postgresql-9.4 | 易学教程

Create nested json from sql query postgres 9.4

阅读更多关于 Create nested json from sql query postgres 9.4

问题 I need to get as a result from query fully structured JSON. I can see in postgres that there are some built in functions that may be useful. As an example I created a structure as follows: -- Table: person -- DROP TABLE person; CREATE TABLE person ( id integer NOT NULL, name character varying(30), CONSTRAINT person_pk PRIMARY KEY (id) ) WITH ( OIDS=FALSE ); ALTER TABLE person OWNER TO postgres; -- Table: car -- DROP TABLE car; CREATE TABLE car ( id integer NOT NULL, type character varying(30)

Indexing jsonb for numeric comparison of fields

阅读更多关于 Indexing jsonb for numeric comparison of fields

I've defined a simple table with create table resources (id serial primary key, fields jsonb); And it contains data with keys (drawn from a large set) and values between 1 and 100, like: id | fields --------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1 | {"tex": 23, "blair": 46, "cubic": 50, "raider": 57, "retard": 53, "hoariest": 78, "suturing": 25, "apostolic": 22, "unloosing": 37, "flagellated": 85} 2 | {"egoist": 75, "poshest": 0,

Roughly how fast is JSON -> JSONB column conversion in Postgres 9.4

阅读更多关于 Roughly how fast is JSON -> JSONB column conversion in Postgres 9.4

问题 I'm looking to migrate from Postgres 9.3 to 9.4, and have a lot of data in JSON columns. While it's fine, I wanted to have a look at migrating to the more efficient column storage (which JSONB seems to be — a really exciting piece of tech!). To actually migrate, I want to know migration characteristics for something like ALTER TABLE table_with_json ALTER COLUMN my_json SET DATA TYPE jsonb USING my_json::jsonb; (from this helpful question). Ideally, it would be good to know how long it takes

Difference between set, \set and \pset in psql

阅读更多关于 Difference between set, \set and \pset in psql

问题 I get a little confused some times when working with psql between when to use a set vs. \set vs. \pset . I think that: set is for session variables on my connection to the db. For example SET ROLE dba ; \set is for local variables for this psql session. For example \set time 'select current_timestamp' \pset is for psql settings for this psql session. For example '\pset border 2' But, I've never found what I thought was a good explanation of each. Are my assumptions above correct? I'm using

Join tables using a value inside a JSONB column

阅读更多关于 Join tables using a value inside a JSONB column

问题 There are two tables: Authorized Contacts ( auth_contacts ): ( userid varchar contacts jsonb ) contacts contains an array of contacts with attributes {contact_id, type} discussion : ( contact_id varchar discussion_id varchar discussion_details jsonb ) The table auth_contacts has at least 100k records making it non JSONB type is not appropriate according as it would double or triple the amount of records. Sample data for auth_contacts : userid | contacts '11111' | '{"contact": [{"type": "type

How do you create a Postgresql JSONB array in array index?

阅读更多关于 How do you create a Postgresql JSONB array in array index?

I have structure like this: user_id, a. a is of type jsonb and has the following structure: { b: [ {ids: [1,2,3,4]}, {ids: [2,3,4]}, {ids: [1,2,4]}, ... ] } How would I make an index that enabled me to find all users (user_id) that has a certain id in the ids list? Is a GIN index what you want? It seems that you first need to organized the IDs into a form that is more tractable. I'm more familiar with Python than I am with the PostgreSQL ways of manipulating JSON, so I used PL/Python for this purpose. DROP TABLE IF EXISTS ids; CREATE TABLE ids (user_id integer, a jsonb); INSERT INTO ids VALUES

What lock, if any, does 'CREATE TRIGGER' use in PostgreSQL 9.4.2

阅读更多关于 What lock, if any, does 'CREATE TRIGGER' use in PostgreSQL 9.4.2

according to postgres-xl , CREATE TRIGGER uses the SHARE ROW EXCLUSIVE lock, but according to the official Postgres docs for SHARE ROW EXCLUSIVE : This lock mode is not automatically acquired by any PostgreSQL command. You're comparing Postgres-XL with the main PostgreSQL documentation. Two different products, albeit with a shared history. Postgres-XL has lots of changes from stock PostgreSQL. CREATE TRIGGER should be listed in the Pg docs and isn't, though, and that's an oversight. A quick look at the source code shows that CREATE TRIGGER takes a ShareRowExclusiveLock , so in this case XL's

Duplicate (repeat) rows in sql query result

阅读更多关于 Duplicate (repeat) rows in sql query result

Let's say I have a table with two rows id | value | ----+-------+ 1 | 2 | 2 | 3 | I want to write a query that will duplicate (repeat) each row based on the value. I want this result (5 rows total): id | value | ----+-------+ 1 | 2 | 1 | 2 | 2 | 3 | 2 | 3 | 2 | 3 | I'm using PostgreSQL 9.4. You can use generate_series() : select t.id, t.value from (select t.id, t.value, generate_series(1, t.value) from t ) t; You can do the same thing with a lateral join: select t.id, t.value from t, lateral generate_series(1, t.value); 来源： https://stackoverflow.com/questions/35293084/duplicate-repeat-rows-in

Why can't I query directly on jsonb_array_elements?

阅读更多关于 Why can't I query directly on jsonb_array_elements?

问题 I have data stored as jsonb in a column called "data": {'people': [{"name": "Bob", "Occupation": "janitor"}, {"name": "Susan", "Occupation", "CEO"}]} I can query this via: SELECT mydata.pk FROM mydata, jsonb_array_elements(mydata.data->'people') AS a WHERE (a->>'name') = 'bob' Why can't I substitute "a" for the jsonb_array_elements(...)?: SELECT mydata.pk FROM mydata WHERE (jsonb_array_elements(mydata.data->'people')->>'name') = 'bob' Instead, I get the following: ERROR: argument of WHERE

How do I get the type of an array's elements?

阅读更多关于 How do I get the type of an array's elements?

I'm writing a polymorphic PL/pgSQL function that iterates over an array. I am interested in using FOREACH , however I cannot figure out how to declare a temporary variable with the right type. My function is below, for more information see the comment on line 4. CREATE OR REPLACE FUNCTION uniq(ary anyarray) RETURNS anyarray AS $$ DECLARE ret ary%TYPE := '{}'; v ???; -- how do I get the element type of @ary@? BEGIN IF ary IS NULL THEN return NULL; END IF; FOREACH v IN ARRAY ary LOOP IF NOT v = any(ret) THEN ret = array_append(ret, v); END IF; END LOOP; RETURN ret; END; $$ LANGUAGE plpgsql;