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jberkusjberkus
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added index usage queries and some notes.
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‎README.md‎

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@@ -52,6 +52,11 @@ duplicate_indexes_fuzzy.sql
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Check indexes and looks at whether or not they are potentially duplicates. It does this by checking the columns used by each index, so it reports lots of false duplicates for partial and functional indexes.
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needed_indexes.sql
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------------------
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Checks for tables which are getting too much sequential scan activity and might need additional indexing. Reports in four groups based on table size, number of scans, write activity, and number of existing indexes.
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Locks
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=====
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‎bloat/index_bloat_check.sql‎

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@@ -16,7 +16,7 @@ WITH btree_index_atts AS (
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JOIN pg_namespace ON pg_namespace.oid = indexclass.relnamespace
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JOIN pg_am ON indexclass.relam = pg_am.oid
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WHERE pg_am.amname = 'btree' and indexclass.relpages > 0
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--AND nspname NOT IN ('pg_catalog','information_schema')
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AND nspname NOT IN ('pg_catalog','information_schema')
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),
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index_item_sizes AS (
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SELECT
@@ -86,7 +86,7 @@ raw_bloat AS (
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),
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format_bloat AS (
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SELECT dbname as database_name, nspname as schema_name, table_name, index_name,
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round(realbloat) as bloat_pct, round(wastedbytes/(1024^2)::NUMERIC) as bloat_mb,
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round(realbloat) as \bloat_pct, round(wastedbytes/(1024^2)::NUMERIC) as bloat_mb,
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round(totalbytes/(1024^2)::NUMERIC,3) as index_mb,
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round(table_bytes/(1024^2)::NUMERIC,3) as table_mb,
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index_scans

‎indexes/needed_indexes.sql‎

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WITH
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write_adjust AS (
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-- change the below to 1.0 if pg_stats goes back to
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-- the creation of the database
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SELECT 0.0 AS adjustment
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),
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index_usage AS (
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SELECT sut.relid,
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current_database() AS database,
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sut.schemaname::text as schema_name,
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sut.relname::text AS table_name,
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sut.seq_scan as table_scans,
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sut.idx_scan as index_scans,
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pg_total_relation_size(relid) as table_bytes,
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round(sut.n_tup_ins + sut.n_tup_del + sut.n_tup_upd + sut.n_tup_hot_upd) /
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(seq_tup_read::NUMERIC + 2), 2) as writes_per_scan
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FROM pg_stat_user_tables sut,
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write_adjust
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),
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index_counts AS (
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SELECT sut.relid,
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count(*) as index_count
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FROM pg_stat_user_tables sut LEFT OUTER JOIN pg_indexes
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ON sut.schemaname = pg_indexes.schemaname AND
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sut.relname = pg_indexes.tablename
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GROUP BY relid
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),
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too_many_tablescans AS (
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SELECT 'many table scans'::TEXT as reason,
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database, schema_name, table_name,
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table_scans, pg_size_pretty(table_bytes) as table_size,
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writes_per_scan, index_count, table_bytes
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FROM index_usage JOIN index_counts USING ( relid )
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WHERE table_scans > 1000
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AND table_scans > ( index_scans * 2 )
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AND table_bytes > 32000000
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AND writes_per_scan < ( 1.0 )
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ORDER BY table_scans DESC
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),
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scans_no_index AS (
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SELECT 'scans, few indexes'::TEXT as reason,
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database, schema_name, table_name,
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table_scans, pg_size_pretty(table_bytes) as table_size,
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writes_per_scan, index_count, table_bytes
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FROM index_usage JOIN index_counts USING ( relid )
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WHERE table_scans > 100
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AND table_scans > ( index_scans )
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AND index_count < 2
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AND table_bytes > 32000000
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AND writes_per_scan < ( 1.0 )
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ORDER BY table_scans DESC
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),
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big_tables_with_scans AS (
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SELECT 'big table scans'::TEXT as reason,
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database, schema_name, table_name,
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table_scans, pg_size_pretty(table_bytes) as table_size,
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writes_per_scan, index_count, table_bytes
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FROM index_usage JOIN index_counts USING ( relid )
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WHERE table_scans > 100
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AND table_scans > ( index_scans / 10 )
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AND table_bytes > 1000000000
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AND writes_per_scan < ( 1.0 )
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ORDER BY table_bytes DESC
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),
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scans_no_writes AS (
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SELECT 'scans, no writes'::TEXT as reason,
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database, schema_name, table_name,
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table_scans, pg_size_pretty(table_bytes) as table_size,
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writes_per_scan, index_count, table_bytes
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FROM index_usage JOIN index_counts USING ( relid )
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WHERE table_scans > 100
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AND table_scans > ( index_scans / 4 )
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AND table_bytes > 32000000
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AND writes_per_scan < ( 0.1 )
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ORDER BY writes_per_scan ASC
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)
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SELECT reason, database, schema_name, table_name, table_scans,
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table_size, writes_per_scan, index_count
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FROM too_many_tablescans
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UNION ALL
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SELECT reason, database, schema_name, table_name, table_scans,
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table_size, writes_per_scan, index_count
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FROM scans_no_index
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UNION ALL
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SELECT reason, database, schema_name, table_name, table_scans,
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table_size, writes_per_scan, index_count
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FROM big_tables_with_scans
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UNION ALL
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SELECT reason, database, schema_name, table_name, table_scans,
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table_size, writes_per_scan, index_count
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FROM scans_no_writes;
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‎indexes/unused_indexes.sql‎

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WITH table_scans as (
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SELECT relid,
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tables.idx_scan + tables.seq_scan as all_scans,
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( tables.n_tup_ins + tables.n_tup_upd + tables.n_tup_del ) as writes,
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pg_relation_size(relid) as table_size
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FROM pg_stat_user_tables as tables
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),
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all_writes as (
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SELECT sum(writes) as total_writes
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FROM table_scans
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),
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indexes as (
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SELECT idx_stat.relid, idx_stat.indexrelid,
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idx_stat.schemaname, idx_stat.relname as tablename,
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idx_stat.indexrelname as indexname,
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idx_stat.idx_scan,
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pg_relation_size(idx_stat.indexrelid) as index_bytes,
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indexdef ~* 'USING btree' AS idx_is_btree
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FROM pg_stat_user_indexes as idx_stat
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JOIN pg_index
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USING (indexrelid)
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JOIN pg_indexes as indexes
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ON idx_stat.schemaname = indexes.schemaname
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AND idx_stat.relname = indexes.tablename
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AND idx_stat.indexrelname = indexes.indexname
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WHERE pg_index.indisunique = FALSE
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),
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index_ratios AS (
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SELECT schemaname, tablename, indexname,
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idx_scan, all_scans,
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round(( CASE WHEN all_scans = 0 THEN 0.0::NUMERIC
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ELSE idx_scan::NUMERIC/all_scans * 100 END),2) as index_scan_pct,
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writes,
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round((CASE WHEN writes = 0 THEN idx_scan::NUMERIC ELSE idx_scan::NUMERIC/writes END),2)
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as scans_per_write,
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pg_size_pretty(index_bytes) as index_size,
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pg_size_pretty(table_size) as table_size,
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idx_is_btree, index_bytes
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FROM indexes
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JOIN table_scans
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USING (relid)
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),
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index_groups AS (
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SELECT 'Never Used Indexes' as reason, *, 1 as grp
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FROM index_ratios
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WHERE
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idx_scan = 0
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and idx_is_btree
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UNION ALL
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SELECT 'Low Scans, High Writes' as reason, *, 2 as grp
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FROM index_ratios
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WHERE
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scans_per_write <= 1
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and index_scan_pct < 10
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and idx_scan > 0
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and writes > 100
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and idx_is_btree
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UNION ALL
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SELECT 'Seldom Used Large Indexes' as reason, *, 3 as grp
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FROM index_ratios
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WHERE
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index_scan_pct < 5
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and scans_per_write > 1
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and idx_scan > 0
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and idx_is_btree
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and index_bytes > 100000000
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UNION ALL
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SELECT 'High-Write Large Non-Btree' as reason, index_ratios.*, 4 as grp
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FROM index_ratios, all_writes
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WHERE
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( writes::NUMERIC / ( total_writes + 1 ) ) > 0.02
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AND NOT idx_is_btree
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AND index_bytes > 100000000
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ORDER BY grp, index_bytes DESC )
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SELECT reason, schemaname, tablename, indexname,
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index_scan_pct, scans_per_write, index_size, table_size
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FROM index_groups;

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