How do I store an unsigned int (uint32) in postgres? I noticed that numeric(10,0) would fit the number of digits, but is this the best way?
On further research another similar problem is storing a uint64. I've found numeric(20,0) check (BETWEEN 0 AND '18446744073709551615'::numeric(20,0)). There aren't any native types for this I believe.
Arithmetic on numeric values is very slow compared to the integer types.
Use bigint. It stores an 8 byte integer up to 2^63 - 1 = 9223372036854775807
[You probably don't need the entire unsigned range]
Related
There is an existing question about why there is no unsigned integer (32 bit) and the answer was because it is not an SQL standard and the solution was using domain. Basically the answer was using a 32-bit signed integer and restricting it to a 16-bit unsigned integer range.
But what if I want an unsigned long integer (64 bit)? There do not seem to exist int9 or int16.
create domain uint8 as int16 check(value>=0 and value<18446744073709551615)
ERROR: type "int16" does not exist SQL state: 42704
I am trying to map the java type to the SQL type and I encountered such a scenario.
If I elaborate, I was using the auto-ddl api to apply scripts to my database while starting my spring container. Now I am trying to generate the scripts using liquibase by generating the db-changelog for POSTGRE server.
Are numeric(19,0) and BIGINT same in Postgres server? Please put some light on this.
The main difference is the storage:
bigint (and smallint and integer) are stored as integer values in the processor's native format (usually two's complement binary numbers).
The range is limited (but high), the storage space occupied is 8 bytes, and arithmetic is blazingly fast.
numeric is stored as binary coded decimal of variable length.
The range and the precision is almost unlimited (up to 131072 digits before the decimal point; up to 16383 digits after the decimal point), but arithmetic operations are comparatively slow.
BIGINT range is -9223372036854775808 to 9223372036854775807, so you can't store a number greater than 9223372036854775807, but NUMERIC (19, 0) can do.
Please find the following example:
CREATE TABLE TestTable (NumVal NUMERIC (19,0), IntVal BIGINT);
INSERT INTO TestTable (NumVal, IntVal) VALUES
('9223372036854775808', 9223372036854775807);
SELECT * FROM TestTable;
Here you can't store 9223372036854775808 in to BIGINT, but you can store the same value or greater than the value to NUMERIC (19, 0)
db<>fiddle for the same.
Numeric has variable storage size, while bigint is always 8 bytes.
SELECT pg_column_size(123456789112345678911111555678::numeric(30,0)) AS numeric30,
pg_column_size(1234567891123456789::numeric(19,0)) AS numeric19,
pg_column_size(123::numeric(19,0)) AS numeric3,
pg_column_size(1234567891123456789::bigint) AS bigint;
numeric30|numeric19|numeric3|bigint
---------|---------|--------|------
22| 16| 8| 8
Additionaly, from documentation (emphasis mine):
Calculations with numeric values yield exact results where possible,
e.g. addition, subtraction, multiplication. However, calculations on
numeric values are very slow compared to the integer types, or to the
floating-point types described in the next section.
I was looking for a way to create a table with unsigned integer (I know I will have only positive integers, so why not to increase the range twofold). To create an integer field, I do:
create table funny_table(
my_field bigint
);
So I thought that using my_field bigint unsigned will solve my problem, but syntax error tells me otherwise. Looking though the documentation tells nothing about unsigned integers. Is it even possible?
Unfortunately Amazon Redshift doesn't support unsigned integer. As a workaround, we are using numeric(20,0) for bigint unsigned data. Here is an example.
create table funny_table(
my_field numeric(20, 0)
);
insert into funny_table values ( 18446744073709551614 );
select * from funny_table;
my_field
----------------------
18446744073709551614
(1 row)
See here for the details of Numeric type.
As already mentioned, Redshift does not support unsigned. Given that, please take a closer at what you need to achieve.
bigint occupies 8 bytes giving you a range of -9223372036854775808 to 9223372036854775807
numeric occupies 128-bit (Variable, up to 128 bits) but offers a bigger range at the expense of memory.
I believe the idea behind using unsigned is doubling the range WITHOUT EXTRA EXPENSE TO STORAGE. So if you are comfortable with the highest positive value of 2^63 - 1 go with bigint and forget about the unsigned because it costs 8 bytes anyway.
If you have bigger positive integers go with numeric(20, 0) (or higher precision) but you need to be aware that it is still signed and occupies more than 8 bytes.
For anyone that is running into the issue that they cant copy the unsigned int value from the source table:
You have to change the tupple mapping from previously:
("id", "int", "id", "int")
to
("id", "id", "decimal(20,0)")
We always had null values in our redshift cluster for the id. The change in the mapping changed this behaviour, which resulted in correctly copying the value from the source table.
Bigint in postgresql is 8 byte integer. which is has half the range as uint64 (as one bit is used to sign the integer)
I need to do a lot of aggregation on the column and I am under the impression that aggregation on NUMERIC type is slow in comparison to integer types.
How should I optimize my storage in this case?
Unless you have a concrete reason, just use NUMERIC. It is slower, quite a lot slower, but that might not matter as much as you think.
You don't really have any alternative, as PostgreSQL doesn't support unsigned 64-bit integers at the SQL level. You could add a new datatype as an extension module, but it'd be a lot of work.
You could shove the unsigned 64-bit int bitwise into a 64-bit signed int, so values above maxuint64/2 are negative. But that'll be totally broken for aggregation, and would generally be horribly ugly.
sum() will return numeric if the input is bigint so it will not overflow
select sum(a)
from (values (9223372036854775807::bigint), (9223372036854775807)) s(a)
;
sum
----------------------
18446744073709551614
http://www.postgresql.org/docs/current/static/functions-aggregate.html
There is also an extension to provide an additional uint64 datatype in postgresql. See Github
It is by Peter Eisentraut
I came across this post (What is the difference between tinyint, smallint, mediumint, bigint and int in MySQL?) and realized that PostgreSQL does not support unsigned integer.
Can anyone help to explain why is it so?
Most of the time, I use unsigned integer as auto incremented primary key in MySQL. In such design, how can I overcome this when I port my database from MySQL to PostgreSQL?
Thanks.
It's not in the SQL standard, so the general urge to implement it is lower.
Having too many different integer types makes the type resolution system more fragile, so there is some resistance to adding more types into the mix.
That said, there is no reason why it couldn't be done. It's just a lot of work.
It is already answered why postgresql lacks unsigned types. However I would suggest to use domains for unsigned types.
http://www.postgresql.org/docs/9.4/static/sql-createdomain.html
CREATE DOMAIN name [ AS ] data_type
[ COLLATE collation ]
[ DEFAULT expression ]
[ constraint [ ... ] ]
where constraint is:
[ CONSTRAINT constraint_name ]
{ NOT NULL | NULL | CHECK (expression) }
Domain is like a type but with an additional constraint.
For an concrete example you could use
CREATE DOMAIN uint2 AS int4
CHECK(VALUE >= 0 AND VALUE < 65536);
Here is what psql gives when I try to abuse the type.
DS1=# select (346346 :: uint2);
ERROR: value for domain uint2 violates check constraint "uint2_check"
You can use a CHECK constraint, e.g.:
CREATE TABLE products (
id integer,
name text,
price numeric CHECK (price > 0)
);
Also, PostgreSQL has serial, smallserial and bigserial types for auto-increment.
The talk about DOMAINS is interesting but not relevant to the only possible origin of that question. The desire for unsigned ints is to double the range of ints with the same number of bits, it's an efficiency argument, not the desire to exclude negative numbers, everybody knows how to add a check constraint.
When asked by someone about it, Tome Lane stated:
Basically, there is zero chance this will happen unless you can find
a way of fitting them into the numeric promotion hierarchy that doesn't
break a lot of existing applications. We have looked at this more than
once, if memory serves, and failed to come up with a workable design
that didn't seem to violate the POLA.
What is the "POLA"? Google gave me 10 results that are meaningless. Not sure if it's politically incorrect thought and therefore censored. Why would this search term not yield any result? Whatever.
You can implement unsigned ints as extension types without too much trouble. If you do it with C-functions, then there will be about no performance penalties at all. You won't need to extend the parser to deal with literals because PgSQL has such an easy way to interpret strings as literals, just write '4294966272'::uint4 as your literals. Casts shouldn't be a huge deal either. You don't even need to do range exceptions, you can just treat the semantics of '4294966273'::uint4::int as -1024. Or you can throw an error.
If I wanted this, I would have done it. But since I'm using Java on the other side of SQL, to me it is of little value since Java doesn't have those unsigned integers either. So I gain nothing. I'm already annoyed if I get a BigInteger from a bigint column, when it should fit into long.
Another thing, if I did have the need to store 32 bit or 64 bit types, I can use PostgreSQL int4 or int8 respectively, just remembering that the natural order or arithmetic won't work reliably. But storing and retrieving is unaffected by that.
Here is how I can implement a simple unsigned int8:
First I will use
CREATE TYPE name (
INPUT = uint8_in,
OUTPUT = uint8_out
[, RECEIVE = uint8_receive ]
[, SEND = uint8_send ]
[, ANALYZE = uint8_analyze ]
, INTERNALLENGTH = 8
, PASSEDBYVALUE ]
, ALIGNMENT = 8
, STORAGE = plain
, CATEGORY = N
, PREFERRED = false
, DEFAULT = null
)
the minimal 2 functions uint8_in and uint8_out I must first define.
CREATE FUNCTION uint8_in(cstring)
RETURNS uint8
AS 'uint8_funcs'
LANGUAGE C IMMUTABLE STRICT;
CREATE FUNCTION uint64_out(complex)
RETURNS cstring
AS 'uint8_funcs'
LANGUAGE C IMMUTABLE STRICT;
need to implement this in C uint8_funcs.c. So I go use the complex example from here and make it simple:
PG_FUNCTION_INFO_V1(complex_in);
Datum complex_in(PG_FUNCTION_ARGS) {
char *str = PG_GETARG_CSTRING(0);
uint64_t result;
if(sscanf(str, "%llx" , &result) != 1)
ereport(ERROR,
(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
errmsg("invalid input syntax for uint8: \"%s\"", str)));
return (Datum)SET_8_BYTES(result);
}
ah well, or you can just find it done already.
According to the latest documentation, the signed integer is supported but no unsigned integer in the table. However, the serial type is kind of similar to unsigned except it starts from 1 not from zero. But the upper limit is the same as signed. So the system truly does not have unsigned support. As pointed out by Peter, the door is open to implement the unsigned version. The code may have to be updated a lot, just too much work from my experience working with C programming.
https://www.postgresql.org/docs/10/datatype-numeric.html
integer 4 bytes typical choice for integer -2147483648 to +2147483647
serial 4 bytes autoincrementing integer 1 to 2147483647
Postgres does have an unsigned integer type that is unbeknownst to many: OID.
The oid type is currently implemented as an unsigned four-byte integer. […]
The oid type itself has few operations beyond comparison. It can be
cast to integer, however, and then manipulated using the standard
integer operators. (Beware of possible signed-versus-unsigned confusion
if you do this.)
It is not a numeric type though, and trying to do any arithmetic (or even bitwise operations) with it is going to fail. Also, it's just 4 bytes (INTEGER), there is no corresponding 8 byte (BIGINT) unsigned type.
So it's not really a good idea to use this yourself, and I agree with all the other answers that in a Postgresql database design you should always use an INTEGER or BIGINT column for your serial primary key - having it start in the negative (MINVALUE) or allowing it to wrap around (CYCLE) if you want to exhaust the full domain.
However, it is quite useful for input/output conversion, like your migration from another DBMS. Inserting the value 2147483648 into an integer column will lead to an "ERROR: integer out of range", while using the expression 2147483648::OID works just fine.
Similarly, when selecting an integer column as text with mycolumn::TEXT, you will get negative values at some point, but with mycolumn::OID::TEXT you will always get a natural number.
See an example at dbfiddle.uk.