好吧，你有大的表格，索引和長時間執行PG的平原。讓我們思考如何改進你的計劃和縮短時間。你寫和刪除行。 PG編寫和刪除元組以及表和索引可能會變得臃腫。爲了好搜索，PG將索引加載到共享緩衝區。你需要保持你的索引儘可能乾淨。對於選擇，PG將讀取到共享緩衝區而不是搜索。嘗試設置緩衝區內存並減少索引和表格膨脹，保持數據庫清理。
您做些什麼，想一想：
1）只要檢查指標重複，並具有很好的選擇，你的索引：
WITH table_scans as (
SELECT relid,
tables.idx_scan + tables.seq_scan as all_scans,
(tables.n_tup_ins + tables.n_tup_upd + tables.n_tup_del) as writes,
pg_relation_size(relid) as table_size
FROM pg_stat_user_tables as tables
),
all_writes as (
SELECT sum(writes) as total_writes
FROM table_scans
),
indexes as (
SELECT idx_stat.relid, idx_stat.indexrelid,
idx_stat.schemaname, idx_stat.relname as tablename,
idx_stat.indexrelname as indexname,
idx_stat.idx_scan,
pg_relation_size(idx_stat.indexrelid) as index_bytes,
indexdef ~* 'USING btree' AS idx_is_btree
FROM pg_stat_user_indexes as idx_stat
JOIN pg_index
USING (indexrelid)
JOIN pg_indexes as indexes
ON idx_stat.schemaname = indexes.schemaname
AND idx_stat.relname = indexes.tablename
AND idx_stat.indexrelname = indexes.indexname
WHERE pg_index.indisunique = FALSE
),
index_ratios AS (
SELECT schemaname, tablename, indexname,
idx_scan, all_scans,
round((CASE WHEN all_scans = 0 THEN 0.0::NUMERIC
ELSE idx_scan::NUMERIC/all_scans * 100 END),2) as index_scan_pct,
writes,
round((CASE WHEN writes = 0 THEN idx_scan::NUMERIC ELSE idx_scan::NUMERIC/writes END),2)
as scans_per_write,
pg_size_pretty(index_bytes) as index_size,
pg_size_pretty(table_size) as table_size,
idx_is_btree, index_bytes
FROM indexes
JOIN table_scans
USING (relid)
),
index_groups AS (
SELECT 'Never Used Indexes' as reason, *, 1 as grp
FROM index_ratios
WHERE
idx_scan = 0
and idx_is_btree
UNION ALL
SELECT 'Low Scans, High Writes' as reason, *, 2 as grp
FROM index_ratios
WHERE
scans_per_write <= 1
and index_scan_pct < 10
and idx_scan > 0
and writes > 100
and idx_is_btree
UNION ALL
SELECT 'Seldom Used Large Indexes' as reason, *, 3 as grp
FROM index_ratios
WHERE
index_scan_pct < 5
and scans_per_write > 1
and idx_scan > 0
and idx_is_btree
and index_bytes > 100000000
UNION ALL
SELECT 'High-Write Large Non-Btree' as reason, index_ratios.*, 4 as grp
FROM index_ratios, all_writes
WHERE
(writes::NUMERIC/(total_writes + 1)) > 0.02
AND NOT idx_is_btree
AND index_bytes > 100000000
ORDER BY grp, index_bytes DESC)
SELECT reason, schemaname, tablename, indexname,
index_scan_pct, scans_per_write, index_size, table_size
FROM index_groups;
2）檢查是否有表和索引腹脹？
SELECT
current_database(), schemaname, tablename, /*reltuples::bigint, relpages::bigint, otta,*/
ROUND((CASE WHEN otta=0 THEN 0.0 ELSE sml.relpages::FLOAT/otta END)::NUMERIC,1) AS tbloat,
CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::BIGINT END AS wastedbytes,
iname, /*ituples::bigint, ipages::bigint, iotta,*/
ROUND((CASE WHEN iotta=0 OR ipages=0 THEN 0.0 ELSE ipages::FLOAT/iotta END)::NUMERIC,1) AS ibloat,
CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta) END AS wastedibytes
FROM (
SELECT
schemaname, tablename, cc.reltuples, cc.relpages, bs,
CEIL((cc.reltuples*((datahdr+ma-
(CASE WHEN datahdr%ma=0 THEN ma ELSE datahdr%ma END))+nullhdr2+4))/(bs-20::FLOAT)) AS otta,
COALESCE(c2.relname,'?') AS iname, COALESCE(c2.reltuples,0) AS ituples, COALESCE(c2.relpages,0) AS ipages,
COALESCE(CEIL((c2.reltuples*(datahdr-12))/(bs-20::FLOAT)),0) AS iotta -- very rough approximation, assumes all cols
FROM (
SELECT
ma,bs,schemaname,tablename,
(datawidth+(hdr+ma-(CASE WHEN hdr%ma=0 THEN ma ELSE hdr%ma END)))::NUMERIC AS datahdr,
(maxfracsum*(nullhdr+ma-(CASE WHEN nullhdr%ma=0 THEN ma ELSE nullhdr%ma END))) AS nullhdr2
FROM (
SELECT
schemaname, tablename, hdr, ma, bs,
SUM((1-null_frac)*avg_width) AS datawidth,
MAX(null_frac) AS maxfracsum,
hdr+(
SELECT 1+COUNT(*)/8
FROM pg_stats s2
WHERE null_frac<>0 AND s2.schemaname = s.schemaname AND s2.tablename = s.tablename
) AS nullhdr
FROM pg_stats s, (
SELECT
(SELECT current_setting('block_size')::NUMERIC) AS bs,
CASE WHEN SUBSTRING(v,12,3) IN ('8.0','8.1','8.2') THEN 27 ELSE 23 END AS hdr,
CASE WHEN v ~ 'mingw32' THEN 8 ELSE 4 END AS ma
FROM (SELECT version() AS v) AS foo
) AS constants
GROUP BY 1,2,3,4,5
) AS foo
) AS rs
JOIN pg_class cc ON cc.relname = rs.tablename
JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname = rs.schemaname AND nn.nspname <> 'information_schema'
LEFT JOIN pg_index i ON indrelid = cc.oid
LEFT JOIN pg_class c2 ON c2.oid = i.indexrelid
) AS sml
ORDER BY wastedbytes DESC
3）您是否從硬盤清理未使用的元組？真空是時候了嗎？
SELECT
relname AS TableName
,n_live_tup AS LiveTuples
,n_dead_tup AS DeadTuples
FROM pg_stat_user_tables;
4）想一想。如果你在db中有10條記錄，而10中有8條id = 2，那麼這意味着你的索引選擇性不好，這樣PG就會掃描所有8條記錄。但是，你嘗試使用ID！= 2索引將工作良好。嘗試設置良好的選擇索引。
5）使用正確的列類型爲您提供數據。如果您可以使用較少的kb類型爲您的列轉換它。
6）只要檢查你的數據庫和條件。檢查這個開始page 只是試圖看到你有在數據庫中未使用的數據在表中，索引必須清理，檢查選擇性爲您的索引。嘗試使用其他brin索引數據，嘗試重新創建索引。
「cnt_contacts_idx_act_owner_id」索引的定義是什麼？ –
CREATE INDEX cnt_contacts_idx_act_owner_id ON public.cnt_contacts 使用btree（act_owner_id，status_id）; –
你應該創建另一個只有'act_owner_id'的索引。 – frlan