vti_encoding:SR|utf8-nl
vti_timelastmodified:TR|30 Aug 2002 04:23:07 -0000
vti_extenderversion:SR|5.0.2.4330
vti_title:SR|Life of a Minibase Query
vti_backlinkinfo:VX|openAccess/Minibase/intro/over3.more.html openAccess/Minibase/intro/single_user.html openAccess/Minibase/intro/over4.more.html
vti_nexttolasttimemodified:TR|30 Aug 2002 04:14:06 -0000
vti_author:SR|Administrator
vti_modifiedby:SR|Administrator
vti_timecreated:TR|30 Aug 2002 03:00:16 -0000
vti_shadowfiles:VX|
vti_lineageid:SR|{B3E82C71-098C-4532-BB3A-2C47154FA2DD}
vti_cacheddtm:TX|04 Nov 2003 21:40:14 -0000
vti_filesize:IR|5598
vti_cachedtitle:SR|Life of a Minibase Query
vti_cachedbodystyle:SR|
vti_cachedlinkinfo:VX|S|../gif/parch.jpg -H|../../../images/book3ed.jpg -S|../../../images/book3ed.jpg -H|http://www.cs.wisc.edu/~raghu -H|http://www.cs.cornell.edu/johannes -S|../../../images/hline.gif -H|../../../images/book3ed.jpg -S|../../../images/book3ed.jpg -H|http://www.cs.wisc.edu/~raghu -H|http://www.cs.cornell.edu/johannes -S|../../../images/hline.gif S|../gif/hline.gif H|../parser/parser.html H|../system/Catalog/catalog.html H|../optimizer/optimizer.html H|../system/Catalog/catalog.html H|../planner/planner.html H|../planner/iterator.html>iterators\\ (such\\ as\\ scans\\ and\\ joins)\\ that\\ will\\ actually\\ access\\ the\\ pages\\ of\\ the\\ database.\\ \\ Iteratorsreturn\\ tuples\\ when\\ get_next\\ is\\ called\\ on\\ them.Consider\\ this\\ query:
select\\ sailors.sname
from\\ sailors,\\ reserves
where\\ sailors.sid\\ =\\ reserves.sid;
A\\ sample\\ plan\\ tree\\ is\\ shown\\ below.\\ The\\ join\\ takes\\ two\\ scans\\ on\\ two\\ differentrelations\\ as\\ its\\ input.\\ \\ The\\ join\\ will\\ call\\ get_next\\ on\\ eachof\\ the\\ scan\\ iterators\\ as\\ tuples\\ are\\ needed.\\ \\ Filescans\\ are\\ used\\ becausewe\\ assume\\ that\\ no\\ matching\\ indexes\\ exist,\\ in\\ this\\ example.
iterators\\ (such\\ as\\ scans\\ and\\ joins)\\ that\\ will\\ actually\\ access\\ the\\ pages\\ of\\ the\\ database.\\ \\ Iteratorsreturn\\ tuples\\ when\\ get_next\\ is\\ called\\ on\\ them.Consider\\ this\\ query:
select\\ sailors.sname
from\\ sailors,\\ reserves
where\\ sailors.sid\\ =\\ reserves.sid;
A\\ sample\\ plan\\ tree\\ is\\ shown\\ below.\\ The\\ join\\ takes\\ two\\ scans\\ on\\ two\\ differentrelations\\ as\\ its\\ input.\\ \\ The\\ join\\ will\\ call\\ get_next\\ on\\ eachof\\ the\\ scan\\ iterators\\ as\\ tuples\\ are\\ needed.\\ \\ Filescans\\ are\\ used\\ becausewe\\ assume\\ that\\ no\\ matching\\ indexes\\ exist,\\ in\\ this\\ example.