PostgreSQL查看索引是否失效

在PostgreSQL中，您可以通过查询pg_index和pg_attribute视图来检查索引是否失效。以下是一个SQL查询示例，它检查所有索引并确定哪些索引不可用或可能已经失效：

SELECT
    n.nspname as "Schema",
    t.relname as "Table",
    i.relname as "Index",
    CASE
        WHEN NOT i.indisvalid THEN 'Invalid'
        WHEN NOT i.indisready THEN 'Not Ready'
        ELSE 'Valid'
    END as "Status"
FROM
    pg_class t,
    pg_namespace n,
    pg_index i
WHERE
    t.relnamespace = n.oid
    AND t.oid = i.indrelid
    AND t.relkind = 'r'  -- only tables
    AND i.indisprimary = false  -- exclude primary keys
    AND i.indisvalid = false  -- only invalid indexes
UNION ALL
SELECT
    n.nspname as "Schema",
    t.relname as "Table",
    NULL as "Index",
    'No Index' as "Status"
FROM
    pg_class t,
    pg_namespace n
WHERE
    t.relnamespace = n.oid
    AND t.relkind = 'r'  -- only tables
    AND NOT EXISTS (
        SELECT 1
        FROM pg_index i
        WHERE i.indrelid = t.oid AND i.indisprimary = false
    )  -- no other indexes
ORDER BY
    "Schema",
    "Table",
    "Index" IS NOT NULL DESC;

这个查询将列出所有无效的索引以及没有索引的表。如果您想要检查特定的索引，可以在WHERE子句中添加更多的条件来指定表名和索引名。