Add guide on debugging memory issues

docs/en/guides/developer/debugging-memory-issues.md

@@ -0,0 +1,61 @@
+---
+slug: /en/guides/developer/debugging-memory-issues
+sidebar_label: Debugging Memory Issues
+sidebar_position: 1
+description: Queries to help you debug memory issues.
+---
+
+# Debugging memory issues
+
+When encountering memory issues, it is helpful to know what queries and resources are consuming a significant amount of memory. Below are queries that can help find which queries, databases, and tables can be optimized:
+
+**List queries by peak memory usage**
+
+```sql
+SELECT
+    initial_query_id,
+    query,
+    elapsed,
+    formatReadableSize(memory_usage),
+    formatReadableSize(peak_memory_usage),
+FROM system.processes
+ORDER BY peak_memory_usage DESC
+LIMIT 100;
+```
+
+**List metrics based on total memory usage**
+
+```sql
+SELECT
+    metric, description, formatReadableSize(value) size
+FROM
+    system.asynchronous_metrics
+WHERE
+    metric like '%Cach%'
+    or metric like '%Mem%'
+order by
+    value desc;
+```
+
+**List databases by current memory usage**
+
+```sql
+SELECT
+    database,
+    name,
+    formatReadableSize(total_bytes)
+FROM system.tables
+WHERE engine IN ('Memory','Set','Join');
+```
+
+**List merges by current memory usage**
+
+```sql
+SELECT formatReadableSize(sum(memory_usage)) FROM system.merges;
+```
+
+**List processes by current memory usage**
+
+```sql
+SELECT formatReadableSize(sum(memory_usage)) FROM system.processes;
+```

sidebars.js

@@ -45,6 +45,7 @@ const sidebars = {
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             'en/guides/developer/ttl',
             'en/guides/developer/deduplication',
+            'en/guides/developer/debugging-memory-issues',
             'en/sql-reference/dictionaries/index',
             'en/guides/developer/lightweight-update',
             'en/guides/developer/lightweight-delete',