OpenEuphoria

eds tables

• Posted by rudy toews <rltoews at ilos.net> May 30, 2002
• 464 views

hi all,
i have been trying to work on a table cross-reference addon for the eds 
database.e.  i am using version .5.
stress.ex will have problems with my code, but createdb and addone work 
ok. the database looks like it should.
i am trying to use a table in the current database to hold references to 
the other tables. whenever a record gets deleted or a table gets 
deleted, the pointers in database.e get corrupted and the wrong table is 
pointed to. this will cause the reference table to start collecting data 
meant for other tables. 
i believe the way garbage collection is done causes this to happen.
i have tried to select the current table again but it does not help.

some of the code is below:
-- Euphoria Database System table crossreference extension
include xrefdatabase.e  --the orignal file, 99.9% unchanged
sequence 
xrefprefix,xrefkey,xrefcurrenttable,xrefcurrentdb,xrefname,realname
integer tblxrefkeynum
object theretcode,xrefretcode

constant TBLXREF = "XREFTBL"
constant SCREEN = 1
xrefprefix = "xref"
global procedure db_dump(integer fn, integer low_level_too)
    xrefdb_dump(fn,low_level_too)
    return
end procedure

global function db_create(sequence path, integer lock_method)
-- when creating a new database, create the tblxref at the same time
-- tblxref will be the current table then! but keep it invisible
theretcode = xrefdb_create(path,lock_method)
if theretcode = DB_OK then
    xrefcurrentdb = path
    xrefretcode = xrefdb_create_table(TBLXREF)
    if xrefretcode != DB_OK then
		puts(SCREEN, "xreftbl not created \n")
    else
	xrefcurrenttable = ""
    end if
end if
return theretcode
end function

global function db_open(sequence path, integer lock_method)
--when opening a database, select the xreftbl table as 'default
theretcode = xrefdb_open(path,lock_method)
if theretcode = DB_OK then
    xrefcurrentdb = path
    xrefretcode = xrefdb_select_table(TBLXREF)
    if xrefretcode != DB_OK then
	puts(SCREEN,"dbopen creating the xreftbl\n")
    --if database is old then create the tblxref here
    -- future: collect the current table names , put into xref table
	xrefretcode = xrefdb_create_table(TBLXREF)
    if xrefretcode != DB_OK then
	puts(SCREEN,"dbopen cannot create the xreftbl table \n")
    end if
    end if
end if
xrefcurrenttable = ""
return theretcode
end function

global function db_select(sequence path)
theretcode = xrefdb_select(path)
if theretcode = DB_OK then
    xrefcurrentdb = path
    xrefretcode = xrefdb_select_table(TBLXREF)
    if xrefretcode != DB_OK then
	puts(SCREEN,"dbselect cannot select xreftbl\n")
    else
    xrefcurrenttable = ""
    end if
end if
return  theretcode
end function


global procedure db_close()
--put some code here to 'log the tblxref for backup purposes
--xrefretcode = xrefdb_select_table("TBLXREF")
--if xrefretcode != DB_OK then
    --printf(SCREEN,"%s","cannot close the tblxref")
--end if
--xrefcurrentdb = ""

xrefdb_close()
end procedure


global function db_create_table(sequence name)
--put code here to search the tblxref for the name with /without prefix
--if it does not exist in the table, maybe the database (old file)
--if not found then the create can make the table entry
--do the tblxref entry first, then the database entry so that the 
database
--entry is the last table pointed to when returning from this function.
xrefkey = xrefprefix & name
realname = name
--does the name already exist in the xref table
    xrefretcode = xrefdb_select_table(TBLXREF)
    if xrefretcode != DB_OK then
	puts(SCREEN,"dbcreate table cannot access the xreftbl \n")
    end if
    tblxrefkeynum = xrefdb_find_key(name)
    if tblxrefkeynum > 0 then
	puts(SCREEN,name & " already does exist  \n")
    else
	end if
    if tblxrefkeynum < 0 then
	xrefretcode = xrefdb_insert(name,xrefkey)
	puts(SCREEN,"putting the table into the xreftbl \n")
	if xrefretcode != DB_OK then
	    puts(SCREEN, xrefkey & " entry in xreftbl cannot be done \n")
	else
	    theretcode = xrefdb_create_table(xrefkey)
	if theretcode != DB_OK then
	    puts(SCREEN,"xreftable has entry but actual table not created\n")
	    tblxrefkeynum = tblxrefkeynum * -1
	    xrefdb_delete_record(tblxrefkeynum)
	end if
	end if
	
    end if
	
    if theretcode = DB_OK then
	xrefcurrenttable = name
    end if
return theretcode

end function


global function db_select_table(sequence name)
--look into the tblxref first,
--if the last thing done is with the realname then pointers will be 
correct
xrefname = xrefprefix & name
--xrefretcode = xrefdb_select_table(xrefname)
--if xrefretcode != DB_OK then
    xrefretcode = xrefdb_select_table(TBLXREF)
    if xrefretcode != DB_OK then
	puts(SCREEN,"dbselecttable unable to access xreftbl \n")
    else
	tblxrefkeynum = xrefdb_find_key(name)
	if tblxrefkeynum < 0 then
	    puts(SCREEN,name & " cannot be found in the xreftbl \n")
	else
	realname = xrefdb_record_data(tblxrefkeynum)
	xrefretcode = xrefdb_select_table(realname)
	puts(SCREEN,realname & " table is now selected " & xrefretcode & "\n")
	puts(SCREEN,name & "\n")
	--abort(1)
	end if
	
    end if
--else
--end if
theretcode = xrefretcode
if theretcode = DB_OK then
    xrefcurrenttable = name
else
puts(SCREEN,"no change in the current table selected \n")
end if
return theretcode
end function

global procedure db_delete_table(sequence name)
xrefname = xrefprefix & name
    puts(SCREEN,name & "and" & xrefcurrenttable & "\n")
    xrefretcode = xrefdb_select_table(TBLXREF)
    if xrefretcode != DB_OK then
	puts(SCREEN,"dbdeletetable unable to access xreftbl \n")
    else
	tblxrefkeynum = xrefdb_find_key(name)
	printf(SCREEN,"%d", tblxrefkeynum)
	if tblxrefkeynum < 0 then
		puts(SCREEN,"dbdeletetable cannot locate " & name &" \n")
	    
	    else

		puts(SCREEN,"the key to delete " & tblxrefkeynum & "\n")
		realname = xrefdb_record_data(tblxrefkeynum)
		xrefdb_delete_table(realname)
		xrefdb_delete_record(tblxrefkeynum)
		puts(SCREEN,"deleting tablexref entry - xrefname" & realname & "\n")
	end if

    end if
xrefretcode = db_select_table(xrefcurrenttable)
if xrefretcode != DB_OK then
    puts(SCREEN,"after dbtable delete, cannot return to old table \n")
end if
end procedure


global function db_table_list()
sequence onetable,alltables
integer totaltables
alltables =""
xrefretcode = xrefdb_select_table(TBLXREF)
if xrefretcode != DB_OK then
    puts(SCREEN,"table list error in selecting XREFTABLE \n")
    else
	totaltables = xrefdb_table_size()
	for i = 1 to totaltables by 1  do
	    onetable = xrefdb_record_key(i)
	    alltables = append(alltables,onetable)
	--puts(SCREEN,onetable & "\n")
	end for
--for i = 1 to length(alltables) by 1 do
    --puts(SCREEN,alltables[i] & "\n")
--end for
	--totaltables = length(alltables)
	--printf(SCREEN,"%10d",totaltables )
	--puts(SCREEN,"\n")
end if
--if getc(0) then
    
--end if
-- maybe find the entry for tblxref and delete it, huh..keep it 
invisible
xrefretcode = db_select_table(xrefcurrenttable)
--theretcode = xrefdb_table_list()
theretcode = alltables
--for i = 1 to length(theretcode) by 1 do
    --puts(SCREEN,theretcode[i] & "\n")
--end for
return theretcode
end function

global function db_compress()
--after a compression of the database , the pointers are updated
--so using tablenumbers would be out of the question!
theretcode = xrefdb_compress()
return theretcode
end function

the other functions have no alterations, are coded like db_compress.
this is a wrapper project, so the orginal database.e function names have 
been changed (including the spots where they are used in the non-public 
functions). this would allow apps to run without change.
and database.e logic go unchanged.

rudy
rltoews at ilos.net

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