Adding New Queryable Columns

This guide explains how to add a new column to ntopng so that it can be queried from the frontend Historical Flows page.

Overview

To expose a new column in the historical flow search:

Update the database schema to include the new column.
Synchronize all ClickHouse/C++ schema definitions.
Update tag utils to support filtering.
Modify flow column definitions to link tags and database fields.
Ensure the REST API returns and formats the new column.

Steps

1. Modify the ClickHouse Schema

Edit the schema file:

httpdocs/misc/db_schema_clickhouse.sql

Add the new column to the appropriate flow table (e.g., flows, aggregated_flows_hourly, etc.).
At the top of the SQL file, you'll find a list of 4 scripts that must be kept in sync when updating the schema. Update those C++ and Lua files accordingly to ensure consistency.

2. Update Tag Utilities

Edit the tag definition in:

scripts/lua/modules/tag_utils.lua

Add an entry for your new column (example: dst_peer_as):

dst_peer_as = {
    value_type = 'asn',
    i18n_label = i18n('db_search.tags.dst_peer_as'),
    operators = { 'eq', 'neq' },
    hourly_available = false,
},

The hourly_available field should be set to true if you want the field usable in hourly aggregations.
i18n label is the entry in the i18n file (scripts/locales/en.lua) that renders the label for the newly created tag.

3. Update Historical Flow Utils

Edit:

scripts/lua/modules/historical_flow_utils.lua

Add the new column to the flow_columns table:

['DST_PEER_ASN'] = { tag = "dst_peer_asn" },

The key (DST_PEER_ASN) should match the column name in ClickHouse (uppercase).
The tag must correspond to the tag defined in tag_utils.lua.

4. Handle Aggregates (Optional)

If aggregations (e.g., hourly) are enabled, ensure the new column is also available in:

Aggregated flow tables in db_schema_clickhouse.sql
Add the new columns definition to scripts/lua/modules/historical_flow_utils.lua aggregated_flow_columns.

5. Update REST API Formatting

Edit:

pro/scripts/lua/rest/v2/get/flow/historical/flow_details.lua

Find and update the historical_flow_details_formatter.formatHistoricalFlowDetails(flow) function to include your new column:

formatted_flow.dst_peer_asn = flow.dst_peer_asn

This ensures the new field is visible in the frontend when rendering historical flow details.

Summary

To add a new column for querying and displaying in the historical flow UI, update the following files:

Schema: httpdocs/misc/db_schema_clickhouse.sql
C++/Lua schema sync: Top 4 files listed in the schema file
Tags: scripts/lua/modules/tag_utils.lua
Flow Utils: scripts/lua/modules/historical_flow_utils.lua
REST API: pro/scripts/lua/rest/v2/get/flow/historical/flow_details.lua

Ensure that all parts are in sync to allow querying, filtering, and rendering of the new column.

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