studio.raptor.sqlparser.fast.expression.Expression Maven / Gradle / Ivy
/*
* Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package studio.raptor.sqlparser.fast.expression;
import studio.raptor.sqlparser.fast.table.ColumnResolver;
import studio.raptor.sqlparser.fast.util.StringUtils;
import studio.raptor.sqlparser.fast.value.Value;
/**
* An expression is a operation, a value, or a function in a query.
*/
public abstract class Expression {
/**
* Map the columns of the resolver to expression columns.
*
* @param resolver the column resolver
* @param level the subquery nesting level
*/
public abstract void mapColumns(ColumnResolver resolver, int level);
/**
* Return the resulting value for the current row.
*
* @return the result
*/
public abstract Value getValue();
/**
* Return the data type. The data type may not be known before the
* optimization phase.
*
* @return the type
*/
public abstract int getType();
/**
* Try to optimize the expression.
*
* @return the optimized expression
*/
public abstract Expression optimize();
/**
* Get the SQL statement of this expression.
* This may not always be the original SQL statement,
* specially after optimization.
*
* @return the SQL statement
*/
public abstract String getSQL();
/**
* Check if this expression and all sub-expressions can fulfill a criteria.
* If any part returns false, the result is false.
*
* @param visitor the visitor
* @return if the criteria can be fulfilled
*/
public abstract boolean isEverything(ExpressionVisitor visitor);
/**
* Check if this expression will always return the same value.
*
* @return if the expression is constant
*/
public boolean isConstant() {
return false;
}
/**
* Is the value of a parameter set.
*
* @return true if set
*/
public boolean isValueSet() {
return false;
}
/**
* Get the column name or alias name of this expression.
*
* @return the column name
*/
public String getColumnName() {
return getAlias();
}
/**
* Get the table name, or null
*
* @return the table name
*/
public String getTableName() {
return null;
}
/**
* Get the table alias name or null
* if this expression does not represent a column.
*
* @return the table alias name
*/
public String getTableAlias() {
return null;
}
/**
* Get the alias name of a column or SQL expression
* if it is not an aliased expression.
*
* @return the alias name
*/
public String getAlias() {
return StringUtils.unEnclose(getSQL());
}
/**
* Only returns true if the expression is a wildcard.
*
* @return if this expression is a wildcard
*/
public boolean isWildcard() {
return false;
}
/**
* Returns the main expression, skipping aliases.
*
* @return the expression
*/
public Expression getNonAliasExpression() {
return this;
}
/**
* Convert this expression to a String.
*
* @return the string representation
*/
@Override
public String toString() {
return getSQL();
}
}