Query Optimization | Geode Database

<h2 id="query-optimization" class="position-relative d-flex align-items-center group"> Query Optimization <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="query-optimization" aria-haspopup="dialog" aria-label="Share link: Query Optimization"> Share link </button> </h2><div id="headingShareModal" class="heading-share-modal" role="dialog" aria-modal="true" aria-labelledby="headingShareTitle" hidden> <div class="hsm-dialog" role="document"> <div class="hsm-header"> <h2 id="headingShareTitle" class="h6 mb-0 fw-bold">Share this section</h2> <button type="button" class="hsm-close" aria-label="Close"> </button> </div> <div class="hsm-body"> <label for="headingShareInput" class="form-label small text-muted mb-1 text-uppercase fw-bold" style="font-size: 0.7rem; letter-spacing: 0.5px;">Permalink</label> <div class="input-group mb-4 hsm-url-group"> <input id="headingShareInput" type="text" class="form-control font-monospace" readonly aria-readonly="true" style="font-size: 0.85rem;" /> <button class="btn btn-primary hsm-copy" type="button" aria-label="Copy" title="Copy"> </button> </div> <div class="small fw-bold mb-2 text-muted text-uppercase" style="font-size: 0.7rem; 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} if(copyBtn && (e.target===copyBtn || (e.target.closest && e.target.closest('.hsm-copy')))) { e.preventDefault(); copyCurrent(); } }); document.addEventListener('keydown', e=>{ if(e.key==='Escape' && isOpen()) closeModal(); }); function trapFocus(){ if(trapBound) return; trapBound=true; modal.addEventListener('keydown', f=>{ if(f.key==='Tab' && isOpen()){ const focusable=[...modal.querySelectorAll('a[href],button,input,textarea,select,[tabindex]:not([tabindex="-1"])')].filter(el=>!el.hasAttribute('disabled')); if(!focusable.length) return; const first=focusable[0]; const last=focusable[focusable.length-1]; if(f.shiftKey && document.activeElement===first){ f.preventDefault(); last.focus(); } else if(!f.shiftKey && document.activeElement===last){ f.preventDefault(); first.focus(); } } }); } if(closeBtn) closeBtn.addEventListener('click', e=>{ e.preventDefault(); closeModal(); }); })(); </script>Geode implements a sophisticated cost-based query optimizer (CBO) that automatically selects efficient execution plans based on data statistics, index availability, and query patterns. <h3 id="overview" class="position-relative d-flex align-items-center group"> Overview <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="overview" aria-haspopup="dialog" aria-label="Share link: Overview"> Share link </button> </h3>The optimizer transforms logical query plans into optimized physical execution plans: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback">┌─────────────────┐ ┌─────────────────┐ ┌─────────────────┐ │ Logical Plan │────▶│ Optimizer │────▶│ Physical Plan │ │ │ │ │ │ │ │ - What to do │ │ - Statistics │ │ - How to do it │ │ - Declarative │ │ - Cost model │ │ - Imperative │ └─────────────────┘ │ - Index info │ └─────────────────┘ └─────────────────┘ </code></pre></div> <h3 id="cost-model" class="position-relative d-flex align-items-center group"> Cost Model <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="cost-model" aria-haspopup="dialog" aria-label="Share link: Cost Model"> Share link </button> </h3> <h4 id="cost-components" class="position-relative d-flex align-items-center group"> Cost Components <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="cost-components" aria-haspopup="dialog" aria-label="Share link: Cost Components"> Share link </button> </h4>The optimizer considers three primary cost factors: <ol> <li>I/O Cost: Disk reads and writes</li> <li>CPU Cost: Computation overhead</li> <li>Memory Cost: Buffer pool utilization</li> </ol> <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-zig" data-lang="zig">pub const Cost = struct { io_cost: f64, // Estimated page reads cpu_cost: f64, // Estimated operations memory_cost: f64, // Estimated memory usage pub fn total(self: Cost) f64 { return self.io_cost * IO_WEIGHT + self.cpu_cost * CPU_WEIGHT + self.memory_cost * MEMORY_WEIGHT; } }; </code></pre></div> <h4 id="cost-estimation" class="position-relative d-flex align-items-center group"> Cost Estimation <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="cost-estimation" aria-haspopup="dialog" aria-label="Share link: Cost Estimation"> Share link </button> </h4><table> <thead> <tr> <th>Operation</th> <th>Cost Formula</th> </tr> </thead> <tbody> <tr> <td>Full Scan</td> <td><code>pages * io_cost + rows * cpu_cost</code></td> </tr> <tr> <td>Index Seek</td> <td><code>log(n) * io_cost + selectivity * rows * cpu_cost</code></td> </tr> <tr> <td>Hash Join</td> <td><code>build_cost + probe_cost + memory_cost</code></td> </tr> <tr> <td>Sort</td> <td><code>n * log(n) * cpu_cost + spill_io_cost</code></td> </tr> </tbody> </table> <h3 id="optimization-strategies" class="position-relative d-flex align-items-center group"> Optimization Strategies <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="optimization-strategies" aria-haspopup="dialog" aria-label="Share link: Optimization Strategies"> Share link </button> </h3> <h4 id="1-predicate-pushdown" class="position-relative d-flex align-items-center group"> 1. Predicate Pushdown <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="1-predicate-pushdown" aria-haspopup="dialog" aria-label="Share link: 1. Predicate Pushdown"> Share link </button> </h4>Move filters closer to data sources to reduce intermediate result sizes: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback">Before: After: Filter (age > 30) Expand (KNOWS) │ │ └─▶ Expand (KNOWS) └─▶ Filter (age > 30) │ │ └─▶ Scan (Person) └─▶ Scan (Person) </code></pre></div>Example: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Original query MATCH (p:Person)-[:KNOWS]->(f:Person) WHERE p.age > 30 RETURN f.name -- Optimized: Filter pushed before expansion </code></pre></div> <h4 id="2-index-selection" class="position-relative d-flex align-items-center group"> 2. Index Selection <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="2-index-selection" aria-haspopup="dialog" aria-label="Share link: 2. Index Selection"> Share link </button> </h4>The optimizer automatically selects the most efficient index: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-zig" data-lang="zig">fn selectBestIndex( scan: *ScanOperator, available_indexes: []Index, stats: *Statistics ) ?Index { var best_index: ?Index = null; var best_cost = std.math.inf(f64); for (available_indexes) |index| { if (!index.covers(scan.predicates)) continue; const selectivity = estimateSelectivity(scan.predicates, index, stats); const cost = estimateIndexCost(index, selectivity, stats); if (cost < best_cost) { best_cost = cost; best_index = index; } } return best_index; } </code></pre></div>Index Selection Rules: <ul> <li>Use equality indexes for exact matches</li> <li>Use range indexes for comparison predicates</li> <li>Consider covering indexes to avoid lookups</li> <li>Prefer composite indexes matching multiple predicates</li> </ul> <h4 id="3-join-ordering" class="position-relative d-flex align-items-center group"> 3. Join Ordering <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="3-join-ordering" aria-haspopup="dialog" aria-label="Share link: 3. Join Ordering"> Share link </button> </h4>Optimal join order minimizes intermediate result sizes: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback">Poor Order: Optimal Order: Join (1M × 10K = 10B) Join (10 × 10K = 100K) │ │ ├─▶ Scan A (1M rows) ├─▶ Filter (10 rows) │ │ │ └─▶ Scan B (10K rows) │ └─▶ Scan A │ └─▶ Scan B (10K rows) </code></pre></div>Join Order Algorithm: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-zig" data-lang="zig">fn optimizeJoinOrder(joins: []Join, stats: *Statistics) []Join { // Use dynamic programming for small join counts if (joins.len <= 6) { return dpJoinOrdering(joins, stats); } // Use greedy heuristic for larger join counts return greedyJoinOrdering(joins, stats); } </code></pre></div> <h4 id="4-join-type-selection" class="position-relative d-flex align-items-center group"> 4. Join Type Selection <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="4-join-type-selection" aria-haspopup="dialog" aria-label="Share link: 4. Join Type Selection"> Share link </button> </h4>Choose the optimal join algorithm based on input sizes: <table> <thead> <tr> <th>Join Type</th> <th>Best For</th> <th>Cost</th> </tr> </thead> <tbody> <tr> <td>Nested Loop</td> <td>Small inner, indexed</td> <td><code>O(n)</code> with index</td> </tr> <tr> <td>Hash Join</td> <td>Equality joins, fits memory</td> <td><code>O(n + m)</code></td> </tr> <tr> <td>Merge Join</td> <td>Pre-sorted inputs</td> <td><code>O(n + m)</code></td> </tr> </tbody> </table> <h4 id="5-aggregation-pushdown" class="position-relative d-flex align-items-center group"> 5. Aggregation Pushdown <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="5-aggregation-pushdown" aria-haspopup="dialog" aria-label="Share link: 5. Aggregation Pushdown"> Share link </button> </h4>Push aggregations to reduce data movement: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback">Before: After: Aggregate (COUNT) Aggregate (SUM of counts) │ │ └─▶ Union All └─▶ Union All │ │ ├─▶ Shard 1 ├─▶ Local COUNT (Shard 1) └─▶ Shard 2 └─▶ Local COUNT (Shard 2) </code></pre></div> <h3 id="statistics-collection" class="position-relative d-flex align-items-center group"> Statistics Collection <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="statistics-collection" aria-haspopup="dialog" aria-label="Share link: Statistics Collection"> Share link </button> </h3> <h4 id="automatic-statistics" class="position-relative d-flex align-items-center group"> Automatic Statistics <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="automatic-statistics" aria-haspopup="dialog" aria-label="Share link: Automatic Statistics"> Share link </button> </h4>Geode automatically maintains statistics for optimization: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-yaml" data-lang="yaml">statistics: auto_update: true update_threshold: 10000 # Update after N modifications sample_size: 1000 # Rows sampled for histograms </code></pre></div> <h4 id="statistics-types" class="position-relative d-flex align-items-center group"> Statistics Types <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="statistics-types" aria-haspopup="dialog" aria-label="Share link: Statistics Types"> Share link </button> </h4><table> <thead> <tr> <th>Statistic</th> <th>Description</th> </tr> </thead> <tbody> <tr> <td>Cardinality</td> <td>Number of rows per label/type</td> </tr> <tr> <td>Selectivity</td> <td>Predicate filtering ratio</td> </tr> <tr> <td>Histogram</td> <td>Value distribution for range estimation</td> </tr> <tr> <td>Distinct Count</td> <td>Number of unique values</td> </tr> </tbody> </table> <h4 id="manual-statistics-update" class="position-relative d-flex align-items-center group"> Manual Statistics Update <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="manual-statistics-update" aria-haspopup="dialog" aria-label="Share link: Manual Statistics Update"> Share link </button> </h4><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Update all statistics CALL db.stats.update() -- Update statistics for specific label CALL db.stats.update('Person') -- View current statistics CALL db.stats.show() </code></pre></div> <h3 id="adaptive-query-execution" class="position-relative d-flex align-items-center group"> Adaptive Query Execution <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="adaptive-query-execution" aria-haspopup="dialog" aria-label="Share link: Adaptive Query Execution"> Share link </button> </h3>Geode can adjust execution plans at runtime: <h4 id="runtime-statistics" class="position-relative d-flex align-items-center group"> Runtime Statistics <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="runtime-statistics" aria-haspopup="dialog" aria-label="Share link: Runtime Statistics"> Share link </button> </h4><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-zig" data-lang="zig">pub const RuntimeStats = struct { rows_processed: u64, actual_selectivity: f64, memory_used: usize, pub fn shouldReplan(self: RuntimeStats, estimated: Cost) bool { const actual_cost = self.computeActualCost(); return actual_cost > estimated.total() * REPLAN_THRESHOLD; } }; </code></pre></div> <h4 id="mid-query-optimization" class="position-relative d-flex align-items-center group"> Mid-Query Optimization <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="mid-query-optimization" aria-haspopup="dialog" aria-label="Share link: Mid-Query Optimization"> Share link </button> </h4>When actual cardinalities differ significantly from estimates: <ol> <li>Pause execution</li> <li>Re-optimize with actual statistics</li> <li>Resume with new plan</li> </ol> <h3 id="query-hints" class="position-relative d-flex align-items-center group"> Query Hints <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="query-hints" aria-haspopup="dialog" aria-label="Share link: Query Hints"> Share link </button> </h3>Override optimizer decisions when needed: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Force specific index MATCH (p:Person) USING INDEX p:Person(email) WHERE p.email = 'alice@example.com' RETURN p -- Force join order MATCH (a:Account)-[:OWNS]->(t:Transaction) USING JOIN ON a WHERE a.balance > 10000 RETURN t </code></pre></div> <h3 id="explain-and-profile" class="position-relative d-flex align-items-center group"> EXPLAIN and PROFILE <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="explain-and-profile" aria-haspopup="dialog" aria-label="Share link: EXPLAIN and PROFILE"> Share link </button> </h3> <h4 id="explain" class="position-relative d-flex align-items-center group"> EXPLAIN <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="explain" aria-haspopup="dialog" aria-label="Share link: EXPLAIN"> Share link </button> </h4>View the query plan without execution: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">EXPLAIN MATCH (p:Person)-[:KNOWS]->(f:Person) WHERE p.age > 30 RETURN f.name </code></pre></div>Output: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback">| plan | estimated_rows | |-------------------------------|----------------| | Project (f.name) | 1000 | | Expand (KNOWS, OUTGOING) | 1000 | | Filter (p.age > 30) | 500 | | IndexSeek (Person.age) | 500 | </code></pre></div> <h4 id="profile" class="position-relative d-flex align-items-center group"> PROFILE <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="profile" aria-haspopup="dialog" aria-label="Share link: PROFILE"> Share link </button> </h4>Execute and show actual statistics: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">PROFILE MATCH (p:Person)-[:KNOWS]->(f:Person) WHERE p.age > 30 RETURN f.name </code></pre></div>Output: <div class="highlight"><pre tabindex="0" class="chroma"><code class="language-fallback" data-lang="fallback">| plan | rows | db_hits | time_ms | |-------------------------------|-------|---------|---------| | Project (f.name) | 847 | 847 | 0.5 | | Expand (KNOWS, OUTGOING) | 847 | 1694 | 12.3 | | Filter (p.age > 30) | 423 | 423 | 1.2 | | IndexSeek (Person.age) | 423 | 846 | 3.1 | | Total | | 3810 | 17.1 | </code></pre></div> <h3 id="best-practices" class="position-relative d-flex align-items-center group"> Best Practices <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="best-practices" aria-haspopup="dialog" aria-label="Share link: Best Practices"> Share link </button> </h3> <h4 id="1-create-appropriate-indexes" class="position-relative d-flex align-items-center group"> 1. Create Appropriate Indexes <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="1-create-appropriate-indexes" aria-haspopup="dialog" aria-label="Share link: 1. Create Appropriate Indexes"> Share link </button> </h4><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Index frequently filtered properties CREATE INDEX ON :Person(email) CREATE INDEX ON :Person(age) -- Composite index for common predicates CREATE INDEX ON :Transaction(account_id, timestamp) </code></pre></div> <h4 id="2-write-selective-predicates-first" class="position-relative d-flex align-items-center group"> 2. Write Selective Predicates First <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="2-write-selective-predicates-first" aria-haspopup="dialog" aria-label="Share link: 2. Write Selective Predicates First"> Share link </button> </h4><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Good: Most selective predicate first MATCH (p:Person) WHERE p.email = 'alice@example.com' -- Unique AND p.age > 30 -- Less selective RETURN p -- The optimizer handles this, but it helps readability </code></pre></div> <h4 id="3-avoid-cartesian-products" class="position-relative d-flex align-items-center group"> 3. Avoid Cartesian Products <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="3-avoid-cartesian-products" aria-haspopup="dialog" aria-label="Share link: 3. Avoid Cartesian Products"> Share link </button> </h4><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Bad: Cartesian product MATCH (p:Person), (c:Company) RETURN p.name, c.name -- Good: Use relationships MATCH (p:Person)-[:WORKS_AT]->(c:Company) RETURN p.name, c.name </code></pre></div> <h4 id="4-use-limit-for-large-results" class="position-relative d-flex align-items-center group"> 4. Use LIMIT for Large Results <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="4-use-limit-for-large-results" aria-haspopup="dialog" aria-label="Share link: 4. Use LIMIT for Large Results"> Share link </button> </h4><div class="highlight"><pre tabindex="0" class="chroma"><code class="language-gql" data-lang="gql">-- Always limit result sets MATCH (p:Person) RETURN p ORDER BY p.name LIMIT 100 </code></pre></div> <h3 id="performance-tuning" class="position-relative d-flex align-items-center group"> Performance Tuning <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-tuning" aria-haspopup="dialog" aria-label="Share link: Performance Tuning"> Share link </button> </h3>See also: <ul> <li><a href="/docs/query/performance-tuning/" >Performance Tuning Guide</a> </li> <li><a href="/docs/tutorials/index-optimization/" >Index Optimization Tutorial</a> </li> </ul> <h3 id="next-steps" class="position-relative d-flex align-items-center group"> Next Steps <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="next-steps" aria-haspopup="dialog" aria-label="Share link: Next Steps"> Share link </button> </h3><ul> <li><a href="/docs/architecture/storage-engine/" >Storage Engine</a> - Understand data storage</li> <li><a href="/docs/architecture/distributed-systems/" >Distributed Systems</a> - Multi-node query execution</li> <li><a href="/docs/architecture/query-execution/" >Query Execution</a> - Execution pipeline details</li> </ul>