BIDialectProvider

Property	Value
Interface Type	provider
Module	extra-core
Full Class Name	`com.finebi.api.dialect.BIDialectProvider`
Official Docs	N/A

Overview

An extension point for integrating custom database dialects into FineBI. By providing a mapping function from the platform Dialect to a custom BIDialect, FineBI can generate correct SQL for a specific database.

Note: The FineBI service must be restarted after the plugin is enabled for changes to take effect.

For background on related requirements, see: KERNEL-15316 "BI Support for Custom Dialects".

Interface Definition

@Open
public interface BIDialectProvider extends Mutable {

    String XML_TAG = "BIDialectProvider";

    int CURRENT_LEVEL = 1;

    /**
     * Returns a function that maps a platform Dialect to a custom BIDialect.
     * Return Optional.empty() if the current Dialect does not require custom handling.
     */
    Function<Dialect, Optional<BIDialect>> getBIDialect();
}

Core BIDialect Interface

BIDialect is the core of dialect adaptation. It is recommended to extend AbstractBIDialect and override the following methods as needed:

Method	Description
`getDSLContext()`	Core method: Returns a jooq DSLContext used for SQL generation
`getFieldInfoSql()`	Returns the SQL for retrieving result set field info; return `empty` to use the default implementation
`getDialectResultSet()`	Wraps a ResultSet to apply dialect adaptations during data retrieval
`isSupportCTE()`	Whether CTE is supported
`windowFunctionNotSupportXxx()`	Window function support for each aggregate (SUM/AVG/MAX/MIN/Variance, etc.)
`isTopNConditionByExists()`	Whether TopN is implemented via an EXISTS subquery
`isTopNUseWindowFunction()`	Whether TopN is implemented via a window function
`isRowNumberWithoutOrderBy()`	Whether `row_number` can omit ORDER BY
`castIntegerWithOverFlow()`	Explicit type cast for integer overflow in SUM and similar functions
`castIntegerWithPrecision()`	Type cast for AVG integer precision issues
`checkGroups()`	Custom GROUP BY handling logic
`isSortNullFirst()` / `isSortNullLast()`	Position of NULL values during sorting
`isUseAliasInOrder()`	Whether to use aliases in ORDER BY (e.g., Hive)
`alwaysUseCrossJoin()`	Always use CROSS JOIN syntax
`needNullCast()`	Whether NULL values require an explicit CAST
`isEqualsWithNullAndEmptyString()`	Whether NULL and empty string are treated as equivalent
`onlySupportCountAll()`	Whether only `COUNT(*)` is supported
`previewRemoveLastColumn()`	Whether to remove the last column in SQL preview (e.g., Oracle's `rn`)

Usage

<extra-core>
    <BIDialectProvider class="com.fr.plugin.xxx.YourBIDialectProvider"/>
</extra-core>

Example Code

The following is a reference implementation for YashanDB dialect adaptation:

// 1. Implement BIDialectProvider to map the Yashan Dialect to a custom BIDialect
public class YashanBIDialectProvider implements BIDialectProvider {

    @Override
    public Function<Dialect, Optional<BIDialect>> getBIDialect() {
        return dialect -> {
            // Check whether this is a YashanDB Dialect
            if (dialect instanceof YashanDialect) {
                return Optional.of(new YashanBIDialect(dialect));
            }
            return Optional.empty();
        };
    }
}

// 2. Extend AbstractBIDialect and override dialect behaviors as needed
public class YashanBIDialect extends AbstractBIDialect {

    public YashanBIDialect(Dialect dialect) {
        super(dialect);
    }

    @Override
    public boolean windowFunctionNotSupportVariance() {
        return true;  // YashanDB does not support Variance window functions
    }

    @Override
    public boolean windowFunctionNotSupportStandardDeviation() {
        return true;  // YashanDB does not support StandardDeviation window functions
    }

    @Override
    public boolean isEqualsWithNullAndEmptyString() {
        return true;  // YashanDB treats NULL and "" as equivalent
    }

    @Override
    public boolean previewRemoveLastColumn() {
        return false;
    }

    @Override
    public DSLContext getDSLContext() {
        // Based on Oracle dialect with custom SQL generation logic
        return DSL.using(new CustomConfiguration(SQLDialect.ORACLE,
            new DefaultSqlCreator(SQLDialect.ORACLE) { /* custom function implementations */ }
        ));
    }
}

Notes

getDSLContext() is the core of jooq SQL generation. Implementation requires familiarity with jooq; refer to the platform's existing database dialect implementations for guidance.
In the function returned by getBIDialect(), return Optional.of(...) only for the target Dialect type and Optional.empty() for all others to avoid affecting other databases.
The FineBI service must be restarted after installing or upgrading the plugin for it to take effect.
Extending AbstractBIDialect provides default implementations for most methods; only override methods where the database behavior differs.

FineBI Entry Points