id.602271.mils

一个内存数据库的源代码这是服务器端还有客户端

# Date:		2002-08-30 00:57
# Priority:	5
# Submitted By:	Alex van Ballegooij (bally)
# Assigned To:	Niels Nes (nielsnes)
# Category:	None
# Status:	Closed
# Summary:
# oid v.s. void bat behavior
# 
# void bats behave differntly fomr oid bats under insertion, 
# yet it is possible to unexpectedly end up with void 
# bats after certain operations (e.g. join), which could 
# lead to unpredictable behavior. 

# Build two simple bats, using OIDs.
var oid_oid_bat := insert(insert(bat(oid,oid),oid(0),oid(0)),oid(1),oid(1));
print(oid_oid_bat);

var oid_int_bat := insert(insert(bat(oid,int),oid(0),0),oid(1),1);
print(oid_int_bat);

# Monet decides to make the join result VOID (which is possible),
# what makes this problematic however is the difference in behavior in
# the subsequent insert-tests.
var void_int_bat := join(oid_oid_bat,oid_int_bat);
print(void_int_bat);

# inserting 'in-sequence' into an OID bat
# a single (OID) tuple 
print(insert(access(copy(oid_int_bat),BAT_WRITE),
      oid(2),2));
# a complete (OID) bat.
print(insert(access(copy(oid_int_bat),BAT_WRITE),
      insert(bat(oid,int),oid(2),2)));
# a complete (VOID) bat.
print(insert(access(copy(oid_int_bat),BAT_WRITE),
             insert(seqbase(bat(void,int),oid(2)),oid(2),2)));

# inserting 'out-of-sequence' into an OID bat
# a single (OID) tuple 
print(insert(access(copy(oid_int_bat),BAT_WRITE),
      oid(10),10));
# a complete (OID) bat.
print(insert(access(copy(oid_int_bat),BAT_WRITE),
      insert(bat(oid,int),oid(10),10)));
# a complete (VOID) bat.
print(insert(access(copy(oid_int_bat),BAT_WRITE),
             insert(seqbase(bat(void,int),oid(10)),oid(10),10)));

# inserting 'in-sequence' into a VOID bat
# a single (OID) tuple 
print(insert(access(copy(void_int_bat),BAT_WRITE),
      oid(2),2));
# a complete (OID) bat.
print(insert(access(copy(void_int_bat),BAT_WRITE),
      insert(bat(oid,int),oid(2),2)));
# a complete (VOID) bat.
print(insert(access(copy(void_int_bat),BAT_WRITE),
             insert(seqbase(bat(void,int),oid(2)),oid(2),2)));

# inserting 'out-of-sequence' into a VOID bat
# a single (OID) tuple 
# This test gives an error:
print(insert(access(copy(void_int_bat),BAT_WRITE),
      oid(10),10));
# These two tests give incorrect answers:
# a complete (OID) bat.
print(insert(access(copy(void_int_bat),BAT_WRITE),
      insert(bat(oid,int),oid(10),10)));
# a complete (VOID) bat.
print(insert(access(copy(void_int_bat),BAT_WRITE),
             insert(seqbase(bat(void,int),oid(10)),oid(10),10)));

#
# The void-bats behave strange under insertion,
# Either errors should be given consequently 
# (as soon as a tuple 'out-of-sequence' is inserted)
# or void bats should be materialized to oid when needed.
#
# I would argue for the latter, as there is no real reason 
# for a user to expect the bat in this example to be void,
# (a join result of a [oid,oid] and a [oid,int] bat), yet
# it behaves differently from what a user would expect from
# the (expected) [oid,int] bat.
#
# The provided stable output has been hand-crafted to 
# depict that which I argue to be the 'correct' outpu.
#