Обсуждение: varchar vs. text
Is there any good reason to use VARCHAR over TEXT for a string field? ie. performance hits, etc. Other than running into the row size limit problem, are there any large storage / performance penalties of using TEXT for virtually all strings? For ex. A phone number. This field probably wouldn't be bigger that 40 characters, but I can use TEXT and be sure that nothing gets truncated. Same with a "name" field. -rchit
Rachit Siamwalla <rachit@ensim.com> writes:
> Is there any good reason to use VARCHAR over TEXT for a string field?
The only reason to use VARCHAR is if you *want* the data to be truncated
at a specific length. If you don't have a well-defined upper limit in
mind, I'd recommend TEXT.
regards, tom lane
Rachit Siamwalla wrote: > > Is there any good reason to use VARCHAR over TEXT for a string field? ie. > performance hits, etc. > > Other than running into the row size limit problem, are there any large > storage / performance penalties of using TEXT for virtually all strings? Er - what kind of "row size limit"? I remember vaguely that there was something the like in ancient releases, but forgot the specific restrictions. Jan -- #======================================================================# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #================================================== JanWieck@Yahoo.com # _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com
On Wed, Jul 11, 2001 at 09:56:27AM -0400, Jan Wieck wrote: > Rachit Siamwalla wrote: > > > > Is there any good reason to use VARCHAR over TEXT for a string field? ie. > > performance hits, etc. > > > > Other than running into the row size limit problem, are there any large > > storage / performance penalties of using TEXT for virtually all strings? > > Er - what kind of "row size limit"? I remember vaguely that > there was something the like in ancient releases, but forgot > the specific restrictions. <FX: Sound of Jan whistling, looking around innocently> Very good Jan. Yes, PostgreSQL certainly develops on Internet time, and while TOAST may seem ancient news to you, it was only in the 7.1 release (2001-04-13). Three months is a little early to start the 'Problem? What problem?' campaign. Especially since some of the client libs (OBDC) just caught up, last week. :-) What Jan is so innocently not saying is described here: http://www.ca.postgresql.org/projects/devel-toast.html Jan not only solved the 'row size limit', he did it in a more general way, solving lots of the follow on problems that come from putting large fields into a table. Details at the above URL. Ross
Still can't index those large toasted items -- not that I want to. One interesting aspect is versioning of text documents where you want them to be UNIQUE in regards to book development otherwise you have the same document with 2 or more entries (more than a single version number). Poor example; I know. -- Rod Taylor Your eyes are weary from staring at the CRT. You feel sleepy. Notice how restful it is to watch the cursor blink. Close your eyes. The opinions stated above are yours. You cannot imagine why you ever felt otherwise. ----- Original Message ----- From: "Ross J. Reedstrom" <reedstrm@rice.edu> To: "Jan Wieck" <JanWieck@Yahoo.com> Cc: "Rachit Siamwalla" <rachit@ensim.com>; <pgsql-hackers@postgresql.org> Sent: Wednesday, July 11, 2001 10:56 AM Subject: Re: [HACKERS] varchar vs. text > On Wed, Jul 11, 2001 at 09:56:27AM -0400, Jan Wieck wrote: > > Rachit Siamwalla wrote: > > > > > > Is there any good reason to use VARCHAR over TEXT for a string field? ie. > > > performance hits, etc. > > > > > > Other than running into the row size limit problem, are there any large > > > storage / performance penalties of using TEXT for virtually all strings? > > > > Er - what kind of "row size limit"? I remember vaguely that > > there was something the like in ancient releases, but forgot > > the specific restrictions. > > <FX: Sound of Jan whistling, looking around innocently> > > Very good Jan. Yes, PostgreSQL certainly develops on Internet time, and > while TOAST may seem ancient news to you, it was only in the 7.1 release > (2001-04-13). Three months is a little early to start the 'Problem? What > problem?' campaign. Especially since some of the client libs (OBDC) > just caught up, last week. :-) > > What Jan is so innocently not saying is described here: > > http://www.ca.postgresql.org/projects/devel-toast.html > > Jan not only solved the 'row size limit', he did it in a more general > way, solving lots of the follow on problems that come from putting large > fields into a table. Details at the above URL. > > Ross > > ---------------------------(end of broadcast)--------------------------- > TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/users-lounge/docs/faq.html >
Ross J. Reedstrom wrote: > On Wed, Jul 11, 2001 at 09:56:27AM -0400, Jan Wieck wrote: > > Rachit Siamwalla wrote: > > > > > > Is there any good reason to use VARCHAR over TEXT for a string field? ie. > > > performance hits, etc. > > > > > > Other than running into the row size limit problem, are there any large > > > storage / performance penalties of using TEXT for virtually all strings? > > > > Er - what kind of "row size limit"? I remember vaguely that > > there was something the like in ancient releases, but forgot > > the specific restrictions. > > <FX: Sound of Jan whistling, looking around innocently> > > Very good Jan. Yes, PostgreSQL certainly develops on Internet time, and > while TOAST may seem ancient news to you, it was only in the 7.1 release > (2001-04-13). Three months is a little early to start the 'Problem? What > problem?' campaign. Especially since some of the client libs (OBDC) > just caught up, last week. :-) You're absotulely right, including the whistling ;-) I just couldn't resist, was too temping. And since I was sure there'll be more informative responses either way, whynot? Jan -- #======================================================================# # It's easier to get forgiveness for being wrong than for being right. # # Let's break this rule - forgive me. # #================================================== JanWieck@Yahoo.com # _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com