"reselector.reselect.null.values": "true" // <5>
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----
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<1> Comma-separated list of post-processor prefixes
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<2> The fully-qualified class type name for the post-processor
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<3> Comma-separated list of columns using the format `<schema>.<table>:<column>`
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<4> Enables or disables the re-selection of columns that contain the `unavailable.value.placeholder` sentinel value
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<5> Enables or disables the re-selection of columns that are `null`
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== Configuration options
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The following table lists the configuration options that you can set for the Reselect Columns post-processor.
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.Reselect columns post processor configuration options
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[cols="30%a,25%a,45%a"]
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|===
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|Property
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|Default
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|Description
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|[[reselect-columns-post-processor-property-reselect-columns-include-list]]<<reselect-columns-post-processor-property-reselect-columns-include-list, `+reselect.columns.include.list+`>>
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|No default
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|Comma-separated list of columns that should be re-selected from the source database, using the format `_<schema>_._<table>_:_<column>_` for each re-selectable column. +
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+
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This is mutually exclusive with `reselect.columns.exclude.list`.
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|[[reselect-columns-post-processor-property-reselect-columns-exclude-list]]<<reselect-columns-post-processor-property-reselect-columns-exclude-list, `+reselect.columns.exclude.list+`>>
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|No default
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|Comma-separated list of columns that should not be re-selected from the source database, using the format `_<schema>_._<table>_:_<column>_`. +
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+
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This is mutually exclusive with `reselect.columns.include.list`.
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|[[reselect-columns-post-processor-property-reselect-unavailable-values]]<<reselect-columns-post-processor-property-reselect-unavailable-values, `+reselect.unavailable.values+`>>
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|`true`
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|Specifies whether any column that matches the inclusion filter that has the value specified by the `unavailable.value.placeholder` connector configuration property will be re-selected.
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|[[reselect-columns-post-processor-property-reselect-null-values]]<<reselect-columns-post-processor-property-reselect-null-values, `+reselect.null.values+`>>
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|`true`
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|Specifies whether any column that matches the inclusion filter that has a `null` value will be re-selected.
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|===
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