to_tsquery for search terms in PostgreSQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Basic to_tsquery search output

Given a table documents with a text column content, what rows will match the query to_tsquery('cat & dog')?

PostgreSQL

SELECT id, content FROM documents WHERE to_tsvector(content) @@ to_tsquery('cat & dog');

A Rows where content contains 'cat' followed immediately by 'dog' with no words between

B Rows where content contains either 'cat' or 'dog', but not necessarily both

C Rows where content contains the exact phrase 'cat dog' in sequence

D Rows where content contains both 'cat' and 'dog' anywhere in the text

💡 Hint

The & operator means AND in to_tsquery syntax.

The & operator in to_tsquery means both terms must be present anywhere in the text. So only rows containing both 'cat' and 'dog' match.

❓ query_result

intermediate

Using OR operator in to_tsquery

What is the result of this query?
SELECT id FROM documents WHERE to_tsvector(content) @@ to_tsquery('cat | dog');

A Rows containing either 'cat' or 'dog' or both

B Rows containing both 'cat' and 'dog' only

C Rows containing the exact phrase 'cat dog'

D Rows containing neither 'cat' nor 'dog'

💡 Hint

The | operator means OR in to_tsquery syntax.

The | operator means either term can be present. So rows with 'cat', 'dog', or both will match.

📝 Syntax

advanced

Identify the syntax error in to_tsquery

Which option contains a syntax error when used inside to_tsquery()?

A 'cat & | dog'

B 'cat | dog'

C 'cat & dog'

D 'cat <-> dog'

💡 Hint

Check operator placement and usage rules.

The & and | operators cannot be adjacent without a term between them. Option A has '& |' which is invalid syntax.

❓ query_result

advanced

Phrase search with <-> operator

What does this query return?
SELECT id FROM documents WHERE to_tsvector(content) @@ to_tsquery('cat <-> dog');

A Rows where 'cat' and 'dog' appear separated by exactly one word

B Rows where 'cat' is immediately followed by 'dog' in the text

C Rows where 'cat' or 'dog' appear anywhere in the text

D Rows where 'cat' and 'dog' appear anywhere in the text, order doesn't matter

💡 Hint

The <-> operator means words are adjacent in order.

The <-> operator matches phrases where the first word is immediately followed by the second word.

🧠 Conceptual

expert

Understanding lexeme normalization in to_tsquery

Which statement about to_tsquery lexeme normalization is true?

A It ignores stop words but does not stem words

B It searches for exact word matches without any normalization

C It converts words to their root form (stemming) before searching

D It only matches words at the start of the text

💡 Hint

Think about how PostgreSQL handles word variations in full text search.

to_tsquery applies stemming to convert words to their root forms, so searches match different word forms.

Practice

1. What does the to_tsquery function do in PostgreSQL?

easy

A. It converts search terms into a format for full-text search queries.

B. It creates a new table for storing search terms.

C. It updates text columns with search keywords.

D. It deletes rows that match search terms.

Solution

1. Step 1: Understand the purpose of to_tsquery

   to_tsquery converts plain search words into a special query format that PostgreSQL can use for full-text searching.

2. Step 2: Compare options with the function's role

   Only It converts search terms into a format for full-text search queries. correctly describes this conversion role. Other options describe unrelated database actions.

3. Final Answer:

   It converts search terms into a format for full-text search queries. -> Option A

4. Quick Check:

   to_tsquery = converts search terms [OK]

Hint: Remember: to_tsquery prepares search words for text search [OK]

Common Mistakes:

• Thinking it creates or modifies tables
• Confusing it with data update or delete operations
• Assuming it returns raw text instead of a query format

2. Which of the following is the correct syntax to create a to_tsquery for searching the words 'cat' AND 'dog' using the explicit AND operator?

easy

A. to_tsquery('cat | dog')

B. to_tsquery('cat & dog')

C. to_tsquery('cat dog')

D. to_tsquery('cat && dog')

Solution

1. Step 1: Recall the AND operator in to_tsquery

   The AND operator is represented by & in to_tsquery syntax.

2. Step 2: Match the correct syntax

   to_tsquery('cat & dog') uses & correctly between 'cat' and 'dog'. to_tsquery('cat | dog') uses OR, C misses operator, and D uses invalid &&.

3. Final Answer:

   to_tsquery('cat & dog') -> Option B

4. Quick Check:

   AND = & in to_tsquery [OK]

Hint: Use & for AND, | for OR in to_tsquery strings [OK]

Common Mistakes:

• Using spaces without operators to mean AND
• Using double ampersands (&&) instead of single &
• Confusing OR (|) with AND (&)

3. Given the query:
SELECT to_tsquery('fast & !slow');
What is the expected output?

medium

A. 'fast' | !'slow'

B. Syntax error

C. 'fast' & !'slow'

D. 'fast slow'

Solution

1. Step 1: Understand the operators in the query

   The query uses AND (&) between 'fast' and NOT (!) 'slow'. This means search for 'fast' but exclude 'slow'.

2. Step 2: Check the output format of to_tsquery

   PostgreSQL returns the query as a string with words quoted and operators preserved. So output is 'fast' & !'slow'.

3. Final Answer:

   'fast' & !'slow' -> Option C

4. Quick Check:

   AND = & and NOT = ! in output [OK]

Hint: NOT is !, AND is & in to_tsquery output [OK]

Common Mistakes:

• Confusing OR (|) with AND (&)
• Expecting raw words without quotes
• Thinking the query causes syntax error

4. Identify the error in this query:
SELECT to_tsquery('apple & | orange');

medium

A. Syntax error due to consecutive operators & |

B. No error, valid query

C. Error because words must be uppercase

D. Error because to_tsquery needs two arguments

Solution

1. Step 1: Analyze the operator usage in the query string

   The string has & | operators consecutively without a word between them, which is invalid syntax.

2. Step 2: Confirm PostgreSQL behavior

   PostgreSQL will raise a syntax error because operators must separate valid search terms, not each other.

3. Final Answer:

   Syntax error due to consecutive operators & | -> Option A

4. Quick Check:

   Operators must separate words, not each other [OK]

Hint: Avoid placing operators consecutively without words [OK]

Common Mistakes:

• Assuming multiple operators in a row are allowed
• Thinking case of words matters
• Believing to_tsquery requires multiple arguments

5. You want to search for documents containing the word 'run' but not 'running'. Which to_tsquery expression correctly achieves this?

hard

A. to_tsquery('run ! running')

B. to_tsquery('run | !running')

C. to_tsquery('run & !run')

D. to_tsquery('run & !running')

Solution

1. Step 1: Understand the requirement

   You want documents that contain 'run' but exclude those that contain 'running'. This means AND 'run' and NOT 'running'.

2. Step 2: Choose the correct operator usage

   AND is & and NOT is !. to_tsquery('run & !running') uses these correctly. to_tsquery('run | !running') uses OR which is wrong. to_tsquery('run & !run') excludes 'run' itself. to_tsquery('run ! running') has invalid syntax (missing operator between 'run' and '!').

3. Final Answer:

   to_tsquery('run & !running') -> Option D

4. Quick Check:

   AND = & and NOT = ! for correct filtering [OK]

Hint: Use & for AND, ! for NOT to exclude terms [OK]

Common Mistakes:

• Using OR instead of AND for inclusion
• Excluding the main word accidentally
• Missing operators between words