char type seems the same as char(1)
От | Tom Lane |
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Тема | char type seems the same as char(1) |
Дата | |
Msg-id | 28655.912017111@sss.pgh.pa.us обсуждение исходный текст |
Ответы |
Re: [SQL] char type seems the same as char(1)
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Список | pgsql-sql |
The Postgres documentation (chapter "Data Types" in the User's Manual) states that type char is a single byte, whereas char(n) requires 4+n bytes. Some experimentation, however, shows that "char" is actually equivalent to char(1) --- it takes 5 bytes to store, even though psql's "\d table" command lies and claims it takes only 1. Worse, the field requires 4-byte alignment, which means if you have several of them in a row, it's costing you 8 bytes apiece. Is this a documentation error, or a code bug? If not a bug, is there any other way to store a character as a single-byte field? I'm currently using char fields all over the place as "poor man's enumerated type" values, and I'm rather annoyed to find that what I thought was taking 1 byte per field is actually taking 8... regards, tom lane
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