In the Query summary section of the query execution, check for the
Columnar read share information.
The following image shows the Columnar read share percentage:
This metric shows the percentage of bytes read from columnar storage out of
total bytes read from both row-based and columnar storage. A high percentage is
optimal, while a low percentage suggests that much of the data remains
unconverted to columnar format.
Columnar data storage metrics
To view columnar data storage metrics:
Go to the Spanner Instances page in the Google Cloud console.
In the Storage usage section, you can see two new metrics:
columnar storage - hdd and columnar storage - ssd. These metrics
show the columnar representation usage of HDD and SSD. The total storage
metrics include both PAX and columnar data. You can see these metrics on
storage usage graphs on the System insights page. For example:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[],[],null,["# Monitor columnar engine performance\n\n| **Preview\n| --- [Spanner columnar engine](/spanner/docs/columnar-engine)**\n|\n|\n| This feature is subject to the \"Pre-GA Offerings Terms\" in the General Service Terms section\n| of the [Service Specific Terms](/terms/service-terms#1).\n|\n| Pre-GA features are available \"as is\" and might have limited support.\n|\n| For more information, see the\n| [launch stage descriptions](/products#product-launch-stages).\n|\n|\n| For information about access to this\n| release, see the\n| [access request page](https://forms.gle/nE1bAqfHJrqhkStR9).\n\n\n| **PostgreSQL interface note:** The examples in this topic are intended for GoogleSQL-dialect databases. This feature doesn't support PostgreSQL interface.\n\n\u003cbr /\u003e\n\nThis page describes how to monitor Spanner's columnar engine. You\ncan monitor using:\n\n- [The query execution plan](#columnar-data-query-plan)\n- [Storage usage](#monitor-storage-usage) graphs in [system insights](#monitor-storage-usage)\n\nView columnar data in the query plan\n------------------------------------\n\n1. Run a query.\n2. View its [query plan](/spanner/docs/query-execution-plans).\n3. In the **Query summary** section of the query execution, check for the\n **Columnar read share** information.\n\n The following image shows the **Columnar read share** percentage:\n\nThis metric shows the percentage of bytes read from columnar storage out of\ntotal bytes read from both row-based and columnar storage. A high percentage is\noptimal, while a low percentage suggests that much of the data remains\nunconverted to columnar format.\n\nColumnar data storage metrics\n-----------------------------\n\nTo view columnar data storage metrics:\n\n1. Go to the **Spanner Instances** page in the Google Cloud console.\n\n [Go to the Instances page](https://console.cloud.google.com/spanner/instances)\n2. Select the instance you want to view metrics for.\n\n3. Click **System insights**.\n\n4. In the **Storage usage** section, you can see two new metrics:\n\n **columnar storage - hdd** and **columnar storage - ssd** . These metrics\n show the columnar representation usage of HDD and SSD. The total storage\n metrics include both PAX and columnar data. You can see these metrics on\n storage usage graphs on the **System insights** page. For example:\n\nWhat's next\n-----------\n\n- Learn about [columnar engine](/spanner/docs/columnar-engine).\n- Learn how to [enable columnar engine](/spanner/docs/configure-columnar-engine).\n- Learn how to [query columnar data](/spanner/docs/query-columnar-data)."]]
