---
title: "Query Metrics"
description: "Rank PostgreSQL and MongoDB queries by frequency and duration, read explain plans, analyze wait events and blocking, and see who runs each query."
section: "APM"
breadcrumb: "APM > Database Monitoring > Query Metrics"
canonical: "https://docs.middleware.io/features/apm/database-monitoring/query-metrics"
---
# Query Metrics

The **Query Metrics** tab groups executions of the same query together, so you can rank queries by how often they run and how long they take. PostgreSQL queries are grouped by **normalized query** text per instance. MongoDB operations are grouped by **query signature** per host.

Open it from **APM → Database → Query Metrics**, and select the engine in the **Overview** list.

![PostgreSQL Query Metrics with query count and average duration charts above the normalized query table with count, instance and wait events columns](/images/apm/database-monitoring/pg-query-metrics.png)

## Charts

Two charts at the top show trends for the queries in the table. Choose the metric for each chart from its dropdown:

- **Query count**
- **Total Duration**
- **Avg Duration**
- **P95 Duration**

Each line is one query. Hover over a chart to see the value for each query. Your chart choices are remembered.

> **Note:** For PostgreSQL, counts and durations are calculated from query samples, so **Count** is the number of sampled executions. See [How It Works](/features/apm/database-monitoring#how-it-works).

## Query Table

#### PostgreSQL

| Column | Description |
| --- | --- |
| **Normalized query** | Query text with literal values replaced by `?` |
| **Count** | Number of sampled executions in the time range |
| **Avg Duration** | Average execution time, with a bar scaled to the slowest query |
| **Total Duration** | Sum of execution time across samples |
| **Instance** | The PostgreSQL instance the query ran on |
| **Wait Events** | A stacked bar showing which wait event groups the query's samples were in. Hover over it to see the count and percentage per wait event type. |

#### MongoDB

Default columns:

| Column | Description |
| --- | --- |
| **Query statement** | The operation as JSON, for example `{"$db":"shop","find":"orders",...}` |
| **Query signature** | Hash that identifies the shape of the operation |
| **Operation** | `insert`, `query`, `update`, `remove`, `command`, `getmore`, and so on |
| **Namespace** | `database.collection` |
| **Count** | Number of profiled executions |
| **Avg Duration** / **Total Duration** | Operation time from the profiler |
| **Avg Docs examined** | Average documents scanned per execution |
| **Host** | The MongoDB host |

Optional columns: **Avg Keys examined**, **Avg Returned**, **Avg Modified**, **Avg Inserted**, **Avg Deleted**, **Avg Keys Inserted**, **Avg Write Conflicts**, **Avg Yields**, **Avg CPU Time**, **Avg Planning Time**, and **Avg Response Length**.

Table controls:

- **Full Query Text**: shows complete query text instead of truncating it.
- **Customize**: choose which columns to show, then click **Apply Changes**.
- Sort by clicking a column header. Use the search bar at the top of the page to filter by query text.

![MongoDB Query Metrics table with query statement, signature, operation, namespace, count and documents examined](/images/apm/database-monitoring/mongo-query-metrics.png)

## Query Details

Click a query to open its detail panel.

- **View Query Samples** opens the [Samples](/features/apm/database-monitoring/samples) tab filtered to this query.
- **Filter to Query** adds the instance and query to the page search, so every tab shows only this query.

The top of the panel shows the instance, the **Query** text, **Tags** collected from recent executions, and **Avg Duration**, **Total Duration**, and **Count** charts.

### PostgreSQL

![PostgreSQL query details with query text, tags, duration and count charts, and the Upstream tab listing calling services](/images/apm/database-monitoring/pg-query-details.png)

Click the arrow next to **Query** to format the SQL. **Tags** include `db.instance`, `db.namespace` (database), `service.instance.id`, backend type, `user.name`, and the client address.

| Tab | What it shows |
| --- | --- |
| **Upstream** | **Calling Services**: the APM services that sent this query. **Traces**: the APM spans linked to the query's samples, with **Open in Traces**. Needs [APM trace correlation](/features/apm/database-monitoring/connect-apm-traces). |
| **Metrics** | Count and durations, plus average rows, shared block hits, reads, dirtied and written blocks, temp block reads and writes, and block read and write time. Block, row, and I/O time charts need **Top Query Collection**, and I/O time needs `track_io_timing`. |
| **Samples** | The samples for this query, with the activity chart |
| **Users** | Samples, average duration, and total duration per database user |
| **Applications** | Samples, average duration, and total duration per `application_name` |
| **Explain Plans** | The latest execution plan for this query. See [Explain Plans](#explain-plans). |
| **Blocking Activity** | **Blocking Overview** and **Blocking Samples** for this query |

### MongoDB

![MongoDB query details with the statement JSON, tags, duration and count charts and per-execution metrics](/images/apm/database-monitoring/mongo-query-details.png)

The **Query** section has five views of the latest execution: **Statement**, **RawQuery**, **Cursor**, **Locks**, and **FlowControl**. **Tags** include the host, namespace, operation, plan summary, and query ID.

| Tab | What it shows |
| --- | --- |
| **Metrics** | Operation time, response length, CPU time, and documents and keys examined, inserted, returned, matched, modified, and deleted, plus write conflicts |
| **Samples** | Individual executions of this operation |

## Explain Plans (PostgreSQL)

The **Explain Plans** tab shows the most recent plan the agent captured for the query within the selected time range. Plans come from **Top Query Collection** and are produced with `EXPLAIN`, so the query is never executed to get them.

![Explain Plans tab showing a Seq Scan query plan with planner cost, estimated rows and a sequential scan warning](/images/apm/database-monitoring/pg-explain-plan.png)

Two views are available:

- **Explained**: a readable plan tree.
- **Json**: the raw `EXPLAIN (FORMAT JSON)` output.

The **Explained** view contains:

- **Plan summary**: the root operation (for example `Seq Scan`, `Hash Join`, `Index Scan`), **Planner cost**, **Est. rows** (or **Actual rows** when present), and **Planning** and **Execution** time when available.
- **Sequential scan detected**: a warning shown when any step reads a full table. Consider adding an index or a more selective filter if the query is slow.
- **Tables**, **Indexes**, and **Access**: the tables and indexes the plan touches, and the scan and join methods it uses.
- **Plan steps**: every plan node, nested under its parent. Each node shows its type, **Planner cost** (startup → total), estimated rows, loops, workers, the table or index it reads, and details such as `Filter`, `Index Cond`, `Hash Cond`, and `Sort Key`.

If no plan is available, the tab shows "No explain plan found for this query in the selected time range." See [PostgreSQL troubleshooting](/get-started/database/postgresql#troubleshooting).

## Wait Events and Blocking (PostgreSQL)

Every PostgreSQL query sample records the wait event the session was in when sampled. Wait events show *why* a query is slow: waiting on locks, disk, the client, or internal resources.

| Wait event group | What the session was doing |
| --- | --- |
| No wait event | Running, not waiting. Shown in green, labelled **Activity** in charts and **—** in tables. |
| **Lock** | Waiting for a heavyweight lock held by another session (row or table locks) |
| **LWLock** | Waiting for a lightweight internal lock, such as a buffer mapping or WAL lock |
| **IO** | Waiting for a disk read or write |
| **Client** | Waiting for the client application to send or read data |
| **IPC** | Waiting for another server process |
| **BufferPin** | Waiting to access a data buffer another process is using |
| **Activity** | A background process waiting for work. Uses the same green as running queries. |
| **Timeout** | Waiting for a timeout to expire |
| **Extension** | Waiting inside an extension |

Wait event groups appear in the **Wait Events** column of the query table, in the **Load By Wait Group** column of the instance list, in the instance **Average Load** chart, and in the [Samples](/features/apm/database-monitoring/samples) tab.

**Blocking**: when a session waits on a `Lock`, PostgreSQL reports which sessions block it. Database Monitoring uses this to separate **root blocking queries** (the queries holding the lock) from **waiting queries**. The **Blocking Overview** table lists:

| Column | Description |
| --- | --- |
| **Root blocking query** | The query at the head of the lock chain |
| **Tables** | Tables involved |
| **Max block time** | Longest time another query waited on it |
| **Total block time** | Sum of wait time it caused |
| **Occurrences** | Number of blocking events |

**Blocking Samples** lists the individual samples, including **Blocking Pids**. You can find blocking data in the instance **Summary → Blocking Queries** section, the instance **Queries** tab, and each query's **Blocking Activity** tab.

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