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Re: text vs varchar
Posted by: Øystein Grøvlen ()
Date: May 02, 2016 04:37AM

Hi Rick,

No, I am referring to that when a row is read from storage engine into MySQL server, the size of the buffer allocated for the row is the maximum row size. However, only the column values that are actually needed will be copied into this buffer. So more memory will be allocated than if TEXT was used instead of VARCHAR.

I did not consider temporary tables in my answer since the question stated that such columns would only be fetched by look-up on primary key. If so, temporary tables should not apply. It is also the case that for temporary tables with VARCHAR(n) columns where n > 512, MEMORY will not be used. Hence, with respect to temporary tables, behavior should be the same regardless of whether column is VARCHAR(4000) and TEXT.

Øystein Grøvlen,
Senior Principal Software Engineer,
MySQL Group, Oracle,
Trondheim, Norway

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Subject Views Written By Posted
text vs varchar 798 hua kai 04/28/2016 08:36AM
Re: text vs varchar 407 Øystein Grøvlen 04/29/2016 12:41AM
Re: text vs varchar 413 Rick James 04/30/2016 11:51PM
Re: text vs varchar 447 Øystein Grøvlen 05/02/2016 04:37AM
Re: text vs varchar 386 hua kai 05/02/2016 09:14PM
Re: text vs varchar 385 Øystein Grøvlen 05/03/2016 02:19AM
Re: text vs varchar 604 hua kai 05/03/2016 04:12AM
Re: text vs varchar 371 hua kai 05/02/2016 08:02PM
Re: text vs varchar 489 Øystein Grøvlen 05/03/2016 02:25AM

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