I'm working in Postgres 9.6.5. I have the following table:
id | integer
data | jsonb
The data in the data column is nested, in the form:
{ 'identification': { 'registration_number': 'foo' }}
I'd like to index registration_number, so I can query on it. I've tried this (based on this answer):
CREATE INDEX ON mytable((data->>'identification'->>'registration_number'));
But got this:
ERROR: operator does not exist: text ->> unknown
LINE 1: CREATE INDEX ON psc((data->>'identification'->>'registration... ^
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
What am I doing wrong?
You want:
CREATE INDEX ON mytable((data -> 'identification' ->> 'registration_number'));
The -> operator returns the jsonb object under the key, and the ->> operator returns the jsonb object under the key as text. The most notable difference between the two operators is that ->> will "unwrap" string values (i.e. remove double quotes from the TEXT representation).
The error you're seeing is reported because data ->> 'identification' returns text, and the subsequent ->> is not defined for the text type.
Since version 9.3 Postgres has the #> and #>> operators. This operators allow the user to specify a path (using an array of text) inside jsonb column to get the value.
You could use this operator to achieve your goal in a simpler way.
CREATE INDEX ON mytable((data #>> '{identification, registration_number}'));
Related
I am using postgresql 11 and I have a jsonb field.
amount
----------------------------------------
{"value": "3590", "currency": "AUD"}
I can use this syntax to select the nested field value: select amount->'value'.
but I don't know how I can convert it to integer and sum it, like select sum(amount->'value') from
I got this error: HINT: No function matches the given name and argument types. You might need to add explicit type casts.
I tried to convert it by
select sum(amount->'value')::DECIMAL
select sum(TO_NUMBER(amount->'value'))
but none of them working. What is the correct way to do that?
Use the ->> operator to get the value as text:
https://www.postgresql.org/docs/11/functions-json.html
SELECT SUM((amount->>'value')::INT)
I get this error when querying with a json column:
(psycopg2.ProgrammingError) operator does not exist: json = text
The column is defined as JSON with SQLAlchemy:
json_data = db.Column(db.JSON, nullable=False)
How do you compare with Postgres?
There is no equality (or inequality) operator for the data type json. If you need to test the value as a whole, you might cast to jsonb:
... WHERE json_data::jsonb = jsonb '{}';
Or cast to text for simple cases:
... WHERE json_data::text = '{}';
But there are many valid text representations for the same json value - which is the reason why Postgres does not implement equality / inequality operators for the type.
See:
How to query a json column for empty objects?
I have a field that is of type jsonb in a PostgreSQL database.
Example:
{"timestamp":"2016-12-14T04:15:04.836Z","receiptResult":{"status":"successful","timestamp":"2016-12-14T04:15:04.739Z","notes":"Customer Accepted"}}
How can I only return the "notes" in a select statement, I've tried:
SELECT data::json->>'notes' as notes
But nothing is returned, if I use:
SELECT data::json->'receiptResult' as notes;
It returns:
{"status":"successful","timestamp":"2016-114T04:15:04.739Z","notes":"Customer Accepted"}
But I only need the text after "notes".
Inside key receiptResult has another JSON object, you cannot access it in top-level. Try this:
WITH sample AS (
SELECT '{"timestamp":"2016-12-14T04:15:04.836Z","receiptResult":{"status":"successful","timestamp":"2016-12-14T04:15:04.739Z","notes":"Customer Accepted"}}'::jsonb AS my_column
)
SELECT my_column->'receiptResult'->>'notes' FROM sample;
As you can see, -> operator returns value as a JSONB and ->> operator returns as a text.
More info here.
If I have a jsonb column called value with fields such as:
{"id": "5e367554-bf4e-4057-8089-a3a43c9470c0",
"tags": ["principal", "reversal", "interest"],,, etc}
how would I find all the records containing given tags, e.g:
if given: ["reversal", "interest"]
it should find all records with either "reversal" or "interest" or both.
My experimentation got me to this abomination so far:
select value from account_balance_updated
where value #> '{}' :: jsonb and value->>'tags' LIKE '%"principal"%';
of course this is completely wrong and inefficient
Assuming you are using PG 9.4+, you can use the jsonb_array_elements() function:
SELECT DISTINCT abu.*
FROM account_balance_updated abu,
jsonb_array_elements(abu.value->'tags') t
WHERE t.value <# '["reversal", "interest"]'::jsonb;
As it turned out you can use cool jsonb operators described here:
https://www.postgresql.org/docs/9.5/static/functions-json.html
so original query doesn't have to change much:
select value from account_balance_updated
where value #> '{}' :: jsonb and value->'tags' ?| array['reversal', 'interest'];
in my case I also needed to escape the ? (??|) because I am using so called "prepared statement" where you pass query string and parameters to jdbc and question marks are like placeholders for params:
https://docs.oracle.com/javase/tutorial/jdbc/basics/prepared.html
I have a table with an HSTORE column 'ext', where the value is an int4range. An example:
"p1"=>"[10, 18]", "p2"=>"[24, 32]", "p3"=>"[29, 32]", "p4"=>"[18, 19]"
However, when I try to create an expression index on this, I get an error:
CREATE INDEX ix_test3_p1
ON test3
USING gist
(((ext -> 'p1'::text)::int4range));
ERROR: data type text has no default operator class for access method
"gist" SQL state: 42704 Hint: You must specify an operator class for
the index or define a default operator class for the data type.
How do I create the operator for this?
NOTE
Each record may have its own unique set of keys. Each key represents an attribute, and the values the value range. So not all records will have "p1". Consider this an EAV model in hstore.
I don't get that error - I get "functions in index expression must be marked IMMUTABLE"
CREATE TABLE ht (ext hstore);
INSERT INTO ht VALUES ('p1=>"[10,18]"'), ('p1=>"[99,99]"');
CREATE INDEX ht_test_idx ON ht USING GIST ( ((ext->'p1'::text)::int4range) );
ERROR: functions in index expression must be marked IMMUTABLE
CREATE FUNCTION foo(hstore) RETURNS int4range LANGUAGE SQL AS $$ SELECT ($1->'p1')::int4range; $$ IMMUTABLE;
CREATE INDEX ht_test_idx ON ht USING GIST ( foo(ext) );
SET enable_seq_scan=false;
EXPLAIN SELECT * FROM ht WHERE foo(ext) = '[10,19)';
QUERY PLAN
-----------------------------------------------------------------------
Index Scan using ht_test_idx on ht (cost=0.25..8.52 rows=1 width=32)
Index Cond: (foo(ext) = '[10,19)'::int4range)
I'm guessing the cast isn't immutable because you can change the default format of the range from inclusive...exclusive "[...)" to something else. You presumably won't be doing that though.
Obviously you'll want your real function to deal with things like missing "p1" entries, badly formed range values etc.