Thanks a lot Richard for your help. I apologize for not including the script. I will make it a point to add the scripts from hereon.
On Fri, Sep 19, 2014 at 10:30 AM, Richard Hipp <d...@sqlite.org> wrote: > You start by presenting us with a stand-alone script that we can run to see > your question. See you are getting free help, you really should be > striving to make it easy for people to help you. We don't have a script > from you, so I made one up. I'm using: > > CREATE TABLE employee(eid INTEGER PRIMARY KEY, name TEXT); > CREATE TABLE location(lid INTEGER PRIMARY KEY, name TEXT); > CREATE TABLE company(cid INTEGER PRIMARY KEY, name TEXT); > .explain > EXPLAIN > SELECT * > FROM employee, company, location > WHERE location.name=company.name > AND location.name=employee.name; > > Be sure to indent your code clearly so that people and understand it more > easily. > > For the trunk of SQLite, the first few instructions are: > > addr opcode p1 p2 p3 p4 p5 comment > ---- ------------- ---- ---- ---- ------------- -- ------------- > 0 Init 0 44 0 00 Start at 44 > 1 OpenRead 0 2 0 2 00 root=2 iDb=0; > employee > 2 OpenRead 2 3 0 2 00 root=3 iDb=0; > location > 3 OpenRead 1 4 0 2 00 root=4 iDb=0; > company > 4 Explain 0 0 0 SCAN TABLE employee > 00 > 5 Rewind 0 42 0 00 > 6 Once 0 14 0 00 > 7 OpenAutoindex 3 2 0 k(2,nil,nil) 00 nColumn=2; for > location > 8 Rewind 2 14 0 00 > 9 Column 2 1 2 00 r[2]= > location.name > 10 Rowid 2 3 0 00 r[3]=rowid > 11 MakeRecord 2 2 1 00 > r[1]=mkrec(r[2..3]) > 12 IdxInsert 3 1 0 10 key=r[1] > 13 Next 2 9 0 03 > > I think you are interested in knowing where the P3 operand (the output > register number) for instruction 9 comes from. (Note that the program > shown above might be slightly different in whatever version of SQLite you > are running.) > > The way you find this out is to first compile sqlite3 using > -DSQLITE_DEBUG. Then add the statement: > > PRAGMA vdbe_addoptrace=ON; > > Right before the "EXPLAIN" in the script. That pragma (only available when > SQLite is compiled with -DSQLITE_DEBUG) causes SQLite to print a message on > the screen every time it generates a new opcode. Next, run sqlite3 in a > debugger and set a breakpoint on the "test_addop_breakpoint" procedure. > (This is a dummy procedure created specifically to give you a place to set > a breakpoint.) Then run your script. Continue past the first few > breakpoints until the "Column" instruction is emitted. Now you can examine > the call stack to figure out exactly how that opcode was generated. > > It appears that the output register 2 comes from here: > > http://www.sqlite.org/src/artifact/fae81cc2eb14b?ln=812-813 > > Specifically the last parameter. regBase+j. You can continue to follow > the stack to figure out where regBase was computed. There are comments on > each function that try to explain what that particular function is doing. > > > > > > > -- > D. Richard Hipp > d...@sqlite.org > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
