I tried searching for it but couldn't find out
What is the best way to copy data from Redshift to Postgresql Database ?
using Talend job/any other tool/code ,etc
anyhow i want to transfer data from Redshift to PostgreSQL database
also,you can use any third party database tool if it has similar kind of functionality.
Also,as far as I know,we can do so using AWS Data Migration Service,but not sure our source db and destination db matches that criteria or not
Can anyone please suggest something better ?
The way I do it is with a Postgres Foreign Data Wrapper and dblink,
This way, the redshift table is available directly within Postgres.
Follow the instructions here to set it up https://aws.amazon.com/blogs/big-data/join-amazon-redshift-and-amazon-rds-postgresql-with-dblink/
The important part of that link is this code:
CREATE EXTENSION postgres_fdw;
CREATE EXTENSION dblink;
CREATE SERVER foreign_server
FOREIGN DATA WRAPPER postgres_fdw
OPTIONS (host '<amazon_redshift _ip>', port '<port>', dbname '<database_name>', sslmode 'require');
CREATE USER MAPPING FOR <rds_postgresql_username>
SERVER foreign_server
OPTIONS (user '<amazon_redshift_username>', password '<password>');
For my use case I then set up a postgres materialised view with indexes based upon that.
create materialized view if not exists your_new_view as
SELECT some,
columns,
etc
FROM dblink('foreign_server'::text, '
<the redshift sql>
'::text) t1(some bigint, columns bigint, etc character varying(50));
create unique index if not exists index1
on your_new_view (some);
create index if not exists index2
on your_new_view (columns);
Then on a regular basis I run (on postgres)
REFRESH MATERIALIZED VIEW your_new_view;
or
REFRESH MATERIALIZED VIEW CONCURRENTLY your_new_view;
In the past, I managed to transfer data from one PostgreSQL database to another by doing a pg_dump and piping the output as an SQL command to the second instance.
Amazon Redshift is based on PostgreSQL, so this method should work, too.
You can control whether pg_dump should include the DDL to create tables, or whether it should just load the data (--data-only).
See: PostgreSQL: Documentation: 8.0: pg_dump
I was reading an article on secure storage of credentials with postgres which recommended randomized uuids vs an autoincrementing id.
In raw postgresql it would be something like:
id uuid NOT NULL DEFAULT gen_random_uuid() PRIMARY KEY
However, with eloquent I can't figure out how to achieve something like this. The eloquent docs for 5.4 mention ->storedAs($expression) which is unfortunately limited to MySQL. Is this simply not possible with postgres?
Try ->default(DB::raw('gen_random_uuid()'));
It is exists in query builder documentation
I would like to link a MS Access table to a table in PG admin if it is possible for use in a Postgres query. I have searched for an answer but all I can find is answers for listing postgres tables in Access which is almost the opposite of what I want to do.
I want to be able to access the data entered in an access form without having to continually import the data into a table in PG Admin.
I'm not even sure that is possible but any method that is easier than importing the table into PG Admin every day would be useful.
Thanks
Gary
Try the PostgreSQL OGR Foreign Data Wrapper. Its built for spatial data, but it works perfectly well with non-spatial tables. If you have the PostGIS extension installed you will already have it.
https://github.com/pramsey/pgsql-ogr-fdw
There are several examples on that page, but the command
ogr_fdw_info -s <pathToAccessFile> -l <tablename>
will return create server and a create foreign table statements which you can edit as required then run in pgAdmin.
I am trying to solve a problem where I need to generate a non-sequential and cryptographically random primary key as each record is inserted into a table.
The reason for this is each record is generated from an email list, but those records should not be able to be linked back to those email addresses (secret ballot situation). If someone managed to access the email list, they could derive from the insertion order who supplied the data for each record.
Is it possible to do this without generating an id of some kind in the application code, and be done purely in PostgreSQL? If not, what is the next best solution?
It seems that the best choice is to use pgcrypto and do the following:
CREATE EXTENSION pgcrypto;
CREATE TABLE whatever (
id uuid PRIMARY KEY DEFAULT gen_random_uuid()
)
The PostgreSQL 9.4 documentation on pgcrypto states that gen_random_uuid() generates a cryptographically random V4 UUID, which suits this situation perfectly.
Its good practice to Go with uuid as you can check out this link as well.
Advantages and Disadvantages of UUID and
whats-your-opinion-on-using-uuids-as-database-row-identifiers-particularly-in
Note: You need to enable the pgcrypto (only PostgreSQL >= 9.4) or uuid-ossp extension to generate random UUIDs..
pgcrypto generator function
uuid-ossp generator functions
Hope this help you !!!
Another option is to use encryption to generate the unique row keys. Simply encrypt the numbers 0, 1, 2, 3, ... in turn using a block cypher. Provided you always use the same cypher key, the outputs are guaranteed unique because the inputs are unique. For 64 bit row keys use 3DES, for 128 bit row keys use AES. For other sizes use Hasty Pudding cypher, which can work with effectively any block size you want.
Is it possible to JOIN rows from two separate postgres databases?
I am working with system with couple databases in one server and sometimes I really need such a feature.
According to http://wiki.postgresql.org/wiki/FAQ
There is no way to query a database other than the current one.
Because PostgreSQL loads database-specific system catalogs, it is
uncertain how a cross-database query should even behave.
contrib/dblink allows cross-database queries using function calls. Of
course, a client can also make simultaneous connections to different
databases and merge the results on the client side.
EDIT: 3 years later (march 2014), this FAQ entry has been revised and is more helpful:
How do I perform queries using multiple databases?
There is no way to directly query a database other than the current
one. Because PostgreSQL loads database-specific system catalogs, it is
uncertain how a cross-database query should even behave.
The SQL/MED support in PostgreSQL allows a "foreign data wrapper" to
be created, linking tables in a remote database to the local database.
The remote database might be another database on the same PostgreSQL
instance, or a database half way around the world, it doesn't matter.
postgres_fdw is built-in to PostgreSQL 9.3 and includes read/write
support; a read-only version for 9.2 can be compiled and installed as
a contrib module.
contrib/dblink allows cross-database queries using function calls and
is available for much older PostgreSQL versions. Unlike postgres_fdw
it can't "push down" conditions to the remote server, so it'll often
land up fetching a lot more data than you need.
Of course, a client can also make simultaneous connections to
different databases and merge the results on the client side.
Forget about dblink!
Say hello to Postgres_FDW:
To prepare for remote access using postgres_fdw:
Install the postgres_fdw extension using CREATE EXTENSION.
Create a foreign server object, using CREATE SERVER, to represent each remote database you want to connect to. Specify connection
information, except user, and password, as options of the server
object.
Create a user mapping, using CREATE USER MAPPING, for each database user you want to allow to access each foreign server. Specify
the remote user name and password to use as user and password options
of the user mapping.
Create a foreign table, using CREATE FOREIGN TABLE or IMPORT FOREIGN SCHEMA, for each remote table you want to access. The columns
of the foreign table must match the referenced remote table. You can,
however, use table and/or column names different from the remote
table's, if you specify the correct remote names as options of the
foreign table object.
Now you need only SELECT from a foreign table to access the data
stored in its underlying remote table.
It's really useful even on large data.
Yes, it is possible to do this using dblink albeit with significant performance considerations.
The following example will require the current SQL user to have permissions on both databases. If db2 is not located on the same cluster, then you will need to replace dbname=db2 with the full connection string defined in the dblink documentation.
SELECT *
FROM table1 tb1
LEFT JOIN (
SELECT *
FROM dblink('dbname=db2','SELECT id, code FROM table2')
AS tb2(id int, code text);
) AS tb2 ON tb2.column = tb1.column;
If table2 is very large, you could have performance issues because the sub-query loads up the entire table2 before performing the join.
No you can't. You could use dblink to connect from one database to another database, but that won't help if you're looking for JOIN's.
You can't use different SCHEMA's within a single database to store all you data?
Just a few steps and You can reach the goal:
follow this reference step by step
WE HAVE BEEN CONNECTED TO DB2 WITH TABLE TBL2 AND COLUMN COL2
ALSO THERE IS DB1 WITH TBL1 AND COLUMN COL1
*** connecting to second db ie db2
Now just **copy paste the 1-7 processes** (make sure u use correct username and password and ofcourse db name)
1.**CREATE EXTENSION dblink;**
2.**SELECT pg_namespace.nspname, pg_proc.proname
FROM pg_proc, pg_namespace
WHERE pg_proc.pronamespace=pg_namespace.oid
AND pg_proc.proname LIKE '%dblink%';**
3.**SELECT dblink_connect('host=localhost user=postgres password=postgres dbname=db1');**
4.**CREATE FOREIGN DATA WRAPPER postgres VALIDATOR postgresql_fdw_validator;**
5.**CREATE SERVER postgres2 FOREIGN DATA WRAPPER postgres OPTIONS (hostaddr '127.0.0.1', dbname 'db1');**
6.**CREATE USER MAPPING FOR postgres SERVER postgres2 OPTIONS (user 'postgres', password 'postgres');**
7.**SELECT dblink_connect('postgres2');**
---Now, you can SELECT the data of Database_One from Database_Two and even join both db results:
**SELECT * FROM public.dblink
('postgres2','SELECT col1,um_name FROM public.tbl1 ')
AS DATA(um_userid INTEGER),tbl2 where DATA.col1=tbl2.col2;**
You can also Check this :[How to join two tables of different databases together in postgresql [\[working finely in version 9.4\]][1]
You need to use dblink...as araqnid mentioned above, something like this works fine:
select ST.Table_Name, ST.Column_Name, DV.Table_Name, DV.Column_Name, *
from information_schema.Columns ST
full outer join dblink('dbname=otherdatabase','select Table_Name,
Column_Name from information_schema.Columns') DV(Table_Name text,
Column_Name text)
on ST.Table_Name = DV.Table_name
and ST.Column_Name = DV.Column_Name
where ST.Column_Name is null or DV.Column_Name is NULL
You have use dblink extension of postgresql.
Reference take from this Article:
DbLink extension of PostgreSQL which is used to connect one database to another database.
Install DbLink extension.
CREATE EXTENSION dblink;
Verify DbLink:
SELECT pg_namespace.nspname, pg_proc.proname
FROM pg_proc, pg_namespace
WHERE pg_proc.pronamespace=pg_namespace.oid
AND pg_proc.proname LIKE '%dblink%';
I have already prepared full demonstration on this. Please visit my post to learn step by step for executing cross database query in Postgresql.
Cannot be done? Of course we can, without special extensions. In our case, we had to compare two tables from different database servers, e.g. ACC and PROD, hence an even harder case than from most answers. Especially because ACC and PROD are deliberately on different servers to create a barrier, so you will not easily gain enough rights to perform a GRANT USAGE ON FOREIGN SERVER.
The obvious solution is to export both tables, and import both in the same database, e.g. DEV, or your own local db, under appropriate names, e.g. table1_acc and table1_prod, or schemas like acc and prod. Then, you may JOIN those with no special problems.