Hello Yu Pu, Am 2005-01-23 16:34:44, schrieb Yu Pan: > I am developing a new "image" datatype in postgres which contains a binary > field for storing image data and some other fields for additional information > about the image, like size, resolution, etc. I was hoping that the clients can > saving their time by directly retrieving these information from the fields > without retrieving the whole image, that is, the time for reading these fields > should be constant with respect to the image size. However, the result shows Realy cool > that the time for direct retrieving of information from the fields of an image > datatype is still increasing with the size of the image. My explanation is > that in order to read the fields of a image datatype, the whole struct would > still need to be loaded into memory, which includes the binary field > containing the actual image data. Can anyone tell me is this true for a user- > defined datatype (using C struct)? Thanks a lot. No, thats not right. An Image is a Header (image type, width, height, rawsize, colortable) plus the Data In most cases the Header is between 20 and 300 Bytes But which data do you need exactly ? I have done this in Winword 6.0 under WfW 3.11 for 10 years :-) You need only the first Bytes not the whole Image. > Yu Greetings Michelle -- Linux-User #280138 with the Linux Counter, http://counter.li.org/ Michelle Konzack Apt. 917 ICQ #328449886 50, rue de Soultz MSM LinuxMichi 0033/3/88452356 67100 Strasbourg/France IRC #Debian (irc.icq.com)
Attachment:
signature.pgp
Description: Digital signature
