【发布时间】：2016-09-27 10:51:34
【问题描述】：
我有一个非常慢的查询，我不知道为什么，每个连接字段都有索引。
这是我的查询：
SELECT
CASE
WHEN
arrears_action.executed IS NULL
OR arrears_action.executed != '0000-00-00 00:00:00'
THEN
'No action'
ELSE DATE_FORMAT(arrears_action.planned, '%d %M %Y')
END,
CASE
WHEN
arrears_action.executed IS NULL
OR arrears_action.executed != '0000-00-00 00:00:00'
THEN
NULL
ELSE IF(DATEDIFF(NOW(), arrears_action.planned) >= 0,
DATEDIFF(NOW(), arrears_action.planned),
NULL)
END,
customer.id AS customer_id,
customer.customer_number AS cif_number,
arrears_application.id AS arrears_application_id,
person.id AS person_id,
person.fullname,
account.account_number,
CONCAT(branch.branch_id,
product.code,
SUBSTRING(contract.loan_number, - 9, 9)) AS loan_account,
payment.principal_amount_outstanding,
arrears.amount_in_arrears,
arrears.days_in_arrears,
balance.account_balance_available,
product.code AS product_code,
division.name AS division_name,
coll_customer_status.name AS customer_status,
loan_status.name AS loan_status
FROM
cregora_cregora.base_cregora_loancontract_inarrears_data AS arrears
INNER JOIN
cregora_cregora.base_cregora_loancontract_data AS contract ON contract.id = arrears.loancontract_id
INNER JOIN
cregora_cregora.base_cregora_loancontract_payment_data AS payment ON payment.loancontract_id = contract.id
INNER JOIN
cregora_cregora.base_cregora_nmb_product_class_data AS product ON product.id = contract.product_class
INNER JOIN
cregora_cregora.base_cregora_account_data AS account ON account.id = contract.account_id
INNER JOIN
cregora_cregora.base_cregora_customer_data AS customer ON customer.id = account.customer_id
INNER JOIN
cregora_cregora.base_cregora_person_data AS person ON person.id = customer.type_of_customer_id
INNER JOIN
cregora_base.system_organization_division AS division ON division.id = contract.loan_branch
INNER JOIN
cregora_cregora.base_cregora_nmb_branch_data AS branch ON branch.id = division.entity_instance_id
INNER JOIN
cregora_cregora.base_cregora_account_balanceinfo_daily_data AS balance ON balance.account_id = account.id
LEFT JOIN
cregora_cregora.base_cregora_arrears_applications_data AS arrears_application ON arrears_application.loan_contract_number = contract.loan_number
LEFT JOIN
cregora_cregora.base_cregora_arrears_action_data AS arrears_action ON arrears_action.arrears_application_id = arrears_application.id
LEFT JOIN
cregora_cregora.base_cregora_collection_applications_data AS coll_application ON coll_application.arrears_application_id = arrears_application.id
LEFT JOIN
cregora_cregora.base_cregora_collection_customer_statuses_data AS coll_customer_status ON coll_customer_status.id = coll_application.collection_customer_status_id
LEFT JOIN
cregora_cregora.base_cregora_arrears_loan_contract_statuses_data AS loan_status ON loan_status.id = arrears_application.loan_contract_status_id
LEFT JOIN
cregora_cregora.base_cregora_arrears_application_statuses_data AS arrears_status ON arrears_status.id = arrears_application.arrears_application_status_id
WHERE
contract.loan_branch IN (46)
AND (coll_customer_status.id IN ('1' , '2',
'3',
'5',
'6',
'7',
'8',
'9',
'10',
'11',
'12',
'13',
'15',
'16',
'17',
'18',
'19',
'20',
'21',
'22',
'23')
OR coll_customer_status.id IS NULL)
AND (loan_status.id IS NULL
OR loan_status.id IN ('1' , '2', '3', '4', '5'))
AND arrears.amount_in_arrears > '1'
GROUP BY arrears_application.id
ORDER BY arrears.days_in_arrears DESC , person.fullname
这是 EXPLAIN 的输出： 为什么mysql不使用合约表的任何索引（第三行解释，type-> ALL，可能的键->PRIMARY,account_id,loan_branch,product_class key->empty？
提前谢谢
【问题讨论】：
-
您能否让您的解释更具可读性。它可能没有使用索引，原因很简单，因为它不需要！为什么你担心它是查询慢？如果是这样，请给出时间并指出每个表中的行数
-
使用图片而不是文本输出，如您所见，合同表未使用任何索引。它正在执行全表扫描。我还不确定记录的数量，因为我仍在导入实际的测试数据，但有很多。在生产中，此查询将运行 5 分钟左右。附加说明：当删除 group by 和 order by 子句时，查询下降到一秒以下
-
在大型导入操作已在运行时进行任何类型的分析毫无意义
-
是的，我知道，但是其他团队成员也进行了分析，所以我们知道查询运行了很长时间，并且它正在导入到我的本地数据库，顺便说一句不是生产，所以不是
-
show variables like 'optimizer_search_depth';的输出是什么？
标签： mysql indexing database-performance