Базовые различия при работе с базами данными MySQL и PostgreSQL Дилетантский обзор

[TyVik]

Насчёт пункта 3 есть \x auto — когда помещается будет колоночный вывод, в противном случае построчный. Вообще проще всего написать для себя файлик .psqlrc. У меня он примерно такого содержимого:

\set COMP_KEYWORD_CASE upper
\x auto
\pset null ¤

Psql по сравнению со всеми остальными подобными консольными утилитами просто небо и земля. Вот хорошая статья с примерами использования.

[UUSER]

Основное бесиво, это реакция mysql консоли на Ctrl+C, когда хочется начать использовать это :)

psqlrc забыл:

\set QUIET 1
-- formatting
\x auto

\set VERBOSITY verbose
\set ON_ERROR_ROLLBACK interactive
-- show execution times
\timing
-- limit paging
\pset pager off
-- replace nulls
\pset null ¤
\pset linestyle unicode
\pset border 2

-- colorize
--\set PROMPT1 '%[%033[33;1m%]%x%[%033[0m%]%[%033[1m%]%/%[%033[0m%]%R%# '
\set PROMPT1 '%[%033[1m%]%M %n@%/%R%[%033[0m%]%# '
--harolds
--\set PROMPT1 '%[%033[1m%]%M/%/%R%[%033[0m%]%# '
\set PROMPT2 '[more] %R > '



--logging
-- Use a separate history file per-database.
\set HISTFILE ~/.psql_history- :DBNAME
-- If a command is run more than once in a row, only store it once in the
-- history.
\set HISTCONTROL ignoredups

-- Autocomplete keywords (like SELECT) in upper-case, even if you started
-- typing them in lower case.
\set COMP_KEYWORD_CASE upper

-- greeting needs to know where we are
-- \echo '\nWelcome, my magistrate\n'

\set clear '\\! clear;'

--helpful queries
\set uptime 'select now() - backend_start as uptime from pg_stat_activity where pid = pg_backend_pid();'
\set show_slow_queries 'SELECT (total_time / 1000 / 60) as total_minutes, (total_time/calls) as average_time, query FROM pg_stat_statements ORDER BY 1 DESC LIMIT 100;'
\set settings 'select name, setting,unit,context from pg_settings;'
\set conninfo 'select usename, count(*) from pg_stat_activity group by usename;'
\set activity 'select datname, pid, usename, application_name,client_addr, client_hostname, client_port, query, state from pg_stat_activity;'
\set waits 'SELECT pg_stat_activity.pid, pg_stat_activity.query, pg_stat_activity.waiting, now() - pg_stat_activity.query_start AS \"totaltime\", pg_stat_activity.backend_start FROM pg_stat_activity WHERE pg_stat_activity.query !~ \'%IDLE%\'::text AND pg_stat_activity.waiting = true;'
\set dbsize 'SELECT datname, pg_size_pretty(pg_database_size(datname)) db_size FROM pg_database ORDER BY db_size;'
\set tablesize 'SELECT nspname || \'.\' || relname AS \"relation\", pg_size_pretty(pg_relation_size(C.oid)) AS "size" FROM pg_class C LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace) WHERE nspname NOT IN (\'pg_catalog\', \'information_schema\') ORDER BY pg_relation_size(C.oid) DESC LIMIT 40;'
\set uselesscol 'SELECT nspname, relname, attname, typname, (stanullfrac*100)::int AS null_percent, case when stadistinct >= 0 then stadistinct else abs(stadistinct)*reltuples end AS \"distinct\", case 1 when stakind1 then stavalues1 when stakind2 then stavalues2 end AS \"values\" FROM pg_class c JOIN pg_namespace ns ON (ns.oid=relnamespace) JOIN pg_attribute ON (c.oid=attrelid) JOIN pg_type t ON (t.oid=atttypid) JOIN pg_statistic ON (c.oid=starelid AND staattnum=attnum) WHERE nspname NOT LIKE E\'pg\\\\_%\' AND nspname != \'information_schema\' AND relkind=\'r\' AND NOT attisdropped AND attstattarget != 0 AND reltuples >= 100 AND stadistinct BETWEEN 0 AND 1 ORDER BY nspname, relname, attname;'


-- 4 helpful queries from radek http://radek.cc/2009/08/15/psqlrc-tricks-table-sizes/
\set trashindexes '( select s.schemaname as sch, s.relname as rel, s.indexrelname as idx, s.idx_scan as scans, pg_size_pretty(pg_relation_size(s.relid)) as ts, pg_size_pretty(pg_relation_size(s.indexrelid)) as "is" from pg_stat_user_indexes s join pg_index i on i.indexrelid=s.indexrelid left join pg_constraint c on i.indrelid=c.conrelid and array_to_string(i.indkey, '' '') = array_to_string(c.conkey, '' '') where i.indisunique is false and pg_relation_size(s.relid) > 1000000 and s.idx_scan < 100000 and c.confrelid is null order by s.idx_scan asc, pg_relation_size(s.relid) desc );'
\set missingindexes '( select src_table, dst_table, fk_name, pg_size_pretty(s_size) as s_size, pg_size_pretty(d_size) as d_size, d from ( select distinct on (1,2,3,4,5) textin(regclassout(c.conrelid)) as src_table, textin(regclassout(c.confrelid)) as dst_table, c.conname as fk_name, pg_relation_size(c.conrelid) as s_size, pg_relation_size(c.confrelid) as d_size, array_upper(di.indkey::int[], 1) + 1 - array_upper(c.conkey::int[], 1) as d from pg_constraint c left join pg_index di on di.indrelid = c.conrelid and array_to_string(di.indkey, '' '') ~ (''^'' || array_to_string(c.conkey, '' '') || ''( |$)'') join pg_stat_user_tables st on st.relid = c.conrelid where c.contype = ''f'' order by 1,2,3,4,5,6 asc) mfk where mfk.d is distinct from 0 and mfk.s_size > 1000000 order by mfk.s_size desc, mfk.d desc );'
\set rtsize '(select table_schema, table_name, pg_relation_size( quote_ident( table_schema ) || \'.\' || quote_ident( table_name ) ) as size, pg_total_relation_size( quote_ident( table_schema ) || \'.\' || quote_ident( table_name ) ) as total_size  from information_schema.tables where table_type = \'BASE TABLE\' and table_schema not in (\'information_schema\', \'pg_catalog\') order by pg_relation_size( quote_ident( table_schema ) || \'.\' || quote_ident( table_name ) ) desc, table_schema, table_name);'
\set tsize '(select table_schema, table_name, pg_size_pretty(size) as size, pg_size_pretty(total_size) as total_size from (:rtsize) x order by x.size desc, x.total_size desc, table_schema, table_name);'


-- Taken from https://github.com/heroku/heroku-pg-extras
-- via https://github.com/dlamotte/dotfiles/blob/master/psqlrc
\set bloat 'SELECT tablename as table_name, ROUND(CASE WHEN otta=0 THEN 0.0 ELSE sml.relpages/otta::numeric END,1) AS table_bloat, CASE WHEN relpages < otta THEN ''0'' ELSE pg_size_pretty((bs*(sml.relpages-otta)::bigint)::bigint) END AS table_waste, iname as index_name, ROUND(CASE WHEN iotta=0 OR ipages=0 THEN 0.0 ELSE ipages/iotta::numeric END,1) AS index_bloat, CASE WHEN ipages < iotta THEN ''0'' ELSE pg_size_pretty((bs*(ipages-iotta))::bigint) END AS index_waste 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 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 CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::bigint END DESC;'
\set blocking 'select bl.pid as blocked_pid, ka.query as blocking_statement, now() - ka.query_start as blocking_duration, kl.pid as blocking_pid, a.query as blocked_statement, now() - a.query_start as blocked_duration from pg_catalog.pg_locks bl join pg_catalog.pg_stat_activity a on bl.pid = a.pid join pg_catalog.pg_locks kl join pg_catalog.pg_stat_activity ka on kl.pid = ka.pid on bl.transactionid = kl.transactionid and bl.pid != kl.pid where not bl.granted;'
\set cache_hit 'SELECT ''index hit rate'' as name, (sum(idx_blks_hit)) / sum(idx_blks_hit + idx_blks_read) as ratio FROM pg_statio_user_indexes union all SELECT ''cache hit rate'' as name, sum(heap_blks_hit) / (sum(heap_blks_hit) + sum(heap_blks_read)) as ratio FROM pg_statio_user_tables;'
\set index_size 'SELECT relname AS name, pg_size_pretty(sum(relpages*1024)) AS size FROM pg_class WHERE reltype=0 GROUP BY relname ORDER BY sum(relpages) DESC;'
\set index_usage 'SELECT relname, CASE idx_scan WHEN 0 THEN ''Insufficient data'' ELSE (100 * idx_scan / (seq_scan + idx_scan))::text END percent_of_times_index_used, n_live_tup rows_in_table FROM pg_stat_user_tables ORDER BY n_live_tup DESC;'
\set index_usage_adv 'SELECT * FROM (SELECT stat.relname AS table, stai.indexrelname AS index, CASE stai.idx_scan WHEN 0 THEN ''Insufficient data'' ELSE (100 * stai.idx_scan / (stat.seq_scan + stai.idx_scan))::text || ''%'' END hit_rate, CASE stat.idx_scan WHEN 0 THEN ''Insufficient data'' ELSE (100 * stat.idx_scan / (stat.seq_scan + stat.idx_scan))::text || ''%'' END all_index_hit_rate, ARRAY(SELECT pg_get_indexdef(idx.indexrelid, k + 1, true) FROM generate_subscripts(idx.indkey, 1) AS k ORDER BY k) AS cols, stat.n_live_tup rows_in_table FROM pg_stat_user_indexes AS stai JOIN pg_stat_user_tables AS stat ON stai.relid = stat.relid JOIN pg_index AS idx ON (idx.indexrelid = stai.indexrelid)) AS sub_inner ORDER BY rows_in_table DESC, hit_rate ASC;'
\set locks 'select pg_stat_activity.pid, pg_class.relname, pg_locks.transactionid, pg_locks.granted, substr(pg_stat_activity.query,1,30) as query_snippet, age(now(),pg_stat_activity.query_start) as "age" from pg_stat_activity,pg_locks left outer join pg_class on (pg_locks.relation = pg_class.oid) where pg_stat_activity.query <> ''<insufficient privilege>'' and pg_locks.pid=pg_stat_activity.pid and pg_locks.mode = ''ExclusiveLock'' order by query_start;'
\set long_running_queries 'SELECT pid, now() - pg_stat_activity.query_start AS duration, query AS query FROM pg_stat_activity WHERE pg_stat_activity.query <> ''''::text AND now() - pg_stat_activity.query_start > interval ''5 minutes'' ORDER BY now() - pg_stat_activity.query_start DESC;'
\set ps 'select pid, application_name as source, age(now(),query_start) as running_for, waiting, query as query from pg_stat_activity where query <> ''<insufficient privilege>'' AND state <> ''idle'' and pid <> pg_backend_pid() order by 3 desc;'
\set seq_scans 'SELECT relname AS name, seq_scan as count FROM pg_stat_user_tables ORDER BY seq_scan DESC;'
\set total_index_size 'SELECT pg_size_pretty(sum(relpages*1024)) AS size FROM pg_class WHERE reltype=0;'
\set unused_indexes 'SELECT schemaname || ''.'' || relname AS table, indexrelname AS index, pg_size_pretty(pg_relation_size(i.indexrelid)) AS index_size, idx_scan as index_scans FROM pg_stat_user_indexes ui JOIN pg_index i ON ui.indexrelid = i.indexrelid WHERE NOT indisunique AND idx_scan < 50 AND pg_relation_size(relid) > 5 * 8192 ORDER BY pg_relation_size(i.indexrelid) / nullif(idx_scan, 0) DESC NULLS FIRST, pg_relation_size(i.indexrelid) DESC;'
\set missing_indexes 'SELECT relname, seq_scan-idx_scan AS too_much_seq, case when seq_scan-idx_scan > 0 THEN ''Missing Index?'' ELSE ''OK'' END, pg_relation_size(relname::regclass) AS rel_size, seq_scan, idx_scan FROM pg_stat_all_tables WHERE schemaname=''public'' AND pg_relation_size(relname::regclass) > 80000 ORDER BY too_much_seq DESC;'

-- Development queries

\set sp 'SHOW search_path;'
\set clear '\\! clear;'
\set ll '\\! ls -lrt;'

\unset QUIET

[TyVik]

Ох ты ж блин, огромное тебе спасибо!

[bizzonaru]

Согласен, но не совсем. Я рассматриваю сравнение с точки зрения программиста. Для прикладного уровня проекта в принципе да, не имеет значение какая база данных. Под прикладным я понимаю, взять простым запросом небольшое количество данных и нарисовать в табличной форме. Другой вопрос, когда такая таблица из разряда middle/big table, то тут уже нужно понимать как строится запрос на уровне базы данных, как хранятся данные.

[VolCh]

С точки зрения программиста различий в посте не указано.