PostgreSQL 常用腳本

數據定義

資料庫

-- 創建資料庫
-- database_name，資料庫名稱
-- database_user，用戶名
CREATE DATABASE database_name WITH OWNER = database_user;
CREATE DATABASE database_name OWNER database_user;

-- 複製資料庫
-- database_name，資料庫名稱
-- database_user，用戶名
-- original_database_name，原始資料庫名稱
CREATE DATABASE database_name WITH TEMPLATE original_database_name OWNER database_user;

表

-- 新增列
-- table_name，表名
-- column_name，列名
ALTER TABLE table_name ADD COLUMN IF NOT EXISTS column_name VARCHAR(100) NULL;

擴展

-- 創建 UUID 擴展
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";

-- 驗證 UUID 擴展
SELECT uuid_generate_v4();

-- 創建 cube 擴展
CREATE EXTENSION IF NOT EXISTS cube;

-- 創建 earthdistance 擴展
CREATE EXTENSION IF NOT EXISTS earthdistance;

函數

-- 隱式將整形轉換成字元串，但是會有一些問題，參考 https://stackoverflow.com/questions/50025750/postgres-convert-integer-into-text。通常情況下還是建議使用 CAST 函數來實現。
-- 使用場景：在資料庫遷移的時候（比如 Microsoft SQL Server 轉成 PostgreSQL，Microsoft SQL Server 預設是支持的）需要隱式轉換，以達到快速實現的目的
CREATE FUNCTION pg_catalog.text(integer) RETURNS text STRICT IMMUTABLE LANGUAGE SQL AS 'SELECT textin(int4out($1));';
CREATE CAST (integer AS text) WITH FUNCTION pg_catalog.text(integer) AS IMPLICIT;
COMMENT ON FUNCTION pg_catalog.text(integer) IS 'convert integer to text';
CREATE FUNCTION pg_catalog.text(bigint) RETURNS text STRICT IMMUTABLE LANGUAGE SQL AS 'SELECT textin(int8out($1));';
CREATE CAST (bigint AS text) WITH FUNCTION pg_catalog.text(bigint) AS IMPLICIT;
COMMENT ON FUNCTION pg_catalog.text(bigint) IS 'convert bigint to text';

索引

-- Query the indexes of a table
SELECT * FROM pg_indexes WHERE tablename IN ('table_name');

-- 查詢所有索引
SELECT
    i.relname AS indname ,
    i.relowner AS indowner ,
    idx.indrelid::REGCLASS ,
    am.amname AS indam ,
    idx.indkey ,
    ARRAY(
    SELECT
        pg_get_indexdef(idx.indexrelid,
        k + 1,
        TRUE)
    FROM
        GENERATE_SUBSCRIPTS(idx.indkey, 1) AS k
    ORDER BY
        k) AS indkey_names ,
    idx.indexprs IS NOT NULL AS indexprs ,
    idx.indpred IS NOT NULL AS indpred
FROM
    pg_index AS idx
JOIN pg_class AS i ON
    i.oid = idx.indexrelid
JOIN pg_am AS am ON
    i.relam = am.oid
JOIN pg_namespace AS ns ON
    ns.oid = i.relnamespace
    AND ns.nspname = ANY (CURRENT_SCHEMAS(FALSE));

-- 查詢所有索引，排除系統表
SELECT
    U.usename AS user_name,
    ns.nspname AS schema_name,
    idx.indrelid :: REGCLASS AS table_name,
    i.relname AS index_name,
    idx.indisunique AS is_unique,
    idx.indisprimary AS is_primary,
    am.amname AS index_type,
    idx.indkey,
    ARRAY(
    SELECT
        pg_get_indexdef(idx.indexrelid,
        k + 1,
        TRUE)
    FROM
        GENERATE_SUBSCRIPTS(idx.indkey, 1) AS k
    ORDER BY
        k ) AS index_keys,
    (idx.indexprs IS NOT NULL)
    OR (idx.indkey::INT[] @> ARRAY[0]) AS is_functional,
    idx.indpred IS NOT NULL AS is_partial
FROM
    pg_index AS idx
JOIN pg_class AS i ON
    i.oid = idx.indexrelid
JOIN pg_am AS am ON
    i.relam = am.oid
JOIN pg_namespace AS NS ON
    i.relnamespace = NS.OID
JOIN pg_user AS U ON
    i.relowner = U.usesysid
WHERE
    NOT nspname LIKE 'pg%';

許可權控制

-- CREATE USER OR ROLE，PostgreSQL 中創建用戶和角色是等效的
-- role_name，用戶角色名稱
-- user_password，用戶密碼
-- user_name，用戶角色名稱
CREATE ROLE role_name WITH CREATEDB CREATEROLE LOGIN PASSWORD 'user_password';
CREATE user user_name PASSWORD 'user_password';

-- 分配所有許可權
-- database_name，資料庫名稱
-- database_user，資料庫用戶
GRANT ALL PRIVILEGES ON database_name TO database_user;

-- 修改表的 Owner
ALTER TABLE table_name OWNER TO database_user;

-- 分配 FUNCTION 的許可權給指定用戶
-- function_name，函數名稱
-- parameter1_type，第一個函數參數類型
-- parameter2_type，第二個函數參數類型
-- database_user，資料庫用戶
GRANT EXECUTE ON FUNCTION function_name(parameter1_type, parameter2_type, ...) TO database_user;

-- 修改 FUNCTION 的 Owner
-- function_name，函數名稱
-- parameter1_type，第一個函數參數類型
-- parameter2_type，第二個函數參數類型
-- database_user，資料庫用戶
ALTER FUNCTION function_name(parameter1_type, parameter2_type, ...) OWNER TO database_user;

運行分析

-- 查詢當前資料庫 TOP 20 大表
SELECT table_name
    ,pg_size_pretty(pg_relation_size(table_schema || '.' || table_name)) AS size
FROM information_schema.tables
ORDER BY pg_relation_size(table_schema || '.' || table_name) DESC LIMIT 20;

-- 查詢單個表大小
SELECT pg_size_pretty(pg_relation_size(table_name));

-- 查詢資料庫活動的查詢
SELECT current_timestamp - query_start AS runtime
    ,query_start
    ,datname
    ,pid
    ,query
FROM pg_stat_activity
WHERE query_start IS NOT NULL
ORDER BY 1 DESC limit 20;

運行維護

-- Cancel Processes by pid
SELECT pg_cancel_backend(pid int);

-- Terminate Processes by pid
SELECT pg_terminate_backend(pid int);

-- Kill all existing connections in the original database
-- source_db，資料庫名稱
SELECT pg_terminate_backend(pg_stat_activity.pid)
FROM pg_stat_activity
WHERE pg_stat_activity.datname = 'source_db'
AND pid <> pg_backend_pid();

-- garbage-collect and optionally analyze a database
-- table_name，資料庫表名
VACUUM table_name;
VACUUM FULL table_name;

配置

-- 修改 max_locks_per_transaction
ALTER SYSTEM SET max_locks_per_transaction = 300;

-- 重載配置信息，使配置生效
-- pg_hba.conf
SELECT pg_reload_conf();

備份還原

pg_dump -h host_name -U database_user -F c -b -v -f file_path database_name

pg_restore -h host_name -U database_user --no-owner -d database_name file_path

其他

-- Prepare a statement for execution
PREPARE foo(TEXT, TEXT, TEXT) AS
SELECT *
FROM foobar
WHERE foo = $1
    AND bar = $2
    OR baz = $3
EXECUTE foo('foo', 'bar', 'baz');
DEALLOCATE foo;

時間處理

-- 查詢時間差
SELECT EXTRACT(epoch FROM (begin_time - end_time));

-- Query the last month in format 'YYYYMM'
SELECT to_char(date_trunc('month', current_date - interval '1' month), 'YYYYMM');

psql

# 打開資料庫連接
psql -h host_name -U database_user

# 列出所有的資料庫
\l

# 連接數據
\c database_name