Package org.h2.command.query

Class Query

java.lang.Object
org.h2.command.Prepared
org.h2.command.query.Query
Direct Known Subclasses:
Select, SelectUnion, TableValueConstructor
public abstract class Query extends Prepared
Represents a SELECT statement (simple, or union).

  • Method Details

    • setNeverLazy

      public void setNeverLazy(boolean b)

    • isNeverLazy

      public boolean isNeverLazy()

    • isUnion

      public abstract boolean isUnion()
      Check if this is a UNION query.
      Returns:
      true if this is a UNION query

    • queryMeta

      public ResultInterface queryMeta()
      Description copied from class: Prepared
      Get an empty result set containing the meta data.
      Specified by:
      queryMeta in class Prepared
      Returns:
      the result set

    • queryWithoutCache

      protected abstract ResultInterface queryWithoutCache(long limit, ResultTarget target)
      Execute the query without checking the cache. If a target is specified, the results are written to it, and the method returns null. If no target is specified, a new LocalResult is created and returned.
      Parameters:
      limit - the limit as specified in the JDBC method call
      target - the target to write results to
      Returns:
      the result

    • init

      public abstract void init()
      Initialize the query.

    • prepare

      public final void prepare()
      Description copied from class: Prepared
      Prepare this statement.
      Overrides:
      prepare in class Prepared

    • prepareExpressions

      public abstract void prepareExpressions()

    • preparePlan

      public abstract void preparePlan()

    • getExpressions

      public ArrayList<Expression> getExpressions()
      The the list of select expressions. This may include invisible expressions such as order by expressions.
      Returns:
      the list of expressions

    • getCost

      public abstract double getCost()
      Calculate the cost to execute this query.
      Returns:
      the cost

    • getCostAsExpression

      public int getCostAsExpression()
      Calculate the cost when used as a subquery. This method returns a value between 10 and 1000000, to ensure adding other values can't result in an integer overflow.
      Returns:
      the estimated cost as an integer

    • getTables

      public abstract HashSet<Table> getTables()
      Get all tables that are involved in this query.
      Returns:
      the set of tables

    • setOrder

      public void setOrder(ArrayList<QueryOrderBy> order)
      Set the order by list.
      Parameters:
      order - the order by list

    • hasOrder

      public boolean hasOrder()
      Whether the query has an order.
      Returns:
      true if it has

    • getForUpdate

      public ForUpdate getForUpdate()
      Returns FOR UPDATE clause, if any.
      Returns:
      FOR UPDATE clause or null

    • setForUpdate

      public abstract void setForUpdate(ForUpdate forUpdate)
      Set the FOR UPDATE clause.
      Parameters:
      forUpdate - the new FOR UPDATE clause

    • getColumnCount

      public int getColumnCount()
      Get the column count of this query.
      Returns:
      the column count

    • getRowDataType

      public TypeInfo getRowDataType()
      Returns data type of rows.
      Returns:
      data type of rows

    • mapColumns

      public abstract void mapColumns(ColumnResolver resolver, int level, boolean outer)
      Map the columns to the given column resolver.
      Parameters:
      resolver - the resolver
      level - the subquery level (0 is the top level query, 1 is the first subquery level)
      outer - whether this method was called from the outer query

    • setEvaluatable

      public abstract void setEvaluatable(TableFilter tableFilter, boolean b)
      Change the evaluatable flag. This is used when building the execution plan.
      Parameters:
      tableFilter - the table filter
      b - the new value

    • addGlobalCondition

      public abstract void addGlobalCondition(Parameter param, int columnId, int comparisonType)
      Add a condition to the query. This is used for views.
      Parameters:
      param - the parameter
      columnId - the column index (0 meaning the first column)
      comparisonType - the comparison type

    • allowGlobalConditions

      public abstract boolean allowGlobalConditions()
      Check whether adding condition to the query is allowed. This is not allowed for views that have an order by and a limit, as it would affect the returned results.
      Returns:
      true if adding global conditions is allowed

    • isEverything

      public abstract boolean isEverything(ExpressionVisitor visitor)
      Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.
      Parameters:
      visitor - the visitor
      Returns:
      if the criteria can be fulfilled

    • isReadOnly

      public boolean isReadOnly()
      Description copied from class: Prepared
      Check if this command is read only.
      Overrides:
      isReadOnly in class Prepared
      Returns:
      true if it is

    • updateAggregate

      public abstract void updateAggregate(SessionLocal s, int stage)
      Update all aggregate function values.
      Parameters:
      s - the session
      stage - select stage

    • fireBeforeSelectTriggers

      public abstract void fireBeforeSelectTriggers()
      Call the before triggers on all tables.

    • setDistinctIfPossible

      public void setDistinctIfPossible()
      Set the distinct flag only if it is possible, may be used as a possible optimization only.

    • isStandardDistinct

      public boolean isStandardDistinct()
      Returns:
      whether this query is a plain DISTINCT query

    • isAnyDistinct

      public boolean isAnyDistinct()
      Returns:
      whether this query is a DISTINCT or DISTINCT ON (...) query

    • isRandomAccessResult

      public boolean isRandomAccessResult()
      Returns whether results support random access.
      Returns:
      whether results support random access

    • setRandomAccessResult

      public void setRandomAccessResult(boolean b)
      Whether results need to support random access.
      Parameters:
      b - the new value

    • isQuery

      public boolean isQuery()
      Description copied from class: Prepared
      Check if this object is a query.
      Overrides:
      isQuery in class Prepared
      Returns:
      true if it is

    • isTransactional

      public boolean isTransactional()
      Description copied from class: Prepared
      Check if this command is transactional. If it is not, then it forces the current transaction to commit.
      Specified by:
      isTransactional in class Prepared
      Returns:
      true if it is

    • disableCache

      public void disableCache()
      Disable caching of result sets.

    • query

      public final ResultInterface query(long maxrows)
      Description copied from class: Prepared
      Execute the query.
      Overrides:
      query in class Prepared
      Parameters:
      maxrows - the maximum number of rows to return
      Returns:
      the result set

    • query

      public final ResultInterface query(long limit, ResultTarget target)
      Execute the query, writing the result to the target result.
      Parameters:
      limit - the maximum number of rows to return
      target - the target result (null will return the result)
      Returns:
      the result set (if the target is not set).

    • exists

      public final boolean exists()
      Execute the EXISTS predicate over the query.
      Returns:
      EXISTS predicate result

    • getType

      public int getType()
      Description copied from class: Prepared
      Get the command type as defined in CommandInterface
      Specified by:
      getType in class Prepared
      Returns:
      the statement type

    • setOffset

      public void setOffset(Expression offset)

    • getOffset

      public Expression getOffset()

    • setFetch

      public void setFetch(Expression fetch)

    • getFetch

      public Expression getFetch()

    • setFetchPercent

      public void setFetchPercent(boolean fetchPercent)

    • isFetchPercent

      public boolean isFetchPercent()

    • setWithTies

      public void setWithTies(boolean withTies)

    • isWithTies

      public boolean isWithTies()

    • getMaxDataModificationId

      public final long getMaxDataModificationId()

    • getOuterQueryScope

      public QueryScope getOuterQueryScope()
      Returns the scope of the outer query.
      Returns:
      the scope of the outer query

    • setOuterQueryScope

      public void setOuterQueryScope(QueryScope outerQueryScope)
      Sets the scope of the outer query.
      Parameters:
      outerQueryScope - the scope of the outer query

    • setWithClause

      public void setWithClause(LinkedHashMap<String,Table> withClause)
      Sets the WITH clause of this query.
      Parameters:
      withClause - the WITH clause of this query

    • writeWithList

      protected void writeWithList(StringBuilder builder, int sqlFlags)

    • toTable

      public Table toTable(String alias, Column[] columnTemplates, ArrayList<Parameter> parameters, boolean forCreateView, Query topQuery)
      Converts this query to a table or a view.
      Parameters:
      alias - alias name for the view
      columnTemplates - column templates, or null
      parameters - the parameters
      forCreateView - if true, a system session will be used for the view
      topQuery - the top level query
      Returns:
      the table or the view

    • collectDependencies

      public void collectDependencies(HashSet<DbObject> dependencies)
      Description copied from class: Prepared
      Find and collect all DbObjects, this Prepared depends on.
      Overrides:
      collectDependencies in class Prepared
      Parameters:
      dependencies - collection of dependencies to populate

    • isConstantQuery

      public boolean isConstantQuery()
      Check if this query will always return the same value and has no side effects.
      Returns:
      if this query will always return the same value and has no side effects.

    • getIfSingleRow

      public Expression getIfSingleRow()
      If this query is determined as a single-row query, returns a replacement expression.
      Returns:
      the expression, or null

    • isRetryable

      public boolean isRetryable()
      Description copied from class: Prepared
      Returns is this command can be repeated again on locking failure.
      Overrides:
      isRetryable in class Prepared
      Returns:
      is this command can be repeated again on locking failure