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Java query hints #1942

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Update Java Query Hints
MattSchur Jun 30, 2025
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MattSchur Jun 30, 2025
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2 changes: 1 addition & 1 deletion java/cqn-services/persistence-services.md
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Expand Up @@ -147,7 +147,7 @@ By default, the SAP HANA adapter in CAP Java generates SQL that is optimized for
cds.sql.hana.optimizationMode: legacy
```

Use the [hints](../working-with-cql/query-execution#hana-hints) `hdb.USE_HEX_PLAN` and `hdb.NO_USE_HEX_PLAN` to overrule the configured optimization mode per statement.
Use the [hints](../working-with-cql/query-execution#query-hints) `hdb.USE_HEX_PLAN` and `hdb.NO_USE_HEX_PLAN` to overrule the configured optimization mode per statement.

::: warning Rare error in `HEX` mode
In some corner cases, particularly when using [native HANA views](../../advanced/hana#create-native-sap-hana-objects), queries in `HEX` optimization mode may fail with a "hex enforced but cannot be selected" error. This is the case if the statement execution requires the combination of HEX only features with other features that are not yet supported by the HEX engine. If CAP detects this error it will, as a fallback, execute the query in _legacy_ mode.
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10 changes: 5 additions & 5 deletions java/working-with-cql/query-execution.md
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Expand Up @@ -117,15 +117,15 @@ var params = Map.of("minStock", 100);
Result result = service.run(query, params);
```

#### Adding Query Hints for SAP HANA { #hana-hints}
### Query Hints { #query-hints}

To add a hint clause to a statement, use the `hints` method and prefix the [SAP HANA hints](https://help.sap.com/docs/HANA_CLOUD_DATABASE/c1d3f60099654ecfb3fe36ac93c121bb/4ba9edce1f2347a0b9fcda99879c17a1.htmlS) with `hdb.`:
Use the `hints` method to add specific hints to a CDS QL statement. [SAP HANA hints](https://help.sap.com/docs/HANA_CLOUD_DATABASE/c1d3f60099654ecfb3fe36ac93c121bb/4ba9edce1f2347a0b9fcda99879c17a1.htmlS) need to be prefix with `hdb.`
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Use the `hints` method to add specific hints to a CDS QL statement. [SAP HANA hints](https://help.sap.com/docs/HANA_CLOUD_DATABASE/c1d3f60099654ecfb3fe36ac93c121bb/4ba9edce1f2347a0b9fcda99879c17a1.htmlS) need to be prefix with `hdb.`
Use the `hints` method to add database-specific hints to a CDS QL statement. [SAP HANA hints](https://help.sap.com/docs/HANA_CLOUD_DATABASE/c1d3f60099654ecfb3fe36ac93c121bb/4ba9edce1f2347a0b9fcda99879c17a1.htmlS) need to be prefix with `hdb.`

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Use the `hints` method to add specific hints to a CDS QL statement. [SAP HANA hints](https://help.sap.com/docs/HANA_CLOUD_DATABASE/c1d3f60099654ecfb3fe36ac93c121bb/4ba9edce1f2347a0b9fcda99879c17a1.htmlS) need to be prefix with `hdb.`
Use the `hints` method to add specific hints to a CDS QL statement that override the default behavior of the CAP Java runtime or influence the query execution on the database. Supported runtime hints are documented together with the runtime behavior.
[SAP HANA hints](https://help.sap.com/docs/HANA_CLOUD_DATABASE/c1d3f60099654ecfb3fe36ac93c121bb/4ba9edce1f2347a0b9fcda99879c17a1.htmlS) need to be prefix with `hdb.`


```java
CqnSelect query = Select.from(BOOKS).hints("hdb.USE_HEX_PLAN", "hdb.ESTIMATION_SAMPLES(0)");
Select.from(BOOKS).hints("hdb.USE_HEX_PLAN", "hdb.HEX_INDEX_JOIN");
```
::: warning
Hints prefixed with `hdb.` are directly rendered into SQL for SAP HANA and therefore **must not** contain external input!
::: danger
Hints prefixed with `hdb.` are directly rendered into SQL for SAP HANA and **must not** contain untrusted input!
:::

### Data Manipulation
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