![]() ![]() And you can always validate that your data is restricted to 7-bit ASCII for whatever legacy system you're having to maintain, even while enjoying some of the benefits of full Unicode storage. And you will be preparing for the future. Unicode avoids conversion problems when interfacing with other systems. The OS and database collation algorithms will work better with Unicode. If you are interfacing with an application that uses only ASCII, I would still recommend using Unicode in the database. UPDATES were done overnight (took a few hours). Afterwards I have manually executed UPDATE statements to set the new column value to true/false depending on other column values. The following SQL changes the data type of the column named BirthDate in the. I have added boolean type column to table with roughly 100 million rows. The ALTER COLUMN command is used to change the data type of a column in a table. And recovery from conversion errors is a non-trivial problem. Postgresql table size growth after adding column. Conversions take time, and are prone to errors. By using nvarchar rather than varchar, you can avoid doing encoding conversions every time you read from or write to the database. The default values only apply to subsequent INSERT commands they do not cause rows already in the. With cheap disk and memory nowadays, there is really no reason to waste time mucking around with code pages anymore.Īll modern operating systems and development platforms use Unicode internally. These forms set or remove the default value for a column. Codepage incompatabilities are a pain, and Unicode is the cure for codepage problems. I believe this is not the correct answer. Some people think that varchar should be used because it takes up less space. A varchar column is restricted to an 8-bit codepage. When you invoke ADD COLUMN, all existing rows in the table are initialized with the columns default value (null if no DEFAULT clause is specified). Postgres-> from information_schema.An nvarchar column can store any Unicode data. Postgres=> select 'alter table '||table_schema||'.'||table_name||' alter column '||column_name||' type text ' Run the above statement, spool the output into a text file, then run the generated script. Replace 'public' with your schema if your tables are not located in the public schema. You can use the following statement to generate the needed ALTER TABLE statements: select 'alter table '||table_schema||'.'||table_name||' alter column '||column_name||' type text ' I guess you don't want to manually run all the necessary ALTER TABLE statements. Commands of the form: ALTER TABLE fooĭynamic UPDATE fails due to unwanted parenthesis around string in plpgsql If there can be multiple, it would be substantially cheaper to execute all type changes in a single ALTER TABLE statement per table. In your particular case, there can only be one column per table. demonstrates the other good option to use the information schema instead. I build command from the system catalogs. This changes the type for all columns description varchar(255), except for those in system catalogs, temporary tables (both starting with 'pg_') and the information schema. After confirming the commands are sane, switch the comment characters - to actually execute the DDL commands. Since the command is potentially hazardous I commented the EXECUTE and put a RAISE NOTICE there instead. ![]() JOIN pg_namespace n ON n.oid = c.relnamespaceĪND NOT a.attisdropped - no dropped columnsĪND a.attnum > 0 - no system columns (redundant check)ĪND format_type(a.atttypid, a.atttypmod) = 'character varying(255)'ĪND n.nspname NOT LIKE ALL (''::text) , a.attrelid::regclass, a.attname), E' \n') SELECT string_agg(format('ALTER TABLE %s ALTER COLUMN %I TYPE text' You can use a DO statement to run a single dynamic command: DO ![]()
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