UNWIND Clause - List Processing in GQL | Tags

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It’s essential for bulk data loading, transformations, and working with collection properties. <h3 id="basic-syntax" class="position-relative d-flex align-items-center group"> Basic Syntax <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="basic-syntax" aria-haspopup="dialog" aria-label="Share link: Basic Syntax"> Share link </button> </h3>UNWIND expands each list element into a separate row: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">UNWIND [1, 2, 3, 4, 5] AS number RETURN number; -- Returns: -- number -- 1 -- 2 -- 3 -- 4 -- 5 </code></pre></div> <h3 id="batch-insert-operations" class="position-relative d-flex align-items-center group"> Batch Insert Operations <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="batch-insert-operations" aria-haspopup="dialog" aria-label="Share link: Batch Insert Operations"> Share link </button> </h3>UNWIND enables efficient bulk inserts with a single query: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Insert multiple users in one query UNWIND $users AS user CREATE (u:User { name: user.name, email: user.email, created_at: datetime() }); </code></pre></div>Python client usage: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python">users = [ {'name': 'Alice', 'email': '[email protected]'}, {'name': 'Bob', 'email': '[email protected]'}, {'name': 'Carol', 'email': '[email protected]'}, ] await conn.execute(""" UNWIND $users AS user CREATE (u:User {name: user.name, email: user.email}) """, {'users': users}) </code></pre></div> <h3 id="processing-collection-properties" class="position-relative d-flex align-items-center group"> Processing Collection Properties <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="processing-collection-properties" aria-haspopup="dialog" aria-label="Share link: Processing Collection Properties"> Share link </button> </h3>UNWIND works with properties that contain lists: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Expand tags from a node property MATCH (article:Article {id: $article_id}) UNWIND article.tags AS tag RETURN DISTINCT tag; -- Create relationships from a list property MATCH (user:User {id: $user_id}) UNWIND user.interests AS interest MERGE (t:Topic {name: interest}) CREATE (user)-[:INTERESTED_IN]->(t); </code></pre></div> <h3 id="combining-unwind-with-other-clauses" class="position-relative d-flex align-items-center group"> Combining UNWIND with Other Clauses <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="combining-unwind-with-other-clauses" aria-haspopup="dialog" aria-label="Share link: Combining UNWIND with Other Clauses"> Share link </button> </h3>UNWIND with MATCH: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Find users by a list of IDs UNWIND $user_ids AS id MATCH (u:User {id: id}) RETURN u.name, u.email; </code></pre></div>UNWIND with aggregation: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Count occurrences in a list UNWIND ['a', 'b', 'a', 'c', 'a', 'b'] AS item RETURN item, count(*) AS occurrences ORDER BY occurrences DESC; </code></pre></div>Nested UNWIND: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Process nested lists UNWIND $orders AS order UNWIND order.items AS item CREATE (o:Order {id: order.id})-[:CONTAINS]->(i:Item {sku: item.sku}); </code></pre></div> <h3 id="unwind-with-null-and-empty-lists" class="position-relative d-flex align-items-center group"> UNWIND with NULL and Empty Lists <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="unwind-with-null-and-empty-lists" aria-haspopup="dialog" aria-label="Share link: UNWIND with NULL and Empty Lists"> Share link </button> </h3>Empty list behavior: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Empty list produces no rows UNWIND [] AS x RETURN x; -- (no results) </code></pre></div>Preserving rows with empty lists: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Use CASE to handle empty lists MATCH (u:User) WITH u, CASE WHEN size(u.tags) = 0 THEN [null] ELSE u.tags END AS tags UNWIND tags AS tag RETURN u.name, tag; </code></pre></div>NULL in lists: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- NULL elements are preserved UNWIND [1, null, 3] AS x RETURN x; -- Returns: 1, null, 3 </code></pre></div> <h3 id="performance-considerations" class="position-relative d-flex align-items-center group"> Performance Considerations <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="performance-considerations" aria-haspopup="dialog" aria-label="Share link: Performance Considerations"> Share link </button> </h3>Batch size: For large datasets, consider chunking: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-python" data-lang="python">BATCH_SIZE = 1000 for i in range(0, len(items), BATCH_SIZE): batch = items[i:i + BATCH_SIZE] await conn.execute(""" UNWIND $batch AS item CREATE (n:Node {data: item}) """, {'batch': batch}) </code></pre></div>Index usage: UNWIND with MATCH benefits from indexes on matched properties. <h3 id="common-patterns" class="position-relative d-flex align-items-center group"> Common Patterns <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="common-patterns" aria-haspopup="dialog" aria-label="Share link: Common Patterns"> Share link </button> </h3>De-duplication: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">UNWIND [1, 2, 2, 3, 3, 3] AS num RETURN DISTINCT num; </code></pre></div>List to relationships: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">MATCH (user:User {id: $user_id}) UNWIND $friend_ids AS friend_id MATCH (friend:User {id: friend_id}) CREATE (user)-[:FRIENDS_WITH]->(friend); </code></pre></div>Generating sequences: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">UNWIND range(1, 100) AS i CREATE (n:Node {index: i}); </code></pre></div> <h3 id="related-topics" class="position-relative d-flex align-items-center group"> Related Topics <button type="button" class="h-share btn btn-link p-0 text-decoration-none link-secondary opacity-50 hover-opacity-100 transition-all ms-1" data-share-target="related-topics" aria-haspopup="dialog" aria-label="Share link: Related Topics"> Share link </button> </h3><ul> <li><a href="/tags/etl/" >Batch Operations</a> </li> <li><a href="/tags/pattern-matching/" >Pattern Matching</a> </li> <li><a href="/tags/merge/" >MERGE Clause</a> </li> <li><a href="/tags/performance/" >Performance</a> </li> <li><a href="/tags/gql-reference/" >GQL Reference</a> </li> </ul>

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UNWIND Clause - List Processing in GQL

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