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https://issues.apache.org/jira/browse/PHOENIX-8000?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Viraj Jasani updated PHOENIX-8000:
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Summary: Conditional TTL is not enforced at compaction for SYSTEM tables
(was: Conditional TTL is not enforced at compaction for SYSTEM tables — expired
rows are never physically purged (e.g. SYSTEM.CDC_STREAM))
> Conditional TTL is not enforced at compaction for SYSTEM tables
> ---------------------------------------------------------------
>
> Key: PHOENIX-8000
> URL: https://issues.apache.org/jira/browse/PHOENIX-8000
> Project: Phoenix
> Issue Type: Bug
> Components: phoenix
> Affects Versions: 5.3.0, 5.3.1, 5.3.2
> Reporter: Shubham Roy
> Assignee: Shubham Roy
> Priority: Minor
> Fix For: 5.4.0, 5.3.3
>
>
> h2. Summary
> A SYSTEM table configured with a *conditional TTL* never has that TTL applied
> during compaction. Expired rows are hidden at read time (masking) but are
> *never physically removed* from the HFiles, so they accumulate indefinitely.
> \{{SYSTEM.CDC_STREAM}} — created with a conditional TTL to expire
> closed-partition rows after a minimum age — is the concrete instance.
> h2. Root cause
> In \{{CompactionScanner.NonPartitionedTableTTLTracker}}, SYSTEM tables are
> unconditionally routed to the HBase column-family *descriptor* TTL instead of
> the table's compiled *conditional* TTL expression:
> {code:java}
> boolean isSystemTable = pTable.getType() == PTableType.SYSTEM;
> ...
> if (isSystemTable
> ||
> pTable.getTTLExpression().equals(TTL_EXPRESSION_DEFINED_IN_TABLE_DESCRIPTOR))
> {
> ColumnFamilyDescriptor cfd = store.getColumnFamilyDescriptor();
> ttlExpr = TTLExpressionFactory.create(cfd.getTimeToLive()); // descriptor
> TTL, NOT the conditional expr
> } else {
> ttlExpr = !pTable.getTTLExpression().equals(TTL_EXPRESSION_NOT_DEFINED)
> ? pTable.getCompiledTTLExpression(pConn) // conditional path - skipped for
> SYSTEM
> : TTL_EXPRESSION_FOREVER;
> }
> {code}
> For a table whose TTL is a *conditional* expression, the CF-descriptor TTL is
> \{{FOREVER}} (Phoenix stores a numeric TTL in the descriptor only for
> _literal_ expressions; conditional TTLs are stored in SYSTEM.CATALOG and the
> descriptor is left \{{FOREVER}}). Consequently, for a SYSTEM table:
> * \{{ttlExprForRow}} resolves to a literal \{{FOREVER}}, so
> \{{RowContext.hasConditionalTTL()}} is always \{{false}};
> * therefore \{{postProcessForConditionalTTL(...)}} — the only place the
> conditional expression is evaluated and an expired row is dropped
> (\{{result.clear()}}) — is *never reached*;
> * so expiry is enforced *only* as read-time masking (\{{TTLRegionScanner}}),
> never at compaction.
> Minor compaction / flush also never purge (they use
> \{{TTL_EXPRESSION_FOREVER}} by design), so major compaction is the only place
> this _should_ happen — and it does not for SYSTEM tables.
> h2. Steps to reproduce
> # Create/use a SYSTEM table with a conditional TTL (e.g.
> \{{SYSTEM.CDC_STREAM}}, whose TTL is {{PARTITION_END_TIME IS NOT NULL AND
> TO_NUMBER(CURRENT_TIME()) - TO_NUMBER(PHOENIX_ROW_TIMESTAMP()) >=
> <min-age>}}, default ~30h).
> # Insert rows that satisfy the expiry condition and advance the clock past
> the min age.
> # Trigger a major compaction on the table.
> *Observed:* the rows are still physically present in the HFiles (a raw /
> all-versions scan still returns them); they are only hidden from normal
> Phoenix reads.
> *Expected:* the expired rows are physically removed by the major compaction.
> h2. Expected behavior
> SYSTEM tables should honor their conditional TTL at (major) compaction —
> evaluating the compiled conditional expression and physically purging
> matching rows — the same way non-SYSTEM tables do. The \{{isSystemTable}}
> short-circuit should not force a conditional-TTL table onto the
> (\{{FOREVER}}) descriptor TTL.
> h2. Proposed fix
> In \{{NonPartitionedTableTTLTracker}}, do not route a SYSTEM table to the
> descriptor TTL when it has a *conditional* TTL expression; use the table's
> compiled conditional TTL (\{{pTable.getCompiledTTLExpression(...)}}) so
> \{{hasConditionalTTL()}} becomes true and
> \{{postProcessForConditionalTTL(...)}} runs at major compaction. Keep the
> descriptor-TTL path only for tables that define TTL in the descriptor /
> literal TTLs.
> h2. Test
> Add an integration test that:
> * uses a SYSTEM table with a conditional TTL (\{{SYSTEM.CDC_STREAM}}),
> * writes rows satisfying the condition and ages them past the configured
> min-age (~30h),
> * runs a *major compaction*, and
> * asserts the expired rows are *physically removed* (e.g. a raw /
> all-versions scan no longer returns them), not merely masked.
> h2. Impact
> Any SYSTEM table with a conditional TTL retains expired rows on disk forever,
> causing unbounded growth of the system table and defeating the intent of the
> conditional TTL (rows are hidden but never reclaimed).
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