/*
* 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 org.h2.expression;
import java.util.HashMap;
import org.h2.api.ErrorCode;
import org.h2.command.Parser;
import org.h2.command.dml.Select;
import org.h2.command.dml.SelectListColumnResolver;
import org.h2.engine.Database;
import org.h2.engine.Session;
import org.h2.index.IndexCondition;
import org.h2.message.DbException;
import org.h2.schema.Constant;
import org.h2.schema.Schema;
import org.h2.table.Column;
import org.h2.table.ColumnResolver;
import org.h2.table.Table;
import org.h2.table.TableFilter;
import org.h2.value.Value;
import org.h2.value.ValueBoolean;
/**
* A expression that represents a column of a table or view.
*/
public class ExpressionColumn extends Expression {
private final Database database;
private final String schemaName;
private final String tableAlias;
private final String columnName;
private ColumnResolver columnResolver;
private int queryLevel;
private Column column;
private boolean evaluatable;
private Select select; //我加上的
public ExpressionColumn(Database database, Column column) {
this.database = database;
this.column = column;
this.schemaName = null;
this.tableAlias = null;
this.columnName = null;
}
//对于SELECT public.t.id FROM ExpressionColumnTest as t
//schemaName = public
//tableAlias = t
//columnName = id
public ExpressionColumn(Database database, String schemaName, String tableAlias, String columnName) {
this.database = database;
this.schemaName = schemaName;
this.tableAlias = tableAlias;
this.columnName = columnName;
}
@Override
public String getSQL() {
String sql;
boolean quote = database.getSettings().databaseToUpper;
if (column != null) {
sql = column.getSQL();
} else {
sql = quote ? Parser.quoteIdentifier(columnName) : columnName;
}
if (tableAlias != null) {
String a = quote ? Parser.quoteIdentifier(tableAlias) : tableAlias;
sql = a + "." + sql;
}
if (schemaName != null) {
String s = quote ? Parser.quoteIdentifier(schemaName) : schemaName;
sql = s + "." + sql;
}
return sql;
}
public TableFilter getTableFilter() {
return columnResolver == null ? null : columnResolver.getTableFilter();
}
@Override
public void mapColumns(ColumnResolver resolver, int level) {
//我加上的
if (select == null)
select = resolver.getSelect();
if (tableAlias != null && !database.equalsIdentifiers(
tableAlias, resolver.getTableAlias())) {
return;
}
if (schemaName != null && !database.equalsIdentifiers(
schemaName, resolver.getSchemaName())) {
return;
}
for (Column col : resolver.getColumns()) {
String n = col.getName();
if (database.equalsIdentifiers(columnName, n)) {
mapColumn(resolver, col, level);
return;
}
}
if (database.equalsIdentifiers(Column.ROWID, columnName)) {
Column col = resolver.getRowIdColumn();
if (col != null) {
mapColumn(resolver, col, level);
return;
}
}
Column[] columns = resolver.getSystemColumns();
for (int i = 0; columns != null && i < columns.length; i++) {
Column col = columns[i];
if (database.equalsIdentifiers(columnName, col.getName())) {
mapColumn(resolver, col, level);
return;
}
}
}
private void mapColumn(ColumnResolver resolver, Column col, int level) {
if (this.columnResolver == null) {
queryLevel = level;
column = col;
this.columnResolver = resolver;
} else if (queryLevel == level && this.columnResolver != resolver) {
if (resolver instanceof SelectListColumnResolver) {
// ignore - already mapped, that's ok
} else {
throw DbException.get(ErrorCode.AMBIGUOUS_COLUMN_NAME_1, columnName);
}
}
}
//列名不存在的检查是放在这里做
//sql = "select name,id3 from mytable order by name";
//Column "ID3" not found;
@Override
public Expression optimize(Session session) { //在之前已调用mapColumns了，确保columnResolver被适当赋值了
if (columnResolver == null) {
Schema schema = session.getDatabase().findSchema(
tableAlias == null ? session.getCurrentSchemaName() : tableAlias);
if (schema != null) {
Constant constant = schema.findConstant(columnName);
if (constant != null) {
return constant.getValue(); //对于常量字段的优化是直接返回ValueExpression
}
}
//我加上的
// if (select != null) {
// for (Expression e : select.getExpressions()) {
// if (database.equalsIdentifiers(columnName, e.getAlias()))
// return e.getNonAliasExpression().optimize(session);
// }
// }
String name = columnName;
if (tableAlias != null) {
name = tableAlias + "." + name;
if (schemaName != null) {
name = schemaName + "." + name;
}
}
throw DbException.get(ErrorCode.COLUMN_NOT_FOUND_1, name);
}
return columnResolver.optimize(this, column);
}
@Override
public void updateAggregate(Session session) {
Value now = columnResolver.getValue(column);
Select select = columnResolver.getSelect();
if (select == null) {
throw DbException.get(ErrorCode.MUST_GROUP_BY_COLUMN_1, getSQL());
}
HashMap<Expression, Object> values = select.getCurrentGroup();
if (values == null) {
// this is a different level (the enclosing query)
return;
}
Value v = (Value) values.get(this);
if (v == null) {
values.put(this, now); //如果不是非group by字段，则只保留第一次出现的值
} else {
// 如果不注释掉，这样的SQL会出错
// SELECT id/3 AS A, COUNT(*) FROM mytable GROUP BY A HAVING A>=0
// if (!database.areEqual(now, v)) {
// throw DbException.get(ErrorCode.MUST_GROUP_BY_COLUMN_1, getSQL());
// }
}
}
@Override
public Value getValue(Session session) {
Select select = columnResolver.getSelect();
if (select != null) {
HashMap<Expression, Object> values = select.getCurrentGroup();
if (values != null) {
Value v = (Value) values.get(this);
if (v != null) {
return v;
}
}
}
Value value = columnResolver.getValue(column);
if (value == null) {
columnResolver.getValue(column);
throw DbException.get(ErrorCode.MUST_GROUP_BY_COLUMN_1, getSQL());
}
return value;
}
@Override
public int getType() {
return column.getType();
}
@Override
public void setEvaluatable(TableFilter tableFilter, boolean b) {
if (columnResolver != null && tableFilter == columnResolver.getTableFilter()) {
evaluatable = b;
}
}
public Column getColumn() {
return column;
}
@Override
public int getScale() {
return column.getScale();
}
@Override
public long getPrecision() {
return column.getPrecision();
}
@Override
public int getDisplaySize() {
return column.getDisplaySize();
}
public String getOriginalColumnName() {
return columnName;
}
public String getOriginalTableAliasName() {
return tableAlias;
}
@Override
public String getColumnName() {
return columnName != null ? columnName : column.getName();
}
@Override
public String getSchemaName() {
Table table = column.getTable();
return table == null ? null : table.getSchema().getName();
}
@Override
public String getTableName() {
Table table = column.getTable();
return table == null ? null : table.getName();
}
@Override
public String getAlias() {
if (column != null) {
return column.getName();
}
if (tableAlias != null) {
return tableAlias + "." + columnName;
}
return columnName;
}
@Override
public boolean isAutoIncrement() {
return column.getSequence() != null;
}
@Override
public int getNullable() {
return column.isNullable() ? Column.NULLABLE : Column.NOT_NULLABLE;
}
@Override
public boolean isEverything(ExpressionVisitor visitor) {
switch (visitor.getType()) {
case ExpressionVisitor.OPTIMIZABLE_MIN_MAX_COUNT_ALL:
return false;
case ExpressionVisitor.READONLY:
case ExpressionVisitor.DETERMINISTIC:
case ExpressionVisitor.QUERY_COMPARABLE:
return true;
case ExpressionVisitor.INDEPENDENT:
return this.queryLevel < visitor.getQueryLevel();
case ExpressionVisitor.EVALUATABLE:
// if the current value is known (evaluatable set)
// or if this columns belongs to a 'higher level' query and is
// therefore just a parameter
if (database.getSettings().nestedJoins) {
if (visitor.getQueryLevel() < this.queryLevel) {
return true;
}
if (getTableFilter() == null) {
return false;
}
return getTableFilter().isEvaluatable();
}
return evaluatable || visitor.getQueryLevel() < this.queryLevel;
case ExpressionVisitor.SET_MAX_DATA_MODIFICATION_ID:
visitor.addDataModificationId(column.getTable().getMaxDataModificationId());
return true;
case ExpressionVisitor.NOT_FROM_RESOLVER:
return columnResolver != visitor.getResolver();
case ExpressionVisitor.GET_DEPENDENCIES:
if (column != null) {
visitor.addDependency(column.getTable());
}
return true;
case ExpressionVisitor.GET_COLUMNS:
visitor.addColumn(column);
return true;
default:
throw DbException.throwInternalError("type=" + visitor.getType());
}
}
@Override
public int getCost() {
return 2;
}
@Override
public void createIndexConditions(Session session, TableFilter filter) {
//如
//create table IF NOT EXISTS DeleteTest(id int, name varchar(500), b boolean)
//delete from DeleteTest where b
//按字段b删除，实际上就是删除b=true的记录
//如果没有为字段b建立索引，就在org.h2.table.TableFilter.prepare()中删除这个无用条件
TableFilter tf = getTableFilter();
if (filter == tf && column.getType() == Value.BOOLEAN) {
IndexCondition cond = IndexCondition.get(
Comparison.EQUAL, this, ValueExpression.get(
ValueBoolean.get(true)));
filter.addIndexCondition(cond);
}
}
@Override
public Expression getNotIfPossible(Session session) {
return new Comparison(session, Comparison.EQUAL, this,
ValueExpression.get(ValueBoolean.get(false)));
}
}