The usage of defined() in the documentation:
does hstore contain non-NULL value for key?
In addition to a NULL value for an existing key, it returns FALSE also when the key does not exist.
To keep it clean, you might want to use the exist() function instead:
SELECT exist('"bla" => 1234', 'bloo');
So your query would look like
The name of the additional module hstore is derived from "hash store", because it was inspired by perl hash.
Oleg Bartunov and Teodor Sigaev - the authors of the module - say so in their presentation here:
Hstore — key/value storage (inspired by perl hash)
You can simple use hstore_to_json function to get a json out of a hstore. To change the table you can use the ALTER TABLE command.
ALTER TABLE table_name
ALTER your_column_name TYPE json USING hstore_to_json(your_column_name);
There is hstore_to_jsonb too if you want jsonb instead of json.
For anyone that runs into this question. I ran into this problem today and found a solution.
Depending on where you have the extension installed, it may not be in your search_path.
In my case, i had it installed into the schema 'shared_extensions' on the same db.
using SHOW search_path displayed $user, public, which means that it was never looking in ...
You are looking for the skeys function:
If you also need the values for each key:
select (a).key, (a).value
select each(hstore_column) as a
More details in the manual: http://www.postgresql.org/docs/current/static/hstore.html
In SQL, NULL (operator) (value) is generally NULL.
This is not unique to hstore, and is the norm for everything.
The empty string '' is different to NULL. '' || 'somestring' is 'somestring', wheras NULL || 'somestring' is NULL.
The same is true for hstore. Just like NULL + 1 is NULL.
If this is a problem for you, you should probably store empty hstore ...
This can be done, very efficiently, too. Not in a single statement, though, since SQL demands to know the return type at call time. So you need two steps. The solution involves a number of advanced techniques ...
Assuming the same table as @Denver in his answer:
CREATE TABLE hstore_test (
id serial PRIMARY KEY
, hstore_col hstore
Solution 1: Simple ...
I realize I'm a bit late—and by now you sure have it figured out—but, seeing the comment you left on Denver Timothy's answer, I thought I would leave an answer for everybody else:
select (each(hstore_col)).key from hstore_test;
This will create a row for each key contained in hstore_col, so you won't need to know what the keys are beforehand.
You're trying to use the expression item.details::hstore - 'vin'::TEXT as a PL/PgSQL statement.
Where's the result supposed to go?
At a guess, I think what you intended to write is:
item.details := item.details - 'vin'::TEXT;
i.e. "set item.details to the old value of item.details with the key vin removed".
It's kind of hard to be sure without more ...
@Craig provides a detailed explanation and the best advice to avoid the problem: define the column NOT NULL DEFAULT '' - which adds 1 byte per row to storage (typically) where the columns could be NULL instead.
The simple, standard solution for the problem at hand is COALESCE() - like with any other data type that can be NULL. It's a completely reasonable ...
you can concatenate them:
set hstore_col = hstore('new_key_1',foo.new_value_1)||hstore('new_key_2',foo.new_value_2)
Alternatively use the constructor function that accepts two arrays:
set hstore_col = hstore(array['new_key_1', 'new_key_2'],array[foo.new_value_1, foo.new_value_2])
The second solution will be easier to extend when you have more keys then ...
Sure you can.
CREATE VIEW v_ebooks AS
SELECT products_id, attributes->'device' AS device
WHERE attributes->'edition'= 'ebook';
SQL Fiddle demo.
But only for a static set of columns. Dynamic output of all possible attributes in an hstore column conflicts with the requirement that the return type has to be declared at creation time.
There are functions for doing this, supported by the hstore extension. Depending on your exact needs, you may use akeys() or skeys(). For extracting into a file which contains the ID from the table and a comma separated list of the keys:
SELECT your_id, array_to_string(akeys(hstore_column))
Again, depending on your needs, you may wrap this ...
With lots of UPDATEs, each one, no matter how small, will cause the entire row to be rewritten into a new version, as a consequence of the MVCC mechanism.
Then the old version of the row will be picked up at some point by autovacuum when it's certain that no transaction may need it, and its space will be flagged as reusable .
The constant turnover of disk ...
Original question (dupes within hstore value)
I think the root cause of your problems is explained in this quote from the manual:
Each key in an hstore is unique. If you declare an hstore with
duplicate keys, only one will be stored in the hstore and there is no
guarantee as to which will be kept.
Bold emphasis mine.
You are mistaken in assuming ...
You'll want to use the -> operator on the column (see here).
Records without the same key in other records will show as NULL.
create table hstore_test (id serial, hstore_col hstore);
insert into hstore_test (hstore_col) values ('key1=>val11, key2=>val12, key3=>val13'), ('key1=>val21, key2=>val22');
select hstore_col->'key1' as key1, ...
Usually in SQL double quotes used to specify the identifiers like tables, columns, functions and other DB objects which name contains "non-conventional" characters or have to be case-sensitive. For example it is correct PostgreSQL statement:
create table "This is#my...%TABLE" ("And&Field" int);
(It is not recommended to use such names however because ...
You need to create a set of the keys in order to be able to compare them using like.
from the_table t
where exists (select *
from skeys(t.tags) as x(tagname)
where x.tagname like '%building%');
But this is not going to be fast.
Just use the function hstore().
There are several overlaoded versions of that functions. One takes a single text array with keys and values. Another one takes two text arrays, one with keys, the other one with values. Either works for you. Demo:
SELECT hstore(array_agg(ARRAY[key, value::text])) AS option1
, hstore(array_agg(key), array_agg(value::...
With only 10-20 distinct keys, I would urgently consider one separate column per key in the same row. Unused keys stay NULL. Related case:
JSONB vs BRIN Index
That said, there is a way to get the list of distinct key names from a document type column like jsonb or hstore comparatively quickly:
Create a btree expression index on the sorted array of key ...
So I am having the same problem now that 9.6.1 is out. Here is the only thing I have found so far on-line but haven't tried it out for myself yet. I'll update this answer once I've been able to successful solve the problem.
EDIT: I followed these steps and everything works great. Hopefully when I upgrade to 9.7 it won't be so hard.
Currently on 9.5.4_1
To do it with built-in tools of Postgres and the hstore module exclusively, without involving jsonb, as requested, replace:
audit_row.row_data = hstore(NEW.*) - excluded_cols;
audit_row.row_data = hstore(
SELECT ARRAY[key, value]
FROM each(hstore(NEW.*) - excluded_cols)
WHERE value IS NOT NULL
There is no performant way to get all distinct names of keys used in an entire hstore (or jsonb) column for a table with many rows. You could used a materialized view if the list of distinct keys does not have to be perfectly up to date. But more likely, you should store your key-value pairs in a real relational table rather than in denormalized form.
CentOS 7 was released on 2014-07-07.
PostgreSQL 9.3 was released on 2013-09-09. You would think it would have 9.3, but nope. CentOS 7 uses PostgreSQL 9.2 which was released on 2012-09-10 and hits End-Of-Life in September 2017.
Find the official instructions for using the non-CentOS repos here. PostgreSQL maintains it's own packages too. The official ...
createIndex := 'CREATE INDEX idx_'
|| '_properties_crosspr_gist ON public.'
USING gist (properties)
WHERE properties @> $$"block_level_0"=>"cerber-head"$$::hstore
AND properties @> $$"block_level_1"=>"head"$$::hstore
AND properties @> $$"block_level_2"=>"cross-...
At the scope at which you're working. I think JSONB is ideal. It handles deeply nested structures and structures with array-keys. It's also standardized and in the spec for sql2016.
In addition, as I answered here, there is an extension that should help you with space consumption called ZSON,
ZSON is a PostgreSQL extension for transparent JSONB ...
You could create a table to hold the key/value pairs like such:
CREATE TABLE KEY_VALUE (
ID BIGINT, -- THIS COULD BE A FKEY TO YOUR '300K' RECORD TABLE
As long as this table is indexed properly (an index on id/key, I imagine), getting any key/value pairs you are interested in should still be very quick, even if it's ...