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List_contains

As explained in DuckDB in Action

list_contains is a DuckDB function that tests whether a list contains a specified value.

list_contains tests whether a list contains a specified value. In a posts table, it replaces substring matching when tags are stored as a list, making membership explicit and usable in SQL filters. section 10.1.7

Count posts carrying a tag

SELECT count(*) FROM posts WHERE postTypeId = 1 AND list_contains(tagNames, 'java'); The same predicate works with an enum list: list_contains(tagEnums, 'java'). On 28 million rows, the string-list operation runs in 0.24 seconds; the enum-list version runs in 0.17 seconds. section 10.1.7

How DuckDB in Action covers it

How deep it goes
Defines membership filtering and compares string-list and enum-list runtimes, without detailing function internals.
Examples
Demonstrates counting Java-tagged posts using VARCHAR[] and ENUM[] columns.
What it assumes
Assumes SQL filtering and list-valued columns, while the examples establish tag-list preparation and enum conversion.
What you can do after
Apply it via DuckDB SQL to filter list-valued rows and compare string-list and enum-list representations.
How it connects
Connects list_contains with LIST, ENUM, list_transform, and SQL filtering.
Cover of DuckDB in Action
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This explainer was generated by Manning's knowledge graph from the text of DuckDB in Action. The section links point to the parts of the book it draws on.