First alpha release of PsqlForks - Menon

Primer: PsqlForks aims to support all DB Engines that (even partially) speak Postgres (psqlforks = psql for Postgres forks).

Given that PsqlForks has been in development for a few weeks, it's time to stabilize a bit and towards that, we finally have Menon, PsqlForks first Alpha Release. Being an alpha, by definition it isn't ready for production, but it feels stable enough ... feel free to test it out!

Importantly, this fork is synced with postgres/master regularly, and should ideally sport all recent psql developments. Further, I am not a C expert and am just barely comprehending Postgres, so let me know of any 18-wheelers that I didn't see.

The release title - 'Menon', is a common sub-Caste in South-Indian state of Kerala. Selecting this nomenclature emanates from the idea of popularizing (heh!) common names and places from Kerala... and that it doesn't hurt to have an identifiable name (and while at it, add character) to a Release :) 

This release includes: 

• Decent support for Redshift:
• SQL tab completion for Redshift related variations
• \d etc. now support Redshift specifics - ENCODINGs / SORTKEYs / DISTKEY / COMPRESSION etc.
• Support Temporary Credentials using IAM Authentication (via AWS CLI)
• View detailed progress here.
• Basic support / Recognition semantics for:
• CockroachDB - view progress here
• PipelineDB
• PgBouncer
• RDS PostgreSQL

You could read more here:

• Readme: https://github.com/robins/postgres/blob/forks/src/bin/psql/README.md
• This blog: http://www.thatguyfromdelhi.com/search/label/psqlforks

For the interested:

• Upcoming Milestones: https://github.com/robins/postgres/milestones
• Existing open issues: https://github.com/robins/postgres/issues
• Feedback / Bugs? Post them here

PsqlForks supports AWS IAM authentication for Redshift

With this commit, PsqlForks ( http://psqlforks.com ) can now fetch credentials from AWS IAM. Read more about Redshift's support for generating database credentials using IAM authentication feature, here.

Since the entire AWS CLI isn't baked into PsqlForks (yet!), you'd need a working copy of AWS CLI installed / working on the host (from where psql is called).

This took a while, since I missed the basic assumption that Redshift enforces SSL and psql doesn't attempt SSLMODE by default in the first try. The fact that CYGWIN wasn't super-smooth with AWS CLI in my test installation, didn't help either.

But as they say, all's well that ends well. There are few obvious additions that are possible (such as expiration validation / re-use unexpired credentials on re-connect etc.) but this should get merged in the forks mainline soon.

I guess it's time to begin thinking of releases, instead of making the mainline jittery with feature additions such as this one.

Yenjoy!


$ psql "sslmode=require host=redshift_cluster port=5439 dbname=redshift2" -U testing1
Password for user testing1:
psql: fe_sendauth: no password supplied

$ psql -I "sslmode=require host=redshift_cluster port=5439 dbname=redshift2" -U testing1

CLI: aws redshift get-cluster-credentials --auto-create --db-user testing1 --cluster-identifier redshift2 # Informational / testing output

psql (client-version:11devel, server-version:8.0.2, engine:redshift)
SSL connection (protocol: TLSv1.2, cipher: ECDHE-RSA-AES256-GCM-SHA384, bits: 256, compression: on)
Type "help" for help.

redshift2=> select current_user;
 current_user
--------------
 testing1
(1 row)

redshift2=> \du
                     List of roles
 Role name |          Attributes           | Member of
-----------+-------------------------------+-----------
 redshift2 | Superuser, Create DB         +|
           | Password valid until infinity |
 testing1  |                               |

redshift2=> \q

$ ./psql --help | grep -i iam
  -I, --aws-iam-redshift   use temporary database credentials from AWS IAM Service

psql \d now supports Interleaved / Compound SORTKEYs (in Redshift)

In continuation of support for Redshift series, now Describe Table (for e.g. \d tbl) shows SORTKEY details. This resolves Issue #6 and shows both COMPOUND / INTERLEAVED variations along with all the column names.

This change was complicated because Redshift doesn't natively support LISTAGG() function on System / Catalog tables, which meant that I had to resort to a pretty verbose workaround. This in-turn meant that this patch shows only the first ten COMPOUND SORTKEYs of a table. Seriously speaking, it would really take an extreme corner-case, for someone to genuinely require a SORTKEY with 10+ columns.

This is not a limitation for INTERLEAVED SORTKEY since it only supports a maximum of 8 Columns.


db=# CREATE TABLE tbl_pk(custkey SMALLINT PRIMARY KEY);
CREATE TABLE
db=# \d tbl_pk
                                           Table "public.tbl_pk"
 Column  |   Type   | Encoding | DistKey | SortKey | Preload | Encryption | Collation | Nullable | Default
---------+----------+----------+---------+---------+---------+------------+-----------+----------+---------
 custkey | smallint | lzo      | f       | 0       | f       | none       |           | not null |
Indexes:
 PRIMARY KEY, btree (custkey)

db=# CREATE TABLE tbl_compound(
db(#   custkey   SMALLINT                ENCODE delta NOT NULL,
db(#   custname  INTEGER DEFAULT 10      ENCODE raw NULL,
db(#   gender    BOOLEAN                 ENCODE RAW,
db(#   address   CHAR(5)                 ENCODE LZO,
db(#   city      BIGINT identity(0, 1)   ENCODE DELTA,
db(#   state     DOUBLE PRECISION        ENCODE Runlength,
db(#   zipcode   REAL,
db(#   tempdel1  DECIMAL                 ENCODE Mostly16,
db(#   tempdel2  BIGINT                  ENCODE Mostly32,
db(#   tempdel3  DATE                    ENCODE DELTA32k,
db(#   tempdel4  TIMESTAMP               ENCODE Runlength,
db(#   tempdel5  TIMESTAMPTZ             ENCODE DELTA,
db(#   tempdel6  VARCHAR(MAX)            ENCODE text32k,
db(#   start_date VARCHAR(10)            ENCODE TEXT255
db(# )
db-# DISTSTYLE KEY
db-# DISTKEY (custname)
db-# COMPOUND SORTKEY (custkey, custname, gender, address, city, state, zipcode, tempdel1, tempdel2, tempdel3, tempdel4, tempdel5, start_date);
CREATE TABLE
db=#
db=# \d tbl_compound
                                                                 Table "public.tbl_compound"
   Column   |            Type             | Encoding  | DistKey | SortKey | Preload | Encryption | Collation | Nullable |              Default
------------+-----------------------------+-----------+---------+---------+---------+------------+-----------+----------+------------------------------------
 custkey    | smallint                    | delta     | f       | 1       | f       | none       |           | not null |
 custname   | integer                     | none      | t       | 2       | f       | none       |           |          | 10
 gender     | boolean                     | none      | f       | 3       | f       | none       |           |          |
 address    | character(5)                | lzo       | f       | 4       | f       | none       |           |          |
 city       | bigint                      | delta     | f       | 5       | f       | none       |           |          | "identity"(494055, 4, '0,1'::text)
 state      | double precision            | runlength | f       | 6       | f       | none       |           |          |
 zipcode    | real                        | none      | f       | 7       | f       | none       |           |          |
 tempdel1   | numeric(18,0)               | mostly16  | f       | 8       | f       | none       |           |          |
 tempdel2   | bigint                      | mostly32  | f       | 9       | f       | none       |           |          |
 tempdel3   | date                        | delta32k  | f       | 10      | f       | none       |           |          |
 tempdel4   | timestamp without time zone | runlength | f       | 11      | f       | none       |           |          |
 tempdel5   | timestamp with time zone    | delta     | f       | 12      | f       | none       |           |          |
 tempdel6   | character varying(65535)    | text32k   | f       | 0       | f       | none       |           |          |
 start_date | character varying(10)       | text255   | f       | 13      | f       | none       |           |          |
Indexes:
 COMPOUND SORTKEY (address,tempdel2,start_date,custkey,zipcode,tempdel4,city,state,tempdel3,custname)

db=# CREATE TABLE tbl_interleaved(custkey SMALLINT) INTERLEAVED SORTKEY (custkey);
CREATE TABLE
db=# \d tbl_interleaved
                                      Table "public.tbl_interleaved"
 Column  |   Type   | Encoding | DistKey | SortKey | Preload | Encryption | Collation | Nullable | Default
---------+----------+----------+---------+---------+---------+------------+-----------+----------+---------
 custkey | smallint | none     | f       | 1       | f       | none       |           |          |
Indexes:
 INTERLEAVED SORTKEY (custkey)

As a side-note, there is a consideration as to whether this should be on a separate section of its own (and not under Indexes, which it clearly isn't). May be another day. Happy Redshifting :) !

Update (15th Sep 2017):
This project has now been named PsqlForks!

psql \d now supports DISTKEY / SORTKEY / ENCODING (in Redshift)

This is in continuation of my work for (my forked version of) psql to better support Redshift (read more here).

Now \d table provides some additional Redshift specific table properties such as:

• DISTKEY
• SORTKEY
• COMPRESSION (ENCODING)
• ENCRYPTION

Sample:

t3=# CREATE TABLE customer(

  custkey   SMALLINT                ENCODE delta NOT NULL,

  custname  INTEGER DEFAULT 10      ENCODE raw NULL,

  gender    BOOLEAN                 ENCODE RAW,

  address   CHAR(5)                 ENCODE LZO,

  city      BIGINT identity(0, 1)   ENCODE DELTA,

  state     DOUBLE PRECISION        ENCODE Runlength,

  zipcode   REAL,

  tempdel1  DECIMAL                 ENCODE Mostly16,

  tempdel2  BIGINT                  ENCODE Mostly32,

  tempdel3  DATE                    ENCODE DELTA32k,

  tempdel4  TIMESTAMP               ENCODE Runlength,

  tempdel5  TIMESTAMPTZ             ENCODE DELTA,

  tempdel6  VARCHAR(MAX)            ENCODE text32k,

  start_date VARCHAR(10)            ENCODE TEXT255

)

DISTSTYLE KEY

DISTKEY (custname)

INTERLEAVED SORTKEY (custkey, custname);

CREATE TABLE

t3=# \d customer

                                                                   TABLE "public.customer"

   Column   |            Type             | Encoding  | DistKey | SortKey | Preload | Encryption | Collation | Nullable |              Default

------------+-----------------------------+-----------+---------+---------+---------+------------+-----------+----------+------------------------------------

 custkey    | smallint                    | delta     | f       | 1       | f       | none       |           | not null |

 custname   | integer                     | none      | t       | 2       | f       | none       |           |          | 10

 gender     | boolean                     | none      | f       | 0       | f       | none       |           |          |

 address    | character(5)                | lzo       | f       | 0       | f       | none       |           |          |

 city       | bigint                      | delta     | f       | 0       | f       | none       |           |          | "identity"(493983, 4, '0,1'::text)

 state      | double precision            | runlength | f       | 0       | f       | none       |           |          |

 zipcode    | real                        | none      | f       | 0       | f       | none       |           |          |

 tempdel1   | numeric(18,0)               | mostly16  | f       | 0       | f       | none       |           |          |

 tempdel2   | bigint                      | mostly32  | f       | 0       | f       | none       |           |          |

 tempdel3   | date                        | delta32k  | f       | 0       | f       | none       |           |          |

 tempdel4   | timestamp without time zone | runlength | f       | 0       | f       | none       |           |          |

 tempdel5   | timestamp with time zone    | delta     | f       | 0       | f       | none       |           |          |

 tempdel6   | character varying(65535)    | text32k   | f       | 0       | f       | none       |           |          |

 start_date | character varying(10)       | text255   | f       | 0       | f       | none       |           |          |

Now that a few 'ToDos' are listed on Github Issues, next would probably involve working on this ticket, which aims at elaborate SORTKEY details (such as INTERLEAVED / COMPOUND) etc. when using Describe Table.

Update (15th Sep 2017):
This project has now been named PsqlForks!

Redshift support for psql

Am sure you know that psql doesn't go out of it's way to support Postgres' forks natively. I obviously understand the reasoning, which allowed me to find a gap that I could fill here.

The existing features (in psql) that work with any Postgres fork (like Redshift) are entirely because it is a fork of Postgres. Since I use psql heavily at work, last week I decided to begin maintaining a Postgres fork that better supports (Postgres forks, but initially) Redshift. As always, unless explicitly mentioned, this is entirely an unofficial effort.

The 'redshift' branch of this Postgres code-base, is aimed at supporting Redshift in many ways:

• Support Redshift related artifacts
• Redshift specific SQL Commands / variations
• Redshift Libraries
• Support AWS specific artifacts
• For e.g. AWS Regions
• Support Redshift specific changes
• For e.g. "/d table" etc.

The idea is:

• Maintain this branch for the long-term
• At least as long as I have an accessible Redshift cluster
• Down the line look at whether other Postgres forks (for e.g. RDS Postgres) need such special attention
• Although nothing much stands out yet
• Except some rare exceptions like this or this, which do need to go through an arduous long wait / process of refinement.
• Change the default port to 5439 (or whatever the flavour supports)
• ...with an evil grin ;)
• Additionally, as far as possible:
• Keep submitting Postgres related patches back to Postgres master
• Keep this branch up to date with Postgres master

Update (31st August 2017)

• Currently this branch supports most Redshift specific SQL commands such as
• CREATE LIBRARY
• CREATE TABLE (DISTKEY / DISTSTYLE / ...)
• Returns non-SQL items like
• ENCODINGs (a.k.a. Compressions like ZSTD / LZO etc )
• REGIONs (for e.g. US-EAST-1 etc.)
• Of course some complex variants (for e.g. GRANT SELECT, UPDATE ON ALL TABLES IN SCHEMA TO GROUP xxx ) don't automatically come up with tab-complete feature. This is primarily because psql's tab-complete feature isn't very powerful to cater to all such scenarios which in turn is because psql's auto-complete isn't a full-fledged parser to begin with.
• In a nutshell, this branch is now in a pretty good shape to auto-complete the most common Redshift specific SQL Syntax.
• The best part is that this still merges perfectly with Postgres mainline!

Let me know if you find anything that needs inclusion, or if I missed something.

====================================

$  psql -U redshift_user -h localhost -E -p 5439 db
psql (client-version:11devel, server-version:8.0.2, engine:redshift)
Type "help" for help.

db=#

Symbols in Redshift User Passwords work just fine

Recently read a few posts / discussions about people doubting Redshift not accepting (working-well with) ASCII symbols in User-Passwords.

It felt like a good time to write this short post showing that Redshift (Engine) seems to work fine with (non-alphanumeric) (printable) ASCII symbols.

You can see a few things (in the sample output given below):

• All non-alphanumeric printable ASCII characters worked fine (at least all that my US-International / QWERTY keyboard could throw at it)
• For those who also need ' (single-quote) and " (double-quote) you could always use $$ as quote-delimiters
• You still need at least One of each of the following:
• Upper-Case English-Letter
• Lower-Case English-Letter
• One Digit / Numeral

------------------------------------------------------------
# psql -U adminuser -h  rs_cluster -p 5439 db

psql (9.6.3, server 8.0.2)
Type "help" for help.

rs_cluster adminuser@db-# alter user userb with password 'Aa1~!@#$%^&*()_+-`{}[]|";:,<.>/?';
ALTER USER
Time: 237.012 ms
rs_cluster adminuser@db-# \q

# psql -U userb -h  rs_cluster -p 5439 db
Password for user userb:

psql (9.6.3, server 8.0.2)
Type "help" for help.

rs_cluster userb@db-# alter user userb with password $$Aa1~!@#$%^&*()_+-`{}[]|";:,<.>/?'"$$;
ALTER USER
Time: 191.505 ms
rs_cluster adminuser@db-# \q

# psql -U userb -h  rs_cluster -p 5439 db
Password for user userb:

psql (9.6.3, server 8.0.2)
Type "help" for help.

rs_cluster userb@db-#
------------------------------------------------------------

Using generate_series() in Redshift

Considering that Redshift clearly states that it doesn't support (the commonly used postgres function) generate_series(), it gets very frustrating if you just want to fill a table with a lot of rows and can't without a valid data-source.

Solution (Generates a billion integers on my test-cluster):

--INSERT INTO tbl
WITH x AS (
  SELECT 1 
  FROM stl_connection_log a, stl_connection_log b, stl_connection_log c
  -- LIMIT 100
)
  SELECT row_number() over (order by 1) FROM x;

For a Redshift server with even a basic level of login activity, this should generate enough rows. For e.g. On my test cluster, where I am the only user, this currently generates 4034866688 (4 billion) rows :) !

Interestingly, irrespective of the document, generate_series() actually does work on Redshift:

# select b from generate_series(1,3) as a(b);
┌───┐
│ b │
├───┤
│ 1 │
│ 2 │
│ 3 │
└───┘
(3 rows)

The reason why this wouldn't let you insert any rows to your table though, is that this is a Leader-Node-Only function, whereas INSERTs (on any non-single Redshift Cluster) are run on the Compute Nodes (which don't know about this function).

The reason why the above works, is ROW_NUMBER() and CROSS JOIN allow us to generate a large number of rows, but for that, the initial data-set (here the STL_CONNECTION_LOG System Table) should have at least some rows to multiply on! You could use any other system table (that is available on Compute Nodes) if required, for some other purpose.

Play On!

Redshift Limitations

Recently have been toying around with Redshift (a popular Data-Warehouse tool by AWS) a little bit and see some minor but obvious limitations in SQL limitations:

FULL OUTER JOIN + ON Func(x) = Func(y) : Not Supported

Although Redshift supports most variants of FULL OUTER JOIN, however, when the JOIN condition contains a function on both sides, it gives up complaining "ERROR:  XX000: could not devise a query plan for the given query".

CREATE TABLE x (a integer);
INSERT INTO x VALUES (1);  

SELECT x1.a, x2.a
FROM x x1
FULL OUTER JOIN x x2
     ON LOWER(x1.a) = LOWER(x2.a); -- Fails
  -- ON LOWER(x1.a) = x2.a; -- Works

  -- ON x1.a = LOWER(x2.a); -- Works

  -- ON x1.a = x2.a; -- Obviously Works

Workaround: The obvious way around it is to move one of the functions to a separate SQL (for e.g create a Temp Table and use that in the final computation), something like this:

CREATE TEMP TABLE x1(a) AS SELECT LOWER(a) FROM x;

SELECT x1.a, x2.a

FROM x1

FULL OUTER JOIN x x2

ON x1.a = LOWER(x2.a); -- Works