I'm trying to define a bit field of 10 bytes. In SQL Server I'd use varbinary(10). I know that bytea replaces varbinary (MAX) for images, but didn't find any documentation on limiting the number of bits in it.
Is there a way to do that?
you want to look at bit(n), not bytea
http://www.postgresql.org/docs/current/static/datatype-bit.html
Related
We had a table with a column with a Clob(length 1048576) that would store search text that helps with searching. When I transferred it from DB2 to Postgres in our migration, I found that it wasn't working as well. So I going to try text or varchar, but I was finding it would take much longer for the long text entries to be added to the table to the point my local wildfly window would timeout when trying to run.
What is the equilavelent of a datatpye that accepts text that I should be using in postgres to replace a Clob that was length 1048576 in DB2? It might be that I was using the right datatypes but didn't have the right corresponding size.
Use text. That is the only reasonable data type for long character strings.
Currently I'm using serial datatype for my project. I want to know the following details to change previously Created SEQUENCE datatype to SERAIL datatype.
From Which version onwards POSTGRESQL supports SERAIL DATATYPE, also If I change my id into SERAIL it wont affect my future code.
What is the max size of serial and its impact?
Can ALTER SEQUENCE impact the Sequence numbers?
any drawback on serail datatype in future?
How to create gap-less sequence?
All answers can be found in the manual
serial goes back to Postgres 7.2
It's a bigint, the max size is documented in the manual. Also see this note in the documenation of CREATE SEQUENCE
Sequences are based on bigint arithmetic, so the range cannot exceed the range of an eight-byte integer (-9223372036854775808 to 9223372036854775807).
Obviously. As documented in the manual that command can set minvalue or restart with a new value and manipulate many other properties that affect the number generation.
You should use identity columns instead
Not possible - that's not what sequences are intended for. See e.g. here for a possible implementation of a gapless number generator.
I have a BLOB field in a table that I am selecting. This field data consists only of JSON data.
If I do the following:
Select CAST(JSONBLOB as VARCHAR(2000)) from MyTable
--> this returns the value in VARCHAR FOR BIT DATA format.
I just want it as a standard string or varcher - not in bit format.
That is because I need to use JSON2BSON function to convert the JSON to BSON. JSON2BSON accepts a string but it will not accept a VarChar for BIT DATA type...
This conversation should be easy.
I am able to do the select as a VARCHAR FOR BIT DATA.. Manually COPY it using the UI. Paste it into a select literal and convert that to BSON. I need to migrate a bunch of data in this BLOB from JSON to BSON, and doing it manually won't be fast. I just want to explain how simple of a use case this should be.
What is the select command to essentially get this to work:
Select JSON2BSON(CAST(JSONBLOB as VARCHAR(2000))) from MyTable
--> Currently this fails because the CAST converts this (even though its only text characters) to VARCHAR for BIT DATA type and not standard VARCHAR.
What is the suggestion to fix this?
DB2 11 on Windows.
If the data is JSON, then the table column should be CLOB in the first place...
Having the table column a BLOB might make sense if the data is actually already BSON.
You could change the blob into a clob using the converttoclob procedure then you should be ok.
https://www.ibm.com/support/knowledgecenter/SSEPGG_11.5.0/com.ibm.db2.luw.apdv.sqlpl.doc/doc/r0055119.html
You can use this function to remove the "FOR BIT DATA" flag on a column
CREATE OR REPLACE FUNCTION DB_BINARY_TO_CHARACTER(A VARCHAR(32672 OCTETS) FOR BIT DATA)
RETURNS VARCHAR(32672 OCTETS)
NO EXTERNAL ACTION
DETERMINISTIC
BEGIN ATOMIC
RETURN A;
END
or if you are on Db2 11.5 the function SYSIBMADM.UTL_RAW.CAST_TO_VARCHAR2 will also work
I just would like to know if it is possible to limit character length with byte size for Postgres.
It would be very appreciated if you would tell me that.
Postgres version: 9.2.17
The length limit for a varchar column is in characters based on the encoding of the database. Unless you want to change your database to use a single-byte encoding (which I would strongly discourage), there is no direct way to do this.
What you can do is to use a check constraint that converts the character value to a byte array based on a specific encoding and then checks the length of the array:
alter table the_table
add constraint check_byte_length
check ( length(convert_to(the_column, 'UTF-8')) <= 42 )
Can I use nvarchar data type in plpgsql?
If so, do I have to follow the same syntax?
If not, then what is the alternative?
Just use the text or varchar types.
There's no need for, or support for, nvarchar. All PostgreSQL text-like types are always in the database's text encoding, you can't choose a 1-byte or 2-byte type like in MS SQL Server. Generally you just use a UTF-8 encoded DB, and everything works with no hassle.