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I have a table with jsonb field in table.
CREATE TABLE data.items ( id serial NOT NULL, datab jsonb ) How to get size of this field in a query like this:
select id, size(datab) from data.items 
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JSONB and IndexesPostgreSQL can use indexes for the text results as compare operands. GIN index can be used by the GIN JSONB operator class.
Speed. Because JSONB stores data in a binary format, queries process significantly faster. Storing data in binary form allows Postgres to access a particular JSON key-value pair without reading the entire JSON record.
PostgreSQL has two native operators -> and ->> to query JSON documents. The first operator -> returns a JSON object, while the operator ->> returns text. These operators work on both JSON as well as JSONB columns. There are additional operators available for JSONB columns.
JSONB stands for “JSON Binary” or “JSON better” depending on whom you ask. It is a decomposed binary format to store JSON. JSONB supports indexing the JSON data, and is very efficient at parsing and querying the JSON data. In most cases, when you work with JSON in PostgreSQL, you should be using JSONB.
The size limit of a json field is 1GB (source: this StackOverflow answer): json is the same as a text datatype but with JSON validation. The text datatype's maximum size is 1GB. I ran some experiments with inserting json of varying sizes into a table in Postgres.
The data type JSON and JSONB, as defined by the PostgreSQL documentation, are almost identical; the key difference is that JSON data is stored as an exact copy of the JSON input text, whereas JSONB stores data in a decomposed binary form; that is, not as an ASCII/UTF-8 string, but as binary code. More efficiency. Significantly faster to process.
Another important consideration for storage is how JSONB interacts with TOAST (The Oversize Attribute Storage Technique). Typically, when the size of your column exceeds the TOAST_TUPLE_THRESHOLD (2kb default), PostgreSQL will attempt to compress the data and fit in 2kb. If that doesn't work, the data is moved to out-of-line storage.
I ran some experiments with inserting json of varying sizes into a table in Postgres. Taking pg_sizeof of rows here seems to indicate that Postgres does compression of the json data.
For the number of bytes used to store:
select id, pg_column_size(datab) from data.items;
For the number of elements on the jsonb object:
select id, jsonb_array_length(datab) from data.items;
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