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https://issues.apache.org/jira/browse/CASSANDRA-19662?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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BHARATH KUMAR updated CASSANDRA-19662:
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Attachment: BufferUnderflow_plus_error
> Data Corruption and OOM Issues During Schema Alterations
> ---------------------------------------------------------
>
> Key: CASSANDRA-19662
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19662
> Project: Cassandra
> Issue Type: Bug
> Components: Client/java-driver
> Reporter: BHARATH KUMAR
> Priority: Normal
> Attachments: BufferUnderflow_plus_error
>
>
> h2. Description
>
> *Overview:* The primary issue is data corruption occurring during schema
> alterations (ADD/DROP column) on large tables(300+ columns and 6TB size ) in
> the production cluster. This is accompanied by out-of-memory (OOM) errors and
> other exceptions, specifically during batch reads. This problem has been
> replicated on multiple clusters, running Apache Cassandra version 4.0.12 and
> Datastax Java Driver Version: 4.17
> *Details:*
> *Main Issue:*
> * *Data Corruption:* When dynamically adding a column to a table, the data
> intended for the new column is shifted, causing misalignment in the data.
> * *Symptoms:* The object implementing
> {{com.datastax.oss.driver.api.core.cql.Row}} returns values shifted against
> the column names returned by {{{}row.getColumnDefinitions(){}}}. The driver
> returns a corrupted row, leading to incorrect data insertion.
> *Additional Issues:*
> *Exceptions:*
> * {{java.nio.BufferUnderflowException}} during batch reads when ALTER TABLE
> ADD/DROP column statements are issued.
> * {{java.lang.ArrayIndexOutOfBoundsException}} in some cases.
> * Buffer underflow exceptions with messages like "Invalid 32-bits integer
> value, expecting 4 bytes but got 292".
> * OOM errors mostly occur during ADD column operations, while other
> exceptions occur during DELETE column operations.
> * *Method Specific:* Errors occur specifically with
> {{{}row.getList(columnName, Float.class){}}}, returning incorrect values.
> *Reproducibility:*
> * The issue is reproducible on larger tables (300 columns, 6 TB size) but
> not on smaller tables.
> * SELECT * statements are used during reads
> * *Method Specific:* Errors occur specifically with
> {{{}row.getList(columnName, Float.class){}}}, returning incorrect values.
> However, the code registers a driver exception when calling the method
> {{{}row.getList(columnName, Float.class){}}}. We pass the exact column name
> obtained from {{{}row.getColumnDefinition{}}}, but it returns the wrong value
> for a column with this name. This suggests that the issue lies with the
> driver returning an object with incorrect properties, rather than with the
> SQL query itself.
> *Debugging Efforts:*
> * *Metadata Refresh:* Enabling metadata refresh did not resolve the issue.
> * *Schema Agreement:* {{session.getCqlSession().checkSchemaAgreement()}} did
> not detect inconsistencies during test execution.
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