org.apache.cayenne.query

## Interface QueryMetadata

-     public interface QueryMetadata

  Provides a common interface for accessing query metadata.
  Since:
    1.2

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `CACHE_GROUPS_PROPERTY`
    `static String` | `CACHE_STRATEGY_PROPERTY`
    `static int` | `FETCH_LIMIT_DEFAULT` Defines default query fetch limit, which is zero, meaning that all matching rows should be fetched.
    `static String` | `FETCH_LIMIT_PROPERTY` Defines the name of the property for the query `fetch limit` .
    `static int` | `FETCH_OFFSET_DEFAULT` Defines default query fetch start index, which is 0, meaning that matching rows selected starting from the first.
    `static String` | `FETCH_OFFSET_PROPERTY` Defines the name of the property for the query `fetch offset`.
    `static boolean` | `FETCHING_DATA_ROWS_DEFAULT`
    `static String` | `FETCHING_DATA_ROWS_PROPERTY`
    `static int` | `PAGE_SIZE_DEFAULT` Defines default query page size, which is zero for no pagination.
    `static String` | `PAGE_SIZE_PROPERTY` Defines the name of the property for the query `page size`.
    `static int` | `STATEMENT_FETCH_SIZE_DEFAULT` Defines default query fetch start index, which is 0, meaning that matching rows selected starting from the first.
    `static String` | `STATEMENT_FETCH_SIZE_PROPERTY` Defines the name of the property for the query `fetch size`.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `String[]` | `getCacheGroups()` Returns an optional array of cache "groups".
    `String` | `getCacheKey()` Returns a String that uniquely identifies this query for the purposes of result caching.
    `QueryCacheStrategy` | `getCacheStrategy()` Returns a caching strategy for this query.
    `ClassDescriptor` | `getClassDescriptor()`
    `DataMap` | `getDataMap()` Returns a DataMap associated with a query or null if no such DataMap exists.
    `DbEntity` | `getDbEntity()` Returns a DbEntity associated with a query or null if no such entity exists.
    `int` | `getFetchLimit()` Returns the limit on the maximum number of records that can be returned by this query.
    `int` | `getFetchOffset()` Specifies a start of a range when fetching a subset of records.
    `ObjEntity` | `getObjEntity()` Returns an ObjEntity associated with a query or null if no such entity exists.
    `Query` | `getOrginatingQuery()` Returns a query that originated this query.
    `int` | `getPageSize()` Returns query page size.
    `Map<String,String>` | `getPathSplitAliases()` Returns a map of aliases vs.
    `PrefetchTreeNode` | `getPrefetchTree()` Returns a root node of prefetch tree used by this query, or null of no prefetches are configured.
    `Procedure` | `getProcedure()` Returns a Procedure associated with a query or null if no such procedure exists.
    `List<Object>` | `getResultSetMapping()` Returns an optional list of result set mapping hints.
    `int` | `getStatementFetchSize()`
    `boolean` | `isFetchingDataRows()` Returns `true` if this query should produce a list of data rows as opposed to DataObjects, `false` for DataObjects.
    `boolean` | `isRefreshingObjects()` Returns `true` if the query results should replace any currently cached values, returns `false` otherwise.

- - ### Field Detail

    - #### FETCH_LIMIT_PROPERTY

          static final String FETCH_LIMIT_PROPERTY

      Defines the name of the property for the query `fetch limit` .
      See Also:
        Constant Field Values

    - #### FETCH_LIMIT_DEFAULT

          static final int FETCH_LIMIT_DEFAULT

      Defines default query fetch limit, which is zero, meaning that all matching rows should be fetched.
      See Also:
        Constant Field Values

    - #### FETCH_OFFSET_PROPERTY

          static final String FETCH_OFFSET_PROPERTY

      Defines the name of the property for the query `fetch offset`.
      Since:
        3.0
      See Also:
        Constant Field Values

    - #### FETCH_OFFSET_DEFAULT

          static final int FETCH_OFFSET_DEFAULT

      Defines default query fetch start index, which is 0, meaning that matching rows selected starting from the first.
      Since:
        3.0
      See Also:
        Constant Field Values

    - #### PAGE_SIZE_PROPERTY

          static final String PAGE_SIZE_PROPERTY

      Defines the name of the property for the query `page size`.
      See Also:
        Constant Field Values

    - #### PAGE_SIZE_DEFAULT

          static final int PAGE_SIZE_DEFAULT

      Defines default query page size, which is zero for no pagination.
      See Also:
        Constant Field Values

    - #### FETCHING_DATA_ROWS_PROPERTY

          static final String FETCHING_DATA_ROWS_PROPERTY

      See Also:
        Constant Field Values

    - #### FETCHING_DATA_ROWS_DEFAULT

          static final boolean FETCHING_DATA_ROWS_DEFAULT

      See Also:
        Constant Field Values

    - #### CACHE_STRATEGY_PROPERTY

          static final String CACHE_STRATEGY_PROPERTY

      Since:
        3.0
      See Also:
        Constant Field Values

    - #### CACHE_GROUPS_PROPERTY

          static final String CACHE_GROUPS_PROPERTY

      Since:
        3.0
      See Also:
        Constant Field Values

    - #### STATEMENT_FETCH_SIZE_PROPERTY

          static final String STATEMENT_FETCH_SIZE_PROPERTY

      Defines the name of the property for the query `fetch size`.
      Since:
        3.0
      See Also:
        Constant Field Values

    - #### STATEMENT_FETCH_SIZE_DEFAULT

          static final int STATEMENT_FETCH_SIZE_DEFAULT

      Defines default query fetch start index, which is 0, meaning that matching rows selected starting from the first.
      Since:
        3.0
      See Also:
        Constant Field Values

  - ### Method Detail

    - #### getClassDescriptor

          ClassDescriptor getClassDescriptor()

      Since:
        3.0

    - #### getObjEntity

          ObjEntity getObjEntity()

      Returns an ObjEntity associated with a query or null if no such entity exists.

    - #### getDbEntity

          DbEntity getDbEntity()

      Returns a DbEntity associated with a query or null if no such entity exists.

    - #### getProcedure

          Procedure getProcedure()

      Returns a Procedure associated with a query or null if no such procedure exists.

    - #### getDataMap

          DataMap getDataMap()

      Returns a DataMap associated with a query or null if no such DataMap exists.

    - #### getCacheStrategy

          QueryCacheStrategy getCacheStrategy()

      Returns a caching strategy for this query.
      Since:
        3.0

    - #### getCacheKey

          String getCacheKey()

      Returns a String that uniquely identifies this query for the purposes of result caching. If null is returned, no caching is performed.

    - #### getCacheGroups

          String[] getCacheGroups()

      Returns an optional array of cache "groups". Cache groups allow to invalidate query caches in bulk on different events. Usually the first group in the array is considered to be the "main" group that is used for declarative cache invalidation with some cache providers.
      Since:
        3.0

    - #### isFetchingDataRows

          boolean isFetchingDataRows()

      Returns `true` if this query should produce a list of data rows as opposed to DataObjects, `false` for DataObjects. This is a hint to QueryEngine executing this query.

    - #### isRefreshingObjects

          boolean isRefreshingObjects()

      Returns `true` if the query results should replace any currently cached values, returns `false` otherwise. If `isFetchingDataRows()` returns `true`, this setting is not applicable and has no effect.

    - #### getPageSize

          int getPageSize()

      Returns query page size. Page size is a hint to Cayenne that query should be performed page by page, instead of retrieving all results at once. If the value returned is less than or equal to zero, no paging should occur.

    - #### getFetchOffset

          int getFetchOffset()

      Specifies a start of a range when fetching a subset of records.
      Since:
        3.0

    - #### getFetchLimit

          int getFetchLimit()

      Returns the limit on the maximum number of records that can be returned by this query. If the actual number of rows in the result exceeds the fetch limit, they will be discarded. One possible use of fetch limit is using it as a safeguard against large result sets that may lead to the application running out of memory, etc. If a fetch limit is greater or equal to zero, all rows will be returned.
      Returns:
        the limit on the maximum number of records that can be returned by this query

    - #### getOrginatingQuery

          Query getOrginatingQuery()

      Returns a query that originated this query. Originating query is a query whose result is needed to obtain the result of the query owning this metadata. Most often than not the returned value is null. One example of non-null originating query is a query for a range of objects in a previously fetched paginated list. The query that fetched the original paginated list is an "originated" query. It may be used to restore a list that got lost due to a cache overflow, etc.
      Since:
        3.0

    - #### getPrefetchTree

          PrefetchTreeNode getPrefetchTree()

      Returns a root node of prefetch tree used by this query, or null of no prefetches are configured.

    - #### getPathSplitAliases

          Map<String,String> getPathSplitAliases()

      Returns a map of aliases vs. expression subpaths that is used to build split joins.
      Since:
        3.0

    - #### getResultSetMapping

          List<Object> getResultSetMapping()

      Returns an optional list of result set mapping hints. Elements in the list can be either `EntityResultSegment` or `ScalarResultSegment`. The returned list can be null.
      Since:
        3.0

    - #### getStatementFetchSize

          int getStatementFetchSize()

      Returns:
        statement's fetch size
      Since:
        3.0

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