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索引膨胀的几个来源：1 大量删除发生后，导致索引页面稀疏，降低了索引使用效率。2 PostgresQL 9.0之前的版本，vacuum full 会同样导致索引页面稀疏。3  长时间运行的事务，禁止vacuum对表的清理工作，因而导致页面稀疏状态一直保持。查看重复索引SELECT pg_size_pretty(SUM(pg_relation_size(idx))::BIGINT) AS SIZE,       (array_agg(idx))[1] AS idx1, (array_agg(idx))[2] AS idx2,       (array_agg(idx))[3] AS idx3, (array_agg(idx))[4] AS idx4FROM (    SELECT indexrelid::regclass AS idx, (indrelid::text ||E'\n'|| indclass::text ||E'\n'|| indkey::text ||E'\n'||                                         COALESCE(indexprs::text,'')||E'\n' || COALESCE(indpred::text,'')) AS KEY    FROM pg_index) subGROUP BY KEY HAVING COUNT(*)>1ORDER BY SUM(pg_relation_size(idx)) DESC;表的大小和表中索引个数SELECT    t.tablename,    indexname,    c.reltuples AS num_rows,    pg_size_pretty(pg_relation_size(quote_ident(t.tablename)::text)) AS table_size,    pg_size_pretty(pg_relation_size(quote_ident(indexrelname)::text)) AS index_size,    CASE WHEN indisunique THEN 'Y'       ELSE 'N'    END AS UNIQUE,    idx_scan AS number_of_scans,    idx_tup_read AS tuples_read,    idx_tup_fetch AS tuples_fetchedFROM pg_tables tLEFT OUTER JOIN pg_class c ON t.tablename=c.relnameLEFT OUTER JOIN    ( SELECT c.relname AS ctablename, ipg.relname AS indexname, x.indnatts AS number_of_columns, idx_scan, idx_tup_read, idx_tup_fetch, indexrelname, indisunique FROM pg_index x           JOIN pg_class c ON c.oid = x.indrelid           JOIN pg_class ipg ON ipg.oid = x.indexrelid           JOIN pg_stat_all_indexes psai ON x.indexrelid = psai.indexrelid )    AS foo    ON t.tablename = foo.ctablenameWHERE t.schemaname='public'ORDER BY 1,2;获取每个表的行数，索引和一些关于这些索引的信息（比较详细）SELECT    pg_class.relname,    pg_size_pretty(pg_class.reltuples::BIGINT) AS rows_in_bytes,    pg_class.reltuples AS num_rows,    COUNT(indexname) AS number_of_indexes,    CASE WHEN x.is_unique = 1 THEN 'Y'       ELSE 'N'    END AS UNIQUE,    SUM(CASE WHEN number_of_columns = 1 THEN 1              ELSE 0            END) AS single_column,    SUM(CASE WHEN number_of_columns IS NULL THEN 0             WHEN number_of_columns = 1 THEN 0             ELSE 1           END) AS multi_columnFROM pg_namespace LEFT OUTER JOIN pg_class ON pg_namespace.oid = pg_class.relnamespaceLEFT OUTER JOIN       (SELECT indrelid,           MAX(CAST(indisunique AS INTEGER)) AS is_unique       FROM pg_index       GROUP BY indrelid) x       ON pg_class.oid = x.indrelidLEFT OUTER JOIN    ( SELECT c.relname AS ctablename, ipg.relname AS indexname, x.indnatts AS number_of_columns FROM pg_index x           JOIN pg_class c ON c.oid = x.indrelid           JOIN pg_class ipg ON ipg.oid = x.indexrelid  )    AS foo    ON pg_class.relname = foo.ctablenameWHERE      pg_namespace.nspname='public'AND  pg_class.relkind = 'r'GROUP BY pg_class.relname, pg_class.reltuples, x.is_uniqueORDER BY 2;

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