PROJECT NAME: dbms3.r (temporary)
PURPOSE:
writing a small and simple relational database management system
in REBOL, for use with applications that don't need a full blown
separate DBMS such as MySQL. With respect to dbms.r, it will be
more efficient in the data storage to be usable with much more
rows per table, and possibly will have a more powerful/abstracted
interface.
DEVELOPMENT, part 2
here i am again... didn't expect to cause all that traffic. i'll
go off-list soon.
first, let me make a correction to the low level interface:
--
memory-table-funcs: context [
; memory-table-funcs-code
row-append: func [
"Append a row to an on-memory table"
table [object!]
row [block!]
; returns the row-id of the new row
] row-append-code
row-pick: func [
"Pick a row from an on-memory table"
table [object!]
row-id [integer!]
; returns the row or none! for an invalid row-id
] row-pick-code
row-change: func [
"Change a row in an on-memory table"
table [object!]
row-id [integer!]
new-row [block!]
; returns the row-id of the changed row, or none! for
; an invalid row-id
] row-change-code
row-remove: func [
"Remove a row from an on-memory table"
table [object!]
row-id [integer!]
; returns true, or false if the row-id is invalid
] row-remove-code
]
--
you see i changed object! to block! for rows; object!s should be
handled at a higher level than this. i also changed the argument
name for row-change so that it is clearer that it needs a complete
new row now.
now we can start with the code; we'll need to know how an in
memory table object! looks like. at this time we just need:
--
create-memory-table: func [
"Create a new on-memory table"
; returns the new table object!
] [
context [
data: make block! 1024
]
]
--
so...
--
row-append: func [
"Append a row to an on-memory table"
table [object!]
row [block!]
; returns the row-id of the new row
] [
; row-append-code
insert/only tail table/data row
length? table/data
]
--
wrt the discussions on the list, the row-id is the position in the
block, so it is implicitly present; the status we are interested
with in this case can only be "present" or "deleted": so it is
present when the element in the data block is a block and is
deleted when it is none. this way row-pick will magically work as:
--
row-pick: func [
"Pick a row from an on-memory table"
table [object!]
row-id [integer!]
; returns the row or none! for an invalid row-id
] [
; row-pick-code
pick table/data row-id
]
--
for in-memory tables the row-id does not need to change upon
record changes, and row-change will be as simple as:
--
row-change: func [
"Change a row in an on-memory table"
table [object!]
row-id [integer!]
new-row [block!]
; returns the row-id of the changed row, or none! for
; an invalid row-id
] [
; row-change-code
poke table/data row-id new-row
row-id
]
--
well, actually it needs some error checking. row-id should not be
greater than length? table/data and should not refer to a deleted
record. if this happens, none! should be returned. pick handles
both the cases well.
--
row-change: func [
"Change a row in an on-memory table"
table [object!]
row-id [integer!]
new-row [block!]
; returns the row-id of the changed row, or none! for
; an invalid row-id
] [
; row-change-code
if not found? pick table/data row-id [
return none
]
poke table/data row-id new-row
row-id
]
--
as last:
--
row-remove: func [
"Remove a row from an on-memory table"
table [object!]
row-id [integer!]
; returns true, or false if the row-id is invalid
] [
either found? pick table/data row-id [
poke table/data row-id none
true
] [
false
]
]
--
time for a bit of testing, heh? i'm using test code such as:
--
test-code: func [code] [
print [
"Call: " trim/lines mold code newline
"Result:" newline mold do code
]
]
random/seed now
print "On Memory low-level functions test"
print "*********************************************"
print "Creating table"
test-code [
test-table: create-memory-table
]
print "*********************************************"
print "Simple test"
test-code [row-append test-table [1 2 3]]
test-code [row-pick test-table 1]
test-code [row-change test-table 1 [4 5 6]]
test-code [row-pick test-table 1]
test-code [row-remove test-table 1]
test-code [row-pick test-table 1]
test-code [row-change test-table 1 [7 8 9]]
test-code [row-pick test-table 1]
print "*********************************************"
print "RANDOM test"
print "*********************************************"
print ["Testing row-append for" n: random 1024 "runs"]
loop n [
test-code compose/deep [
row-append test-table [
(random 10) (random 10) (random 10)
]
]
]
print "*********************************************"
print ["Testing row-pick for" n: random 100 "runs"]
loop n [
test-code compose [row-pick test-table (random 1024)]
]
print "*********************************************"
print ["Testing row-change for" n: random 100 "runs"]
loop n [
test-code compose/deep [
row-change test-table (random 1024) [
(random 10) (random 10) (random 10)
]
]
]
print "*********************************************"
print ["Testing row-pick for" n: random 100 "runs"]
loop n [
test-code compose [row-pick test-table (random 1024)]
]
print "*********************************************"
print ["Testing row-remove for" n: random 100 "runs"]
loop n [
test-code compose [row-remove test-table (random 1024)]
]
print "*********************************************"
print ["Testing row-change for" n: random 100 "runs"]
loop n [
test-code compose/deep [
row-change test-table (random 1024) [
(random 10) (random 10) (random 10)
]
]
]
print "*********************************************"
print ["Testing row-pick for" n: random 100 "runs"]
loop n [
test-code compose [row-pick test-table (random 1024)]
]
print "On Memory low-level functions test - END"
print "*********************************************"
--
which seems to produce reasonable output.
[TO BE CONTINUED]
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