Collections Statistics

View statistics for all collections in a database simultaneously with a comprehensive table interface. Compare collection sizes, document counts, index usage, and storage efficiency across your entire database to identify optimization opportunities and monitor database-wide health.

Table Columns Explained

The collections table displays 8 columns of metrics for each collection in the database:

Column	Metric	Description
Collection	Collection name	Name of the collection with a colored status indicator (green=loaded, yellow=loading, red=error)
Documents	Total document count	Number of documents in the collection (stats.count), formatted with thousands separators
Storage Size	Compressed storage size	Allocated disk space including compression (stats.storageSize)
Data Size	Uncompressed data size	Total size of all documents before compression (stats.size)
Indexes	Number of indexes	Count of indexes defined on the collection (stats.nindexes), including the default _id index
Index Size	Total index storage	Combined size of all indexes on the collection (stats.totalIndexSize)
Avg Object Size	Average document size	Average size per document in the collection (stats.avgObjSize)
Efficiency	Storage efficiency	Percentage of storage actually in use with visual progress bar: (data size / storage size) × 100

Status Indicators

Each collection row displays a colored dot indicator showing the loading status:

• Green Dot - Statistics successfully loaded for this collection
• Yellow Dot (pulsing) - Statistics are currently loading for this collection
• Red Dot - Error loading statistics (check permissions or collection accessibility)

When statistics fail to load for a collection, the row displays "-" for all metric columns and shows the red error indicator.

Storage Efficiency Visualization

The Efficiency column includes both a visual progress bar and a percentage value:

Understanding the Efficiency Bar

• Gradient Color - Blue to green gradient indicates healthy efficiency
• Bar Length - Longer bar = higher efficiency (less wasted space)
• Percentage Value - Exact efficiency ratio displayed next to the bar
• 100% Efficiency - All allocated storage is being used (ideal)
• Low Efficiency - Indicates significant free space that could be reclaimed

Efficiency Thresholds

• 90-100% - Excellent: Minimal wasted space
• 70-90% - Good: Normal for active collections
• 50-70% - Fair: Monitor for potential optimization
• Below 50% - Poor: Consider running compact to reclaim space

Comparing Collections

Use the all-collections table to identify patterns and outliers across your database:

Key Comparisons

• Largest Collections - Sort by Storage Size or Data Size to find collections consuming the most disk space
• Most Documents - Sort by Documents column to find high-volume collections
• Index Overhead - Compare Index Size to Data Size; high ratios may indicate over-indexing
• Average Document Size - Identify collections with unusually large or small documents
• Low Efficiency - Find collections with wasted space that need maintenance

Identifying Optimization Opportunities

• Index Bloat - Collections where Index Size exceeds Data Size may have redundant indexes
• Large Documents - High Avg Object Size may indicate embedded documents that should be referenced instead
• Empty Collections - 0 documents but allocated storage suggests the collection can be dropped or compacted
• Fragmented Collections - Low efficiency after deletions indicates compaction needed

Footer Summary

The sticky footer at the bottom of the table displays summary information:

• Total Collections - Total number of collections in the database
• Loaded - Number of collections that successfully loaded statistics (shown in green)
• Loading Progress - Shows "Loaded: X / Y" to track loading progress

The footer remains visible as you scroll through the table, providing context about the overall status.

Double-Click Navigation

Double-click any collection row to open the detailed Collection Statistics view for that collection:

• A new tab opens showing the 4-tab detailed statistics interface (Overview, Indexes, Cache, Storage)
• The tab is named "Collection Stats - [collection name]"
• You can keep the all-collections view open in another tab for quick comparison
• Use this to drill down when you identify collections needing closer inspection

Tip: After identifying problematic collections in the overview table, double-click to analyze them in detail.

Auto-Refresh Feature

Enable the Auto-refresh checkbox in the top-right controls to monitor all collections in real-time:

• Refresh Interval - Statistics reload every 30 seconds (default)
• Parallel Loading - Statistics for all collections are fetched in parallel for faster updates
• Status Tracking - Each collection shows its loading status independently
• Error Resilience - If one collection fails, others continue loading successfully

Use Cases for Auto-Refresh

• Monitoring database growth during bulk imports across multiple collections
• Tracking storage changes after running maintenance operations
• Observing index build progress on multiple collections
• Watching efficiency metrics improve after running compact operations

Performance Note: Auto-refresh executes db.collection.stats() for each collection. For databases with many collections (50+), consider manual refresh instead.

Available Actions

Refresh Statistics

Click the Refresh button to reload statistics for all collections. This executes db.collection.stats() for each collection in parallel.

Enable Auto-Refresh

Check the Auto-refresh checkbox to automatically reload statistics every 30 seconds for continuous monitoring.

Open Collection Details

Double-click any collection row to open the detailed 4-tab Collection Statistics view for deeper analysis.

Sort by Column

Click column headers to sort the table by that metric (e.g., sort by Storage Size to find largest collections).

Pro Tips

1. Spot Check Regularly: Review the all-collections table weekly to identify collections growing rapidly or showing low efficiency.
2. Index Ratio Analysis: Calculate index-to-data ratio by comparing Index Size to Data Size. Ratios above 1.0 suggest reviewing your indexing strategy.
3. Find Fragmentation: Collections with low efficiency (below 70%) after deletions need compact to reclaim space. Schedule during maintenance windows.
4. Document Size Warnings: Very large average document sizes (>1MB) may indicate embedded documents that should be split into separate collections.
5. Capacity Planning: Export the table data and track growth trends over time to predict when you'll need additional storage capacity.
6. Quick Triage: Use the status indicators (colored dots) to quickly identify collections with loading errors that may have permission or accessibility issues.

Parallel Loading Performance

VisualLeaf optimizes the all-collections view by loading statistics in parallel:

How It Works

• Batch Requests - All collection stats are requested simultaneously using RxJS forkJoin
• Independent Loading - Each collection loads independently; one failure doesn't block others
• Progressive Display - Collections appear with yellow loading indicators, then update to green when loaded
• Error Isolation - Collections that fail to load show red indicators while others continue

Performance Considerations

• Small Databases (1-20 collections) - Loading is nearly instant
• Medium Databases (20-50 collections) - Loading takes 1-3 seconds
• Large Databases (50+ collections) - May take 5-10 seconds; consider disabling auto-refresh
• Server Impact - Each collection executes db.collection.stats(); minimal impact due to metadata reads

Understanding the Stats Commands

For each collection in the database, VisualLeaf executes:

// For each collection
db.collection.stats({ scale: 1 })

These commands are executed in parallel using efficient batching to minimize load time.

Performance Impact

• Read-Only Operation - No data modification, only metadata reads
• Brief Locks - Short read locks per collection; safe for production
• Cache Friendly - Stats are often served from WiredTiger's cache
• Parallel Execution - Multiple stats commands run concurrently

Related Features

• Database Statistics - View aggregate statistics for the entire database (all collections combined)
• Collection Statistics - Double-click a row to see detailed 4-tab statistics for a specific collection
• Index Management - Manage indexes on collections identified as having index overhead
• Collection Activity - Query and view documents in collections you identify
• Server Build Info - Check MongoDB version and WiredTiger configuration affecting stats

Troubleshooting

Red Status Indicators (Failed to Load)

If some collections show red dots and "-" for all metrics:

• Permission Issues - Verify your user has read permissions on all collections
• Views vs Collections - Views may not return standard stats; this is normal
• System Collections - Some system collections have restricted access
• Connection Issues - Temporary network issues may cause individual failures

Slow Loading

If the table takes a long time to load:

• Many Collections - Databases with 100+ collections naturally take longer
• Large Collections - Stats for very large collections take more time to calculate
• Server Load - High server load may slow stats calculations
• Network Latency - Remote connections have additional overhead

Unexpected Efficiency Values

If efficiency percentages seem incorrect:

• Recent Deletions - Efficiency drops after deletions; run compact to reclaim space
• Compression - WiredTiger compression can make efficiency exceed 100% (data size > storage size)
• Free Space Allocation - MongoDB pre-allocates space; normal for growing collections