Compare Schemas
Compare Schema enables users to track and analyze changes in database schema structures. This tool compares tables and columns to identify structural modifications, pinpoint specific column-level changes, and monitor schema evolution over time.
The Compare Schema is particularly useful in environments that require version control, change tracking, and lineage validation to support governance and audit readiness.
Key Capabilities:
Compare the same schema across different crawl dates.
Compare two different schemas across connectors.
Retain comparison results and schema pairing history.
Schedule recurring comparisons and receive notifications.
Perform impact analysis based on schema changes.
Access Control:
Users with the Author role and Metadata Write access can utilize the Compare Schema, which is available under the Advanced Tools.
Example:
An Employee table in a MySQL database has a column named Employee address.
This column initially had a CHAR data type with a 20-character limit (crawled on 2025-01-25 at 17:02:34).
Later, the limit was increased to 30 characters to accommodate longer addresses (recrawled on 2025-02-28 at 14:04:25).
Result:
A schema comparison would identify the Employee address column as modified.
Steps for Comparing Schemas
Access the Compare Schema Tool
Navigate to Advanced Tools and select Compare Schema.
The Compare Schema home page displays the comparison history, including the Title, Source Connector, Source Schema, Target Connector, Target Schema, Created By, and Created On.
Create a New Schema Comparison
Click the + Compare Schema button.
In the pop-up window, enter the Title for the comparison folder.
Select the Source and Target connectors and schemas to be compared.
Define Source Schema
Select the source connector (e.g., MySQL).
Specify the source schema (e.g., information_schema).
Select the crawl date representing the source schema state (e.g., 2025-02-16).
Define Target Schema
Select the target connector (e.g., MySQL).
Specify the target schema (e.g., information_schema).
Select the crawl date representing the target schema state (e.g., 2025-02-26).
Click Save. The new comparison folder appears in the Compare Schema History with the selected source and target pair.
Run a Schema Comparison
Select the comparison Title from the history.
Click the 9-dot menu, then select Compare.
The tool checks for any existing comparison:
If results exist, they are displayed immediately.
If not, the comparison job is submitted.
Job Statuses
INIT – The job has been initiated.
WAITING – The job is queued and awaiting execution.
RUNNING – The job is currently executing.
SUCCESS – The comparison was completed successfully.
PARTIAL SUCCESS – The comparison was partially completed.
ERROR – The job failed; error details can be viewed in the logs.
KILLED – The job was terminated manually.
Click Refresh to update the job status and monitor progress.
Once the job is successful, a confirmation message appears. Click the Title to open the Compare Schema Results page.
Re-run Schema Comparison
Users can click on "Re-run" to view the latest results of schema comparisons.
Re-run with Existing Settings: Clicking "Re-run" without changing any input fields will fetch the most recent data for the previously selected schemas, providing an updated comparison.
Review Results
Column Change Summary
Lists affected tables.
Shows the number of modified columns.
Indicates how many times each column changed.
Column Change Details
Displays the Comparison ID.
Lists the table and column names with changes.
Shows data types and lengths in both source and target.
Identifies change types (added, deleted, or modified).
Includes action timestamps.
Offers filters to sort by change type.
These results highlight schema differences between the selected crawl dates (e.g., 2025-02-16 to 2025-02-26).
Additional Features
Download Results – Export the comparison report as a CSV file.
Impact Analysis – Analyze downstream effects of column changes.
Watchlist Notifications – Receive alerts when schema changes are detected.
Schedule Compare Schema
Users can schedule schema comparisons for regular execution.
Steps to Schedule
From the Compare Schema History, select the Title.
Click the 9-dot menu and select Schedule. The Schedule pop-up window is displayed.
In the schedule window, configure the following settings:
Set Frequency: From the "Every" dropdown, select "Year".
Select Month: In the In field, choose JAN.
Choose Day: In the On field, select 1.
Set Time: In the At field, select 12 (for 12 PM).
In the Minutes field, enter 0.
This configuration schedules the comparison for January 1st at 12:00 PM annually.
Click Schedule to activate.
Click Cancel to discard changes.
Delete Schema Comparison
From the Compare Schema History, select the desired Title.
Click the 9-dot menu and select Delete.
A confirmation message — "Are you sure you want to delete the schema comparison?" — is displayed.
Click the Delete button to permanently remove the selected schema comparison from the Compare Schema History.
Comparison of Same Schema
Users can analyze how a schema within the same connector has changed over time:
Click the + Compare Schema button.
In the pop-up window, enter the Title for the comparison folder.
Connector: Select the connector where the schema resides for Connector [A] and Connector [B].
Schema: Choose the specific schema they want to compare against itself at different points in time for Schema [A] and Schema [B].
Date for Schema A: Select the starting date for the initial state of the schema. Here, the dropdown will show all the crawled dates for the selected schema.
Date for Schema B: Select the ending date representing the later state of the schema. Here, the dropdown will show all the crawled dates for the selected schema.
Click Save. The new comparison folder appears in the Compare Schema History with the selected source and target pair.
Select the comparison Title from the history.
Click the 9-dot menu, then select Compare.
The tool checks for any existing comparison:
If results exist, they are displayed immediately.
If not, the comparison job is submitted.
Once the job is successful, a confirmation message appears. Click the Title to open the Compare Schema Results page.
By providing these details, users can identify changes made to the schema between the specified dates. This helps track schema evolution, maintain data consistency over time, and ensure their schema remains consistent across timeframes.
Comparison of Different Schemas
Users can analyze how a schema from different connectors has changed over time:
Click the + Compare Schema button.
In the pop-up window, enter the Title for the comparison folder.
Connector [A]: Choose the connector where their first schema resides (the reference point).
Schema [A]: Select the specific schema to compare within Connector [A].
Connector [B]: Identify the connector where their second schema is located.
Schema [B]: Choose the schema from Connector [B] for comparison.
Click Save. The new comparison folder appears in the Compare Schema History with the selected source and target pair.
Select the comparison Title from the history.
Click the 9-dot menu, then select Compare.
The tool checks for any existing comparison:
If results exist, they are displayed immediately.
If not, the comparison job is submitted.
Once the job is successful, a confirmation message appears. Click the Title to open the Compare Schema Results page.
By providing these details, users gain valuable insights into data changes, historical trends, and potential discrepancies between schemas, and allow users to:
Ensure data quality and consistency across systems.
Make informed data-related decisions with confidence.
Expand Impact Analysis
OvalEdge allows users to incorporate tables and columns from schema comparison results (using the "9 Dots" menu options) into their impact analysis.
Include Deleted Tables: Users can add tables identified as deleted in their schema comparison to an impact analysis. This helps users understand the impact of their removal and make informed data-driven decisions.
Include Deleted Columns: Users can analyze the effects of deleted columns by including them in their impact analysis. These removed columns can have a significant impact on downstream processes. Adding them helps users assess the consequences of their absence.
Include Changed Columns: Users can utilize schema comparison results to add changed columns to their impact analysis. This helps users understand how these alterations might influence data operations, allowing them to stay proactive in managing potential issues.
Add to Impact Analysis: Users can add specific objects identified in the schema comparison to their impact analysis. This enables users to tailor the analysis to their particular concerns or areas of interest.
Download Schema Comparison Results
OvalEdge enables users to download their schema comparison results for further analysis and record-keeping purposes.
The download button is located at the bottom right corner of the results page. The downloadable file, often in CSV format, provides a valuable resource for detailed analysis, allowing users to explore the comparison data in their preferred analysis tools and conduct a deeper dive into specific changes.
Decode Schema Comparison Results
OvalEdge's Schema Comparison tool provides insightful reports to help users understand changes between database schemas. Here's a breakdown of the key sections:
Column Change Summary
List of Tables: This section provides an overview of all tables affected by the comparison.
Column Change Count: This value represents the total number of columns modified within the specified timeframe.
Total Change Count: This metric indicates the cumulative number of times individual columns have been modified across the comparison period.
Example: The "information_schema" schema has changed from 2024-02-16 to 2024-02-26. The summary reveals the number of affected tables, the total number of columns modified, and the overall number of modifications within those columns.
Column Change Details
This section offers a detailed breakdown of individual column changes:
Compare ID: A unique identifier for the comparison run.
Table Name: The specific table where the column change occurred.
Column Name: The name of the modified column.
Column Type & Length (Source/Target): Displays the data type and length of the column in both the source and target schemas, highlighting any alterations.
Action Date & Taken: Indicates the modification date and the specific action performed (Added, Deleted, or Modified).
Filtering Options: Users can filter the detailed report to view changes based on the type of action taken (Added, Deleted, Modified), enabling a focused analysis.
Example: The detailed report for the "information_schema" schema (compared between 2024-02-16 to 2024-02-26) showcases individual column modifications, including the specific columns affected, changes in data type or length, and the date and nature of the action taken (added, deleted, or modified). Additionally, users can filter this data to view only specific types of changes for a more granular analysis.
Copyright © 2025, OvalEdge LLC, Peachtree Corners, GA, USA.
Last updated
Was this helpful?