yangyang

9 ms·

61.
by yangyang 12y ago
Indeed - quite a lot of stations already have platform staff for checking doors and notifying the driver that it's OK to close. I suppose it would depend on the ratio of active trains to stations as it which is most efficient. I believ
62.
by yangyang 12y ago
To a point. They walk up and down the train, do the door opening / closing, check tickets here and there, and occasionally drive the train (though it always seems painfully slow when under manual control). I don't know how they&#x
63.
by yangyang 12y ago
He / she edited after I replied.
64.
by yangyang 12y ago
They definitely had them before that incident (which was at Shadwell IIRC).
65.
by yangyang 12y ago
And yet the Docklands Light Railway, also in London, and also under TfL control (though operation is outsourced to Serco, soon to be Keolis/Amey) has run without drivers (but with "train captains") for its entire history, ove
66.
by yangyang 12y ago
IMCS [1] already uses SIMD vector instructions. [1] http://www.pgcon.org/2014/schedule/attachments/322_IMCS.pdf
67.
by yangyang 12y ago
It sounds like it was precisely because there was more low-hanging fruit. I think column-store databases are far more amenable to vectorised processing. I'm not aware of any row-store databases which do it, and most research into it ha
68.
by yangyang 12y ago
Take a look at MonetDB, an open source column store database [1]. There was a commercialised extension to that called X100 targeting cache efficiency [2]. That became VectorWise [3]. [1] http://www.monetdb.org [2] http:/&#
69.
by yangyang 12y ago
I can't imagine this would ever get into core Postgres. It's a very specific extension.
70.
by yangyang 12y ago
There are some other interesting PostgreSQL FDW extensions targeting speed. PGStrom uses the GPU: https://wiki.postgresql.org/wiki/PGStrom PGOpenCL: http://wiki.postgresql.org/images/6/65&#x2F
71.
by yangyang 12y ago
If you read through it, this is a change to the Citus cstore_fdw extension, which stores data outside PostgreSQL and queries it using the PostgreSQL Foreign Data Wrapper API (see https://wiki.postgresql.org/wiki/Foreign
72.
by yangyang 12y ago
I meant as a self-contained type. PostgreSQL doesn't support nested tables. The "associative" in associative array implies association is a property of the data structure, not the way you happen to be using it.
73.
by yangyang 12y ago
CREATE OR REPLACE FUNCTION get_people() RETURNS person[] LANGUAGE sql AS person is a composite type, defined further up. The square brackets indicate an array of that type.
74.
by yangyang 12y ago
A text column with a list of {comma, space, ...}-delimited values representing a set, e.g. of tags, is something you occasionally see.
75.
by yangyang 12y ago
> Or if you're using Postgres, you can return the metadata as an associative array. E.G. http://stackoverflow.com/a/11942726 That's not an associative array, it's just an array of a composite type. Th
76.
by yangyang 12y ago
This is the thing I was actually thinking of when I posted the above. This is a background worker (runs within PostgreSQL) speaking the mongo wire protocol: https://github.com/umitanuki/mongres Again, very basic PoC.
77.
by yangyang 12y ago
You're only avoiding putting the whole thing on the wire twice.
78.
by yangyang 12y ago
You can't. Others in this conversation have pointed out this is targeted for 9.5, though it may available as an extension before that.
79.
by yangyang 12y ago
Table groups look rather like hierarchical databases [1], which were the norm before relational databases came along. Do bear in mind that you'll never get MongoDB-style in-place updates in PostgreSQL, due to MVCC. You may save a round
80.
by yangyang 12y ago
There is an interesting post about locking and performance when implementing queues in PostgreSQL by one of the PostgreSQL contributors here: http://johtopg.blogspot.se/2010/12/queues-in-sql.html
81.
by yangyang 12y ago
The improvements to hstore (primarily to make it hierarchical and add array support) ended up becoming jsonb.
82.
by yangyang 12y ago
I get the feeling that a sizeable proportion of NoSQL users don't have much knowledge of relational databases at all, never mind replication. If you just want to persist some JSON data you already have, I suppose it is quite a large le
83.
by yangyang 12y ago
These are the slides from an interesting presentation by one of the people that did a lot of the work for the new jsonb type in 9.4, and associated index improvements: http://www.sraoss.co.jp/event_seminar/2014/201
84.
by yangyang 12y ago
Note that on the Github repo for this benchmark, the README mentions that: "... later versions will include a complete range of workloads (including deleting, updating, appending, and complex select operations) and they will also evalu
85.
by yangyang 12y ago
You do have a point. PostgreSQL undoubtedly has many more knobs and do you do end up having to learn a fair bit to do stuff like replication. I'd rather spend more time understanding things up-front and have a reliable solution rather
86.
by yangyang 12y ago
Streaming replication is really not hard to set up in PostgreSQL. It is cluster-level; if you want to replicate a single database you'll need to use a 3rd party solution like Slony or Burcado (logical replication built on features in 9
87.
by yangyang 12y ago
Why does the format the data is stored in matter more than the data itself? JSON or columns in rows - it's not fundamentally different.
88.
by yangyang 12y ago
That's not strictly true; PL/Perl is (obviously) a programming language and is available in trusted (with certain operations disabled) and untrusted variants: see [1]. The issue with PL/Python is that it's nigh on imposs
89.
by yangyang 12y ago
There are plenty of database that don't fit into RAM completely and are perfectly usable. It depends on what you can fit in buffer cache / OS page cache. The whole point of btree indexes is that they're efficient to query f
90.
by yangyang 12y ago
The nice thing about using an RDBMS with JSON support, rather than a NoSQL solution, is that you can store all the fixed-schema stuff in column as usual, and benefit from the performance, consistency, ease of joins and so on with that, but

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