COMP9315 21T1 – Assignment 1
COMP9315 21T1
Assignment 1
Adding a Set Data Type to PostgreSQL
DBMS Implementation
Last updated: Wednesday 3rd March 1:01pm
Most recent changes are shown in red;
older changes are shown in brown.
This is a working draft.
Small updates and clarifications will be added as needed.
No major changes are anticipated.
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summary
introduction
setup
intsets
(
values
operations
representing
)
changelog
submission
Summary
Deadline
Friday 19 March, 9:00pm
Marks
This assignment contributes 15 marks toward your total mark for this course.
Late Penalty
0.089 marks off the ceiling mark for each hour late.
After 7 days the assignment is worth 0 marks.
Submission
From WebCMS:
COMP9315 website,
->
Assignments,
->
Ass1 Specification,
->
Make Submission,
->
upload intset.c, intset.source, [
or
From CSE:
give cs9315 ass1 intset.c intset.source [
Pre-requisites
Before starting this assignment, it would be useful to complete Prac Exercise P04.
This assignment aims to give you:
An understanding of how data is treated inside a DBMS
Practice in adding a new base type to PostgreSQL
The goal is to implement a new data type for PostgreSQL,
complete with input/output functions and a range of operations.
Make sure that you read this assignment specification
carefully and completely
before starting work on the assignment.
Questions which indicate that you haven’t done this
will simply get the response “Please read the spec”.
We will be using the following names in the discussion below:
PG_CODE
The directory where your PostgreSQL source code is located
(typically /srvr/$USER/postgresql-12.5)
PG_HOME
The directory where you have installed the PostgreSQL binaries
(typically /srvr/$USER/pgsql)
PG_DATA
The directory where you have placed PostgreSQL’s data
(typically /srvr/$USER/pgsql/data)
PG_LOG
the file to where you send PostgreSQL’s log output
(typically /srvr/$USER/pgsql/log)
Introduction
PostgreSQL has an extensibility model which, among other things,
provides a well-defined process for adding new data types into a PostgreSQL server.
This capability has led to the development by PostgreSQL users of a number of types (such as polygons)
which have become part of the standard distribution.
It also means that PostgreSQL is the database of choice in research projects which aim to
push the boundaries of what kind of data a DBMS can manage.
In this assignment, we will be adding a new data type for dealing with sets of integers.
You may implement the functions for the data type in any way you like,
provided that they satisfy the semantics given below.
(in the intSets section)
Note that arrays in PostgreSQL have some properties and operations that make them look a little bit like sets.
However, they are not sets and have quite different semantics to the data type that we are asking you to implement.
The process for adding new base data types in PostgreSQL is described in the following sections of the PostgreSQL documentation:
37.10 C-Language Functions
37.13 User-defined Types
37.14 User-defined Operators
SQL: CREATE TYPE
SQL: CREATE OPERATOR
SQL: CREATE OPERATOR CLASS
Section 37.13 uses an example of a complex number type,
which you can use as a starting point for defining your intSet data type (see below).
Note that the complex type is a starting point only, to give an idea
on how new data types are added.
Don’t be fooled into thinking that this assignment just requires you
to change the name complex to intSet; the intSet
type is more complex (no pun intended) than the complex number type.
There are other examples of new data types under the tutorial and
contrib directories.
These may or may not give you some useful ideas on how to implement
the intSet data type:
An auto-encrypted password datatype
PG_CODE/contrib/chkpass/
A case-insensitive character string datatype
PG_CODE/contrib/citext/
A confidence-interval datatype
PG_CODE/contrib/seg/
Setting Up
You ought to start this assignment with a fresh copy of PostgreSQL,
without any changes that you might have made for the Prac exercises
(unless these changes are trivial).
Note that you only need to configure, compile, and install your PostgreSQL server once for this assignment.
All subsequent compilation takes place in the src/tutorial directory,
and only requires modification of the files there.
Once you have re-installed your PostgreSQL server, you should run the following commands:
cd PG_CODE/src/tutorial
cp complex.c intset.c
cp complex.source intset.source
Once you’ve made the intset files,
you should also edit the Makefile in this directory,
and add the green text
to the following lines:
MODULES = complex funcs intset
DATA_built = advanced.sql basics.sql complex.sql funcs.sql syscat.sql intset.sql
The rest of the work for this assignment involves editing
the intset.c and intset.source files.
In order for the Makefile to work properly,
you must use the identifier _OBJWD_
in the intset.source file
to refer to the directory holding the compiled library.
You should never directly modify the intset.sql file
produced by the Makefile.
If you want to use other *.c files
along with intset.c, then you can do so,
but you will need to make further changes to the Makefile
to ensure that they are compiled and linked correctly into the library.
Note that your submitted versions of
intset.c and intset.source
should not contain any references to the complex type
(because that’s not what you’re implementing).
Make sure that the comments in the program describes the code that you wrote.
Also, do not put testing queries in your intset.source;
all it should do is create the new data type.
Put any testing you want to do in a separate *.sql, which
you don’t need to submit.
And do not drop the intSet type at the end of
intset.source. If you do, your data type will vanish before
we have a chance to test it.
The intSet Data Type
We aim to define a new base type intSet, to store the notion of sets of integer values.
We also aim to define a useful collection of operations on the intSet type.
How you represent intSet values,
and implement functions to manipulate them,
is up to you.
However, they must satisfy the requirements below
Once implemented correctly,
you should be able to use your PostgreSQL server
to build the following kind of SQL applications:
create table Features (
id integer primary key,
name text
);
create table DBSystems (
name text primary key,
features intSet
);
insert into Features (id, name) values
(1, ‘well designed’),
(2, ‘efficient’),
(3, ‘flexible’),
(4, ‘robust’);
insert into DBSystems (name, features) values
(‘MySQL’, ‘{}’),
(‘MongoDB’, ‘{}’),
(‘Oracle’, ‘{2,4}’),
(‘PostgreSQL’, ‘{1,2,3,4}’);
intSet values
In mathematics, we represent a set as a curly-bracketed, comma-separated collection of values:
{1,2,3,4,5}{1,2,3,4,5}
Such a set contains only distinct values, and no particular ordering can be imposed.
Our intSet values can be represented similarly.
We can have a comma-separated list of non-negative integers,
surrounded by a set of curly braces,
which is presented to and by PostgreSQL as a string.
For example:
‘{ 1, 2, 3, 4, 5 }’.
Whitespace should not matter,
so ‘{1,2,3}’ and
‘{ 1, 2, 3 }’ are equivalent.
Similarly, a set contains distinct values,
so ‘{1,1,1,1,1}’
is equivalent to ‘{1}’.
And ordering is irrelevant,
so ‘{1,2,3}’
is equivalent to ‘{3,2,1}’.
The integer values in the set are assumed to consist of
a sequence of digits. There are no + or – signs.
There can be leading zeroes, but they should effectively be ignored,
e.g. 0001 should be treated the same as 1.
You may not assume a fixed limit to the size of the set.
It may contain zero or more elements, bounded by the database’s capacity to store values.
You may assume that each interger value will be less than INT_MAX.
ie. each element in the set will be less than 231−1231−1.
Valid intSets
‘{ }’
‘{2,3,1}’
‘{6,6,6,6,6,6}’
‘{10, 9, 8, 7, 6,5,4,3,2,1}’
‘{1, 999, 13, 666, 5}’
‘{ 1 , 3 , 5 , 7,9 }’
‘{1, 01, 001, 0001}’ (same as ‘{1}’)
‘{1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20}’
‘{1,2,3,4,5,6,7,8,9,10,(and then all numbers to),9999,10000}’
‘ {1,5,7,9}’
‘{2,4,6, 8 } ‘
‘{0}’
Invalid intSets
‘{a,b,c}’
‘{ a, b, c }’
‘{1, 2.0, 3}’
‘{1, {2,3}, 4}’
‘{1, 2, 3, 4, five}’
‘{ 1 2 3 4 }’
‘1 2 3 4’
‘1 2 3}’
‘{ -1 }’
‘{1,2,3’
‘1,2,3,4,5’
‘{{1,2,3,5}’
‘{7,17,,27,37}’
‘{1,2,3,5,8,}’
Operations on intSets
You must implement all of the following operations for the intSet type.
(assuming AA, BB, and SS are intSets, and ii is an integer):
i ? S
intSet SS contains the integer ii;
That is, i∈Si∈S.
# S
Give the cardinality, or number of distinct elements in, intSet SS;
That is, |S||S|.
A >@ B
Does intSet AA contain all the values in intSet BB?
ie, for every element of BB, is it an element of AA?
That is, the improper superset (A⊇BA⊇B)
A @< B Does intSet AA contain only values in intSet BB? ie, for every element of AA, is it an element of BB? That is, the improper subset (A⊆BA⊆B) A = B intSets AA and BB are equal; That is, intSet AA contains all the values of intSet BB and intSet BB contains all the values of intSet AA; That is, every element in AA can be found in BB, and vice versa. A <> B
intSets AA and BB are not equal;
That is, intSet AA doesn’t contain all the values of intSet BB or intSet BB doesn’t contain all the values of intSet AA;
That is, some element in AA cannot be found in BB, or vice versa.
A && B
Takes the set intersection, and produces an intSet containing the elements common to AA and BB;
That is, A∩BA∩B.
A || B
Takes the set union, and produces an intSet containing all the elements of AA and BB;
That is, A∪BA∪B.
A !! B
Takes the set disjunction, and produces an intSet containing elements that are in AA and not in BB,
or that are in BB and not in AA.
A – B
Takes the set difference, and produces an intSet containing elements that are in AA and not in BB.
Note that this is not the same as A !! B.
Below are examples of how you might use intSets, to illustrate the semantics.
You can use these as an initial test set; we will supply a more comprehensive test suite later.
create table mySets (id integer primary key, iset intSet);
CREATE TABLE
insert into mySets values (1, ‘{1,2,3}’);
INSERT 0 1
insert into mySets values (2, ‘{1,3,1,3,1}’);
INSERT 0 1
insert into mySets values (3, ‘{3,4,5}’);
INSERT 0 1
insert into mySets values (4, ‘{4,5}’);
INSERT 0 1
select * from mySets order by id;
id | iset
—-+———
1 | {1,2,3}
2 | {1,3}
3 | {3,4,5}
4 | {4,5}
(4 rows)
— get all pairs of tuples where the second iset is a subset of first iset
select a.*, b.* from mySets a, mySets b
where (b.iset @< a.iset) and a.id != b.id;
id | iset | id | iset
----+---------+----+-------
1 | {1,2,3} | 2 | {1,3}
3 | {3,4,5} | 4 | {4,5}
(2 rows)
-- insert extra values into the iset in tuple #4 via union
update mySets set iset = iset || '{5,6,7,8}' where id = 4;
UPDATE 1
select * from mySets where id=4;
id | iset
----+-------------
4 | {4,5,6,7,8}
(1 row)
-- tuple #4 is no longer a subset of tuple #3
select a.*, b.* from mySets a, mySets b
where (b.iset @< a.iset) and a.id != b.id;
id | iset | id | iset
----+---------+----+-------
1 | {1,2,3} | 2 | {1,3}
(1 row)
-- get the cardinality (size) of each intSet
select id, iset, (#iset) as card from mySets order by id;
id | iset | card
----+-------------+------
1 | {1,2,3} | 3
2 | {1,3} | 2
3 | {3,4,5} | 3
4 | {4,5,6,7,8} | 5
(4 rows)
-- form the intersection of each pair of sets
select a.iset, b.iset, a.iset && b.iset
from mySets a, mySets b where a.id < b.id;
iset | iset | ?column?
---------+-------------+----------
{1,2,3} | {1,3} | {1,3}
{1,2,3} | {3,4,5} | {3}
{1,2,3} | {4,5,6,7,8} | {}
{1,3} | {3,4,5} | {3}
{1,3} | {4,5,6,7,8} | {}
{3,4,5} | {4,5,6,7,8} | {4,5}
(6 rows)
delete from mySets where iset @< '{1,2,3,4,5,6}';
DELETE 3
select * from mySets;
id | iset
----+-------------
4 | {4,5,6,7,8}
(1 row)
-- etc. etc. etc.
You should think of some more tests of your own.
In particular, make sure that you check that your code works with large intSets (e.g. cardinality ≥ 1000).
If you come up with any tests that you think are particularly clever, feel free to post them in the comments section below.
Representing intSets
The first thing you need to do is to decide on an internal representation for your intSet data type.
You should do this after you have understood the description of the operators above.
Since what they require may affect how you decide on the representation of your intSet values.
Note that because of the requirement that an intSet can be arbitrarily large (see above),
you cannot have a representation that uses a fixed-size object to hold values of type intSet.
When you read strings representing intSet values, they are converted into your internal form,
stored in the database in this form, and operations on intSet values are carried out using this data structure.
When you display intSet values,
you should show them in a canonical form,
regardless of how they were entered or how they are stored.
The canonical form for output (at least) should include no
spaces, and should have elements in ascending order.
The first functions you need to write
are ones to read and display values of type intSet.
You should write analogues of the functions
complex_in() and complex_out()
that are defined in the file complex.c.
Suitable names for these functions would be e.g.
intset_in() and intset_out().
Make sure that you use the V1 style function interface
(as is done in complex.c).
Note that the two input/output functions should be complementary,
meaning that any string displayed by the output function
must be able to be read using the input function.
There is no requirement for you to retain the precise string that was used for input
(e.g. you could store the intSet value internally in canonical form).
Note that you are not required
to define binary input/output functions called
receive_function and send_function
in the PostgreSQL documentation, and called
complex_send() and complex_recv()
in the complex.c file.
Hint:
test out as many of your C functions as you can
outside PostgreSQL
(e.g., write a simple test driver)
Before you try to install them in PostgreSQL.
This will make debugging much easier.
You should ensure that your definitions
capture the full semantics of the operators
(e.g. specify commutativity if the operator is commutative).
ChangeLog
v1.0
(2021-02-26 15:00:00+10:00)
released Assignment 1
v1.1
(2021-02-27 11:00:00+10:00)
Modify the "Operations on intSets" section
Change the symbol for "contains" from '<@' to '?'
Change the symbol for "cardinality" from '@' to '#'
Change the symbol for "subset" from '@>‘ to ‘@<'
Add the "superset" operation, using the '>@’ symbol
Add the “inequality” operation, using the ‘<>‘ symbol
v1.2
(2021-02-26 16:00:00+10:00)
Corrected typo in examples of Valid IntSets
Add addidtional examples of (In)Valid IntSets
Add an upper bound for the size of each element in an IntSet
v1.3
(2021-02-26 18:00:00+10:00)
Correct superset and subset symbles used in “Operations on intSets”
v1.4
(2021-03-01 18:00:00+10:00)
Moved deadline forward to 9pm to be consistent with CSE policy
Submission
You need to submit two files:
intset.c – containing the C functions
that implement the internals of the intSet data type.
intset.source – containing the template SQL commands
to install the intSet data type into a PostgreSQL server.
Do not submit the intset.sql file,
since it contains absolute file names which are not useful in our test environment.
If your system requires other *.c files, you should submit them,
along with the modified Makefile from the src/tutorial directory.
Do not include:
create table …
insert into …
select …
drop type …
Or any other statements not directly needed for creating
the intSet data type in intset.source.
Have fun, jas and dylan.