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Query extension metadata using the standard SQL interfaces below.

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System Views

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INFORMATION_SCHEMA.EXTENSIONS

Lists all installed extensions. Schema: 
SELECT
    EXTENSION_NAME,
    EXTENSION_VERSION
FROM INFORMATION_SCHEMA.EXTENSIONS;
Example: 
-- List all installed extensions
SELECT * FROM INFORMATION_SCHEMA.EXTENSIONS;

-- Check specific extension version
SELECT EXTENSION_VERSION
FROM INFORMATION_SCHEMA.EXTENSIONS
WHERE EXTENSION_NAME = 'vsql_complex';
Sample Output: 
+------------------+-------------------+
| EXTENSION_NAME   | EXTENSION_VERSION |
+------------------+-------------------+
| vsql_complex     | 0.0.1             |
| vsql_uuid        | 0.2.1             |
+------------------+-------------------+

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INFORMATION_SCHEMA.COLUMNS (Custom Types)

Columns using custom extension types are visible through the standard INFORMATION_SCHEMA.COLUMNS view. Custom types appear as extension_name.type_name in the DATA_TYPE and COLUMN_TYPE columns (e.g., vsql_complex.COMPLEX). Example: 
-- Find all columns using custom extension types
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE DATA_TYPE LIKE '%.%'
ORDER BY TABLE_SCHEMA, TABLE_NAME;

-- Find columns using a specific extension's types
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE DATA_TYPE LIKE 'vsql_complex.%';
Sample Output: 
+--------------+------------+-------------+---------------------+
| TABLE_SCHEMA | TABLE_NAME | COLUMN_NAME | DATA_TYPE           |
+--------------+------------+-------------+---------------------+
| mydb         | signals    | impedance   | vsql_complex.COMPLEX|
| mydb         | signals    | frequency   | vsql_complex.COMPLEX|
+--------------+------------+-------------+---------------------+

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Common Queries

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Find Extension Dependencies

Find which columns use a specific extension’s types before uninstalling: 
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE DATA_TYPE LIKE 'vsql_complex.%';

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List All Extensions and Their Custom Type Columns

-- All installed extensions
SELECT EXTENSION_NAME, EXTENSION_VERSION
FROM INFORMATION_SCHEMA.EXTENSIONS
ORDER BY EXTENSION_NAME;

-- All columns using custom types across all extensions
SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE DATA_TYPE LIKE '%.%'
ORDER BY DATA_TYPE, TABLE_SCHEMA, TABLE_NAME;

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Find Tables Using Extension Types

SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE DATA_TYPE LIKE 'vsql_complex.%'
ORDER BY TABLE_SCHEMA, TABLE_NAME;

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Next Steps

Managing Extensions

Monitor and troubleshoot extensions

Install Extensions

Add new extensions

Extension Architecture

Understand the internals

Available Extensions

Browse extension catalog