Indexing JSONB with GIN in PostgreSQL - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a GIN index on the JSONB column named 'data'.

PostgreSQL

CREATE INDEX idx_data ON my_table USING [1] (data);

Drag options to blanks, or click blank then click option'

Abtree

Bgin

Chash

Dgist

Attempts:

3 left

💡 Hint

Common Mistakes

Using btree index which does not support JSONB efficiently.

Using hash index which is not suitable for JSONB.

Using gist index which is less common for JSONB.

The GIN index type is used for indexing JSONB columns efficiently in PostgreSQL.

2fill in blank

medium

Complete the code to create a GIN index on the 'info' JSONB column with the jsonb_path_ops operator class.

PostgreSQL

CREATE INDEX idx_info ON users USING gin (info [1]);

Drag options to blanks, or click blank then click option'

Ajsonb_path_ops

Bjsonb_ops

Cjson_ops

Djson_path_ops

Attempts:

3 left

💡 Hint

Common Mistakes

Using jsonb_ops which is the default but larger index.

Using json_ops which is invalid for JSONB.

Using json_path_ops which is not a valid operator class.

The jsonb_path_ops operator class creates a smaller and faster GIN index for existence queries on JSONB.

3fill in blank

hard

Fix the error in the index creation statement to correctly use GIN on the JSONB column 'attributes'.

PostgreSQL

CREATE INDEX idx_attr ON products USING gin (attributes [1]);

Drag options to blanks, or click blank then click option'

Ajsonb_ops

Bjson_ops

Cjsonb_path_ops

Djson_path_ops

Attempts:

3 left

💡 Hint

Common Mistakes

Using json_ops which is for JSON, not JSONB.

Using json_path_ops which is invalid.

Using jsonb_path_ops which is valid but not the default.

The correct operator class for a general GIN index on JSONB is jsonb_ops. The others are invalid or for JSON, not JSONB.

4fill in blank

hard

Fill both blanks to create a GIN index on the JSONB column 'details' using the default operator class.

PostgreSQL

CREATE INDEX idx_details ON orders USING [1] (details [2]);

Drag options to blanks, or click blank then click option'

Agin

Bbtree

Cjsonb_ops

Dhash

Attempts:

3 left

💡 Hint

Common Mistakes

Using btree index type which is invalid for JSONB.

Using hash index type which is not supported for JSONB.

Using jsonb_path_ops instead of jsonb_ops for default.

The index type must be gin and the operator class for JSONB default is jsonb_ops.

5fill in blank

hard

Fill all three blanks to create a GIN index on the JSONB column 'config' with the jsonb_path_ops operator class and a custom index name.

PostgreSQL

CREATE INDEX [1] ON settings USING [2] (config [3]);

Drag options to blanks, or click blank then click option'

Aidx_config_gin

Bgin

Cjsonb_path_ops

Dbtree

Attempts:

3 left

💡 Hint

Common Mistakes

Using btree index type which is invalid for JSONB.

Using jsonb_ops instead of jsonb_path_ops for optimized queries.

Not providing a custom index name.

The index name can be custom like idx_config_gin. The index type is gin and the operator class for optimized JSONB path queries is jsonb_path_ops.

Practice

1. What is the main purpose of creating a GIN index on a JSONB column in PostgreSQL?

easy

A. To convert JSONB data into plain text for easier reading

B. To compress the JSONB data to save disk space

C. To automatically backup JSONB data to another table

D. To speed up queries that search for specific keys or values inside the JSONB data

Solution

1. Step 1: Understand GIN index purpose

   GIN indexes are designed to speed up searches inside complex data types like JSONB by indexing keys and values.

2. Step 2: Identify the benefit for JSONB queries

   Queries using operators like @> that check for existence of keys or values run faster with GIN indexes.

3. Final Answer:

   To speed up queries that search for specific keys or values inside the JSONB data -> Option D

4. Quick Check:

   GIN index = faster JSONB key/value search [OK]

Hint: GIN indexes speed up JSONB key/value searches [OK]

Common Mistakes:

• Thinking GIN compresses JSONB data
• Confusing GIN with backup or conversion tools
• Assuming GIN indexes speed up all query types

2. Which of the following is the correct syntax to create a GIN index on a JSONB column named data in a table items?

easy

A. CREATE INDEX idx_data ON items USING GIN (data);

B. CREATE INDEX idx_data ON items USING BTREE (data);

C. CREATE INDEX idx_data ON items USING GIN (data (jsonb_path_ops));

D. CREATE INDEX idx_data ON items USING HASH (data);

Solution

1. Step 1: Recall correct GIN index syntax

   The standard way to create a GIN index on a JSONB column is: CREATE INDEX index_name ON table_name USING GIN (column_name);

2. Step 2: Check options for correctness

   CREATE INDEX idx_data ON items USING GIN (data); matches the correct syntax. CREATE INDEX idx_data ON items USING BTREE (data); uses BTREE which is not suitable for JSONB. CREATE INDEX idx_data ON items USING GIN (data (jsonb_path_ops)); has incorrect syntax (extra parentheses around jsonb_path_ops). CREATE INDEX idx_data ON items USING HASH (data); uses HASH which is not valid for JSONB indexing.

3. Final Answer:

   CREATE INDEX idx_data ON items USING GIN (data); -> Option A

4. Quick Check:

   Correct GIN index syntax = CREATE INDEX idx_data ON items USING GIN (data); [OK]

Hint: Use USING GIN with column name in parentheses [OK]

Common Mistakes:

• Using BTREE or HASH instead of GIN
• Incorrect syntax with extra keywords
• Missing parentheses around column name

3. Given a table products with a JSONB column attributes and a GIN index on it, what will this query return?

SELECT * FROM products WHERE attributes @> '{"color": "red"}';

medium

A. All rows where the JSONB column contains the key "color" with value "red"

B. All rows where the JSONB column contains any key named "color"

C. All rows where the JSONB column contains the value "red" anywhere

D. Syntax error due to incorrect JSON format

Solution

1. Step 1: Understand the @> operator

   The @> operator checks if the left JSONB contains the right JSONB as a subset, meaning the key-value pair must exist exactly.

2. Step 2: Analyze the query condition

   The condition attributes @> '{"color": "red"}' means the JSONB column must have a key "color" with value "red".

3. Final Answer:

   All rows where the JSONB column contains the key "color" with value "red" -> Option A

4. Quick Check:

   @> means contains key-value pair exactly [OK]

Hint: Use @> to find exact key-value pairs in JSONB [OK]

Common Mistakes:

• Thinking @> matches only keys, not values
• Assuming it matches any occurrence of value
• Confusing JSON syntax causing errors

4. You created a GIN index on a JSONB column but your queries are still slow. What is the most likely cause?

medium

A. The GIN index does not support JSONB data types

B. The index was created without specifying the JSONB column

C. The queries are not using the @> operator

D. The table has no rows

Solution

1. Step 1: Understand when GIN index helps

   GIN indexes on JSONB columns speed up queries that use operators like @> which check for containment.

2. Step 2: Identify why queries remain slow

   If queries do not use @> or other supported operators, the index won't be used, causing slow performance.

3. Final Answer:

   The queries are not using the @> operator -> Option C

4. Quick Check:

   GIN index helps only with supported operators [OK]

Hint: Use @> operator to leverage GIN index speedup [OK]

Common Mistakes:

• Assuming GIN indexes speed up all JSONB queries
• Not verifying query operator usage
• Thinking GIN index doesn't support JSONB

5. You want to create a GIN index on a JSONB column info in table users to optimize queries checking for existence of specific keys only, ignoring values. Which index operator class should you use?

hard

A. jsonb_ops

B. jsonb_path_ops

C. btree_gin

D. hash_ops

Solution

1. Step 1: Understand GIN operator classes for JSONB

   PostgreSQL provides two main operator classes for JSONB GIN indexes: jsonb_ops (default) indexes keys and values, and jsonb_path_ops indexes only keys for existence queries.

2. Step 2: Choose operator class for key existence queries

   Since the goal is to optimize queries checking for key existence only, jsonb_path_ops is the best choice as it creates a smaller, faster index for this purpose.

3. Final Answer:

   jsonb_path_ops -> Option B

4. Quick Check:

   Key-only queries use jsonb_path_ops [OK]

Hint: Use jsonb_path_ops for key-existence queries [OK]

Common Mistakes:

• Using default jsonb_ops which indexes values too
• Choosing unrelated operator classes like btree_gin
• Confusing hash_ops with GIN operator classes