RE: PostgreSQL and mySQL database size question
От | Fred Ingham |
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Тема | RE: PostgreSQL and mySQL database size question |
Дата | |
Msg-id | PNEJKLGAKBJECOKMAOPHCEDFCPAA.ingham@erols.com обсуждение исходный текст |
Ответ на | Re: PostgreSQL and mySQL database size question (Bruce Momjian <pgman@candle.pha.pa.us>) |
Ответы |
Re: PostgreSQL and mySQL database size question
(Jan Wieck <JanWieck@Yahoo.com>)
|
Список | pgsql-general |
OK, but that only accounts for 3.2MB of the extra 49.6MB used by PostgreSQL. -----Original Message----- From: Bruce Momjian [mailto:pgman@candle.pha.pa.us] Sent: Friday, April 27, 2001 2:05 PM To: ingham@erols.com Cc: pgsql-general@postgresql.org Subject: Re: [GENERAL] PostgreSQL and mySQL database size question FAQ item 4.7 discusses table size computations. My guess is that it is the 36 bytes-per-row that is the problem. Those bytes record the visibility of the row for proper transactions semantics and MVCC. > Bruce, > > I have your book right in front of me... do you have that information in the > book? If not, I will take a look at the FAQ. As for mySQL, here are the > storage requirements: > > Storage requirements for numeric types > > Column type Storage required > TINYINT 1 byte > SMALLINT 2 bytes > MEDIUMINT 3 bytes > INT 4 bytes > INTEGER 4 bytes > BIGINT 8 bytes > FLOAT(X) 4 if X <= 24 or 8 if 25 <= X <= 53 > FLOAT 4 bytes > DOUBLE 8 bytes > DOUBLE PRECISION 8 bytes > REAL 8 bytes > DECIMAL(M,D) M+2 bytes if D > 0, M+1 bytes if D = 0 (D+2, if M < D) > NUMERIC(M,D) M+2 bytes if D > 0, M+1 bytes if D = 0 (D+2, if M < D) > > Storage requirements for date and time types > > Column type Storage required > DATE 3 bytes > DATETIME 8 bytes > TIMESTAMP 4 bytes > TIME 3 bytes > YEAR 1 byte > > Storage requirements for string types > > Column type Storage required > > CHAR(M) M bytes, 1 <= M <= 255 > VARCHAR(M) L+1 bytes, where L <= M and 1 <= M <= 255 > TINYBLOB, > TINYTEXT L+1 bytes, where L < 2^8 > BLOB, TEXT L+2 bytes, where L < 2^16 > MEDIUMBLOB, > MEDIUMTEXT L+3 bytes, where L < 2^24 > LONGBLOB, > LONGTEXT L+4 bytes, where L < 2^32 > ENUM('value1','value2',...) 1 or 2 bytes, depending on the number of > enumeration values (65535 values maximum) > SET('value1','value2',...) 1, 2, 3, 4 or 8 bytes, depending on the number of > set members (64 members maximum) > > Fred > > -----Original Message----- > From: Bruce Momjian [mailto:pgman@candle.pha.pa.us] > Sent: Friday, April 27, 2001 1:48 PM > To: ingham@erols.com > Cc: pgsql-general@postgresql.org > Subject: Re: [GENERAL] PostgreSQL and mySQL database size question > > > Did you see the FAQ items on estimating database sizes? Does MySQL have > less overhead per row? > > -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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