Package org.eclipse.persistence.queries

Class ReadQuery

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable
    Direct Known Subclasses:
    DataReadQuery, ObjectBuildingQuery
    public abstract class ReadQuery
extends DatabaseQuery

    Purpose: Abstract class for all read queries.

    Responsibilities:

    • Caches result of query if flag is set.
    See Also:
    Serialized Form
    Author:
    Yvon Lavoie
    Since:
    TOPLink/Java 1.0

    • Field Detail

      • maxRows

        protected int maxRows
        Used for retrieve limited rows through the query.

      • firstResult

        protected int firstResult
        Used to start query results at a specific result

      • queryId

        protected long queryId

      • fetchSize

        protected int fetchSize
        Used to set statement fetch size

      • queryResultCachingPolicy

        protected QueryResultsCachePolicy queryResultCachingPolicy
        Used to specify how query results are cached

      • temporaryCachedQueryResults

        protected transient java.lang.Object temporaryCachedQueryResults
        Optimization: temporarily stores cached query results while they are being built in a cloned query

      • maxResults

        protected int maxResults
        Stores the JPA maxResult settings for a NamedQuery

      • allowQueryResultsCacheValidation

        protected boolean allowQueryResultsCacheValidation
        Flag that allows query result cache validation or not.

    • Constructor Detail

      • ReadQuery

        public ReadQuery()
        PUBLIC: Initialize the state of the query

    • Method Detail

      • buildObject

        public java.lang.Object buildObject​(org.eclipse.persistence.internal.sessions.AbstractRecord row)
        INTERNAL: By default return the row. Used by cursored stream.

      • cacheQueryResults

        public void cacheQueryResults()
        ADVANCED:

        This method will instruct the query to cache the results returned by its next execution. All subsequent executions of this query will return this cached result set even if new query parameters are specified. This method provides a performance enhancement for queries known to always return the same result set. Oracle recommends that you use this method only for such queries.

        To disable this behavior, call doNotCacheQueryResults() or setQueryResultsCachePolicy(org.eclipse.persistence.queries.QueryResultsCachePolicy) passing in null.

      • cacheResult

        public abstract void cacheResult​(java.lang.Object object)
        INTERNAL:

        This method is called by the object builder when building an original. It will cause the original to be cached in the query results if the query is set to do so.

      • clonedQueryExecutionComplete

        protected void clonedQueryExecutionComplete​(DatabaseQuery query,
                                            org.eclipse.persistence.internal.sessions.AbstractSession session)
        INTERNAL Used to give the subclasses opportunity to copy aspects of the cloned query to the original query.
        Overrides:
        clonedQueryExecutionComplete in class DatabaseQuery

      • clearQueryResults

        public void clearQueryResults​(org.eclipse.persistence.internal.sessions.AbstractSession session)
        PUBLIC: Clears the current cached results, the next execution with read from the database.

      • doNotCacheQueryResults

        public void doNotCacheQueryResults()
        ADVANCED:

        This method will instruct the query not to cache results. All subsequent executions return result sets according to the current configuration of query parameters. After calling this method, any previously cached result set will be discarded the next time the query is executed.

        To enable this behavior, call cacheQueryResults() or setQueryResultsCachePolicy(org.eclipse.persistence.queries.QueryResultsCachePolicy) passing in a valid QueryResultsCachePolicy.

        Note: If this method is called on a query that initially cached query results, clearQueryResults(Session) should also be called. Otherwise, the results of this query will remain in the cache and cause extra memory use

      • getFirstResult

        public int getFirstResult()
        PUBLIC: Return the value that will be set for the firstResult in the returned result set

      • getQueryId

        public long getQueryId()
        INTERNAL: This method is used to get the time in millis that this query is being executed at. it is set just prior to executing the SQL and will be used to determine which objects should be refreshed. CR #4365 CR #2698903 ... instead of using millis we will now use id's instead. Method renamed appropriately.

      • getInternalMax

        public int getInternalMax()
        INTERNAL: returns the JPA max results that may have been set on a NamedQuery
        Returns:
        the maxResults

      • getMaxRows

        public int getMaxRows()
        PUBLIC: Return the limit for the maximum number of rows that any ResultSet can contain to the given number.

      • getFetchSize

        public int getFetchSize()
        PUBLIC: Return the fetchSize setting that this query will set on the JDBC Statement NB - a value of zero means that no call to statement.setFetchSize() will be made.

      • getQueryResults

        protected java.lang.Object getQueryResults​(org.eclipse.persistence.internal.sessions.AbstractSession session)
        INTERNAL: To any user of this object with some knowledge of what the query's results may contain. Return the results of the query. If the query has never been executed, or does not cache results, the results will be null.

      • getQueryResults

        protected java.lang.Object getQueryResults​(org.eclipse.persistence.internal.sessions.AbstractSession session,
                                           boolean checkExpiry)
        INTERNAL: To any user of this object with some knowledge of what the query's results may contain. Return the results of the query. If the query has never been executed, or does not cache results, the results will be null.

      • getQueryResults

        protected java.lang.Object getQueryResults​(org.eclipse.persistence.internal.sessions.AbstractSession session,
                                           org.eclipse.persistence.internal.sessions.AbstractRecord row,
                                           boolean checkExpiry)
        INTERNAL: To any user of this object with some knowledge of what the query's results may contain. Return the results of the query. If the query has never been executed, or does not cache results, the results will be null.

      • getTemporaryCachedQueryResults

        public java.lang.Object getTemporaryCachedQueryResults()
        INTERNAL: Get results from the remporary cache. Used when caching query results on a clone so they can be copied to the original query

      • isDefaultPropertiesQuery

        public boolean isDefaultPropertiesQuery()
        INTERNAL: Return true if the query uses default properties. This is used to determine if this query is cacheable. i.e. does not use any properties that may conflict with another query with the same EJBQL or selection criteria.
        Overrides:
        isDefaultPropertiesQuery in class DatabaseQuery

      • isReadQuery

        public boolean isReadQuery()
        PUBLIC: Return if this is a read query.
        Overrides:
        isReadQuery in class DatabaseQuery

      • copyFromQuery

        public void copyFromQuery​(DatabaseQuery query)
        INTERNAL: Copy all setting from the query. This is used to morph queries from one type to the other. By default this calls prepareFromQuery, but additional properties may be required to be copied as prepareFromQuery only copies properties that affect the SQL.
        Overrides:
        copyFromQuery in class DatabaseQuery

      • prepare

        protected void prepare()
                throws QueryException
        INTERNAL: This is different from 'prepareForExecution' in that this is called on the original query, and the other is called on the copy of the query. This query is copied for concurrency so this prepare can only setup things that will apply to any future execution of this query. Clear the query cache when a query is prepared.
        Overrides:
        prepare in class DatabaseQuery
        Throws:
        QueryException

      • setFirstResult

        public void setFirstResult​(int firstResult)
        PUBLIC: Used to set the first result in any result set that is returned for this query. On supported database platforms this will cause the query to issue specific SQL that avoids selecting the firstResult number of rows. Otherwise by it will use the JDBC absolute to skip the firstResult number of rows.

      • setQueryId

        public void setQueryId​(long id)
        INTERNAL: This method is used to set the current system time in millis that this query is being executed at. it is set just prior to executing the SQL and will be used to determine which objects should be refreshed. CR #4365 CR #2698903 ... instead of using millis we will now use id's instead. Method renamed appropriately.

      • setInternalMax

        public void setInternalMax​(int max)
        INTERNAL: sets the JPA max results that may have been set on a NamedQuery

      • setMaxRows

        public void setMaxRows​(int maxRows)
        PUBLIC: Used to set the limit for the maximum number of rows that any ResultSet can contain to the given number. This method should only be set once per query. To change the max rows use another query. This method limits the number of candidate results returned to TopLink that can be used to build objects

      • setFetchSize

        public void setFetchSize​(int fetchSize)
        PUBLIC: Set the fetchSize setting that this query will set on the JDBC Statement NB - a value of zero means that no call to statement.setFetchSize() will be made.

      • setQueryResults

        protected void setQueryResults​(java.lang.Object resultFromQuery,
                               org.eclipse.persistence.internal.sessions.AbstractRecord row,
                               org.eclipse.persistence.internal.sessions.AbstractSession session)
        INTERNAL: Set the cached results of the query. This will only be set if the query caches results.

      • shouldCacheQueryResults

        public boolean shouldCacheQueryResults()
        PUBLIC: Return if the query should cache the results of the next execution or not.

      • setTemporaryCachedQueryResults

        public void setTemporaryCachedQueryResults​(java.lang.Object queryResults)
        INTERNAL: Put results in the temporary cache. Used when caching query results on a clone so they can be copied to the original query

      • shouldAllowQueryResultsCacheValidation

        public boolean shouldAllowQueryResultsCacheValidation()

      • setAllowQueryResultsCacheValidation

        public void setAllowQueryResultsCacheValidation​(boolean allowQueryResultsCacheValidation)