如何识别 PostgreSQL 索引中包含的列？

识别 PostgreSQL 中索引的列

在 PostgreSQL 中，可以使用系统表来获取参与索引的列。请按照以下步骤操作：

SELECT
    t.relname AS table_name,  -- Name of the indexed table
    i.relname AS index_name,  -- Name of the index
    a.attname AS column_name  -- Indexed column name
FROM
    pg_class t  -- Catalog table for tables
JOIN
    pg_class i ON t.oid = i.indrelid  -- Catalog table for indexes
JOIN
    pg_index ix ON i.oid = ix.indexrelid  -- Index information
JOIN
    pg_attribute a ON t.oid = a.attrelid AND a.attnum = ANY(ix.indkey)  -- Join with table attributes
WHERE
    t.relkind = 'r'  -- Restrict to regular tables
    AND t.relname LIKE 'test%';  -- Filter based on pattern (optional)
ORDER BY
    t.relname,  -- Sort by table name
    i.relname;   -- Then sort by index name

示例输出：

table_name | index_name | column_name
------------+------------+-------------
test       | pk_test    | a
test       | pk_test    | b
test2      | uk_test2   | b
test2      | uk_test2   | c
test3      | uk_test3ab | a
test3      | uk_test3ab | b
test3      | uk_test3b  | b
test3      | uk_test3c  | c

为了进一步分析，您可以对列名称进行分组并汇总结果：

SELECT
    t.relname AS table_name,  -- Name of the indexed table
    i.relname AS index_name,  -- Name of the index
    array_to_string(array_agg(a.attname), ', ') AS column_names  -- Concatenate column names
FROM
    pg_class t  -- Catalog table for tables
JOIN
    pg_class i ON t.oid = i.indrelid  -- Catalog table for indexes
JOIN
    pg_index ix ON i.oid = ix.indexrelid  -- Index information
JOIN
    pg_attribute a ON t.oid = a.attrelid AND a.attnum = ANY(ix.indkey)  -- Join with table attributes
WHERE
    t.relkind = 'r'  -- Restrict to regular tables
    AND t.relname LIKE 'test%';  -- Filter based on pattern (optional)
GROUP BY
    t.relname,  -- Group by table name
    i.relname  -- Then group by index name
ORDER BY
    t.relname,  -- Sort by table name
    i.relname;   -- Then sort by index name

示例输出：

table_name | index_name | column_names
------------+------------+--------------
test       | pk_test    | a, b
test2      | uk_test2   | b, c
test3      | uk_test3ab | a, b
test3      | uk_test3b  | b
test3      | uk_test3c  | c

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