Add index to the field of existing data (Damon database version)

Add an index to the field of existing data

For fields with existing data , Some databases do not support adding indexes directly , Even if it supports a large amount of data, adding indexes directly is still easy to cause various problems , The safety factor is not high ... So I encounter this kind of scene , The more conservative way is to create exactly the same temporary table , First, add indexes to the fields of the temporary table that need to be indexed , Then insert the data into the temporary table , Finally, rename the temporary table to the original table . Temporary tables can be deleted or not , Data can also be backed up .

Example （ Need to give TB_EXCHANGE_LOG Tabular DATATYPE、STATE、PRIMARYID Add index to field ）：

1、 Export table creation statement , Execute the table creation statement after modifying the table name , for example

#  I am used to adding  temp
CREATE TABLE LN.TB_EXCHANGE_LOG_TEMP (
	ID NUMBER(38,0),
	XZQHDM VARCHAR2(512),
	PRIMARYID VARCHAR2(512),
	DATATYPE NUMBER(38,0),
	DATANAME VARCHAR2(200),
	REMARK VARCHAR2(100),
	STATE NUMBER(38,0),
	CREATETIME TIMESTAMP,
	PID VARCHAR(100),
	DESTINATION VARCHAR(100)
);

2、 Add indexes to the fields of the temporary table , for example

#  Index naming conventions recommendations  IDX1_ Field name  IDX2_ Field name   Adding the table name can avoid duplicate Index Names 
CREATE INDEX IDX1_DATATYPE ON LN.TB_EXCHANGE_LOG_TEMP(DATATYPE) TABLESPACE LN;
CREATE INDEX IDX2_STATE ON LN.TB_EXCHANGE_LOG_TEMP(STATE) TABLESPACE LN;
CREATE INDEX IDX3_PRIMARYID ON LN.TB_EXCHANGE_LOG_TEMP(PRIMARYID) TABLESPACE LN;

3、 Insert the data of the formal table into the temporary table , for example

INSERT INTO LN.TB_EXCHANGE_LOG_TEMP(ID, XZQHDM, PRIMARYID, DATATYPE, DATANAME, REMARK, 
STATE, CREATETIME, PID, DESTINATION) SELECT ID, XZQHDM, PRIMARYID, DATATYPE, DATANAME, REMARK, 
STATE, CREATETIME, PID, DESTINATION FROM LN.TB_EXCHANGE_LOG;

4、 Compare the number of records in the temporary table and the formal table , for example

SELECT COUNT(*) FROM LN.TB_EXCHANGE_LOG_TEMP;
SELECT COUNT(*) FROM LN.TB_EXCHANGE_LOG;

5、 Change the temporary table name to the formal table name

ALTER TABLE TB_EXCHANGE_LOG RENAME TO TB_EXCHANGE_LOG1;
ALTER TABLE TB_EXCHANGE_LOG_TEMP RENAME TO TB_EXCHANGE_LOG;
ALTER TABLE TB_EXCHANGE_LOG1 RENAME TO TB_EXCHANGE_LOG_TEMP;

OK, perfect .