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/*
* Copyright 2004-2018 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.index;
import java.util.HashSet;
import org.h2.api.ErrorCode;
import org.h2.engine.Constants;
import org.h2.engine.DbObject;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.message.Trace;
import org.h2.result.Row;
import org.h2.result.SearchRow;
import org.h2.result.SortOrder;
import org.h2.schema.SchemaObjectBase;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.Table;
import org.h2.table.TableFilter;
import org.h2.util.StatementBuilder;
import org.h2.util.StringUtils;
import org.h2.value.Value;
import org.h2.value.ValueNull;
/**
* Most index implementations extend the base index.
*/
public abstract class BaseIndex extends SchemaObjectBase implements Index {
protected IndexColumn[] indexColumns;
protected Column[] columns;
protected int[] columnIds;
protected Table table;
protected IndexType indexType;
protected boolean isMultiVersion;
/**
* Initialize the base index.
*
* @param newTable the table
* @param id the object id
* @param name the index name
* @param newIndexColumns the columns that are indexed or null if this is
* not yet known
* @param newIndexType the index type
*/
protected void initBaseIndex(Table newTable, int id, String name,
IndexColumn[] newIndexColumns, IndexType newIndexType) {
initSchemaObjectBase(newTable.getSchema(), id, name, Trace.INDEX);
this.indexType = newIndexType;
this.table = newTable;
if (newIndexColumns != null) {
this.indexColumns = newIndexColumns;
columns = new Column[newIndexColumns.length];
int len = columns.length;
columnIds = new int[len];
for (int i = 0; i < len; i++) {
Column col = newIndexColumns[i].column;
columns[i] = col;
columnIds[i] = col.getColumnId();
}
}
}
/**
* Check that the index columns are not CLOB or BLOB.
*
* @param columns the columns
*/
protected static void checkIndexColumnTypes(IndexColumn[] columns) {
for (IndexColumn c : columns) {
int type = c.column.getType();
if (type == Value.CLOB || type == Value.BLOB) {
throw DbException.getUnsupportedException(
"Index on BLOB or CLOB column: " + c.column.getCreateSQL());
}
}
}
@Override
public String getDropSQL() {
return null;
}
/**
* Create a duplicate key exception with a message that contains the index
* name.
*
* @param key the key values
* @return the exception
*/
protected DbException getDuplicateKeyException(String key) {
String sql = getName() + " ON " + table.getSQL() +
"(" + getColumnListSQL() + ")";
if (key != null) {
sql += " VALUES " + key;
}
DbException e = DbException.get(ErrorCode.DUPLICATE_KEY_1, sql);
e.setSource(this);
return e;
}
@Override
public String getPlanSQL() {
return getSQL();
}
@Override
public void removeChildrenAndResources(Session session) {
table.removeIndex(this);
remove(session);
database.removeMeta(session, getId());
}
@Override
public boolean canFindNext() {
return false;
}
@Override
public boolean isFindUsingFullTableScan() {
return false;
}
@Override
public Cursor find(TableFilter filter, SearchRow first, SearchRow last) {
return find(filter.getSession(), first, last);
}
/**
* Find a row or a list of rows that is larger and create a cursor to
* iterate over the result. The base implementation doesn't support this
* feature.
*
* @param session the session
* @param higherThan the lower limit (excluding)
* @param last the last row, or null for no limit
* @return the cursor
* @throws DbException always
*/
@Override
public Cursor findNext(Session session, SearchRow higherThan, SearchRow last) {
throw DbException.throwInternalError(toString());
}
/**
* Calculate the cost for the given mask as if this index was a typical
* b-tree range index. This is the estimated cost required to search one
* row, and then iterate over the given number of rows.
*
* @param masks the IndexCondition search masks, one for each column in the
* table
* @param rowCount the number of rows in the index
* @param filters all joined table filters
* @param filter the current table filter index
* @param sortOrder the sort order
* @param isScanIndex whether this is a "table scan" index
* @param allColumnsSet the set of all columns
* @return the estimated cost
* 获取成本范围指数
*/
protected final long getCostRangeIndex(int[] masks, long rowCount,
TableFilter[] filters, int filter, SortOrder sortOrder,
boolean isScanIndex, HashSet allColumnsSet) {
rowCount += Constants.COST_ROW_OFFSET;
int totalSelectivity = 0;
long rowsCost = rowCount;
if (masks != null) {
for (int i = 0, len = columns.length; i < len; i++) {
Column column = columns[i];
int index = column.getColumnId();
int mask = masks[index];
if ((mask & IndexCondition.EQUALITY) == IndexCondition.EQUALITY) {
if (i == columns.length - 1 && getIndexType().isUnique()) {
rowsCost = 3;
break;
}
//百分比
totalSelectivity = 100 - ((100 - totalSelectivity) *
(100 - column.getSelectivity()) / 100);
//行数
long distinctRows = rowCount * totalSelectivity / 100;
if (distinctRows <= 0) {
distinctRows = 1;
}
rowsCost = 2 + Math.max(rowCount / distinctRows, 1);
} else if ((mask & IndexCondition.RANGE) == IndexCondition.RANGE) {
rowsCost = 2 + rowCount / 4;
break;
} else if ((mask & IndexCondition.START) == IndexCondition.START) {
rowsCost = 2 + rowCount / 3;
break;
} else if ((mask & IndexCondition.END) == IndexCondition.END) {
rowsCost = rowCount / 3;
break;
} else {
break;
}
}
}
// If the ORDER BY clause matches the ordering of this index,
// it will be cheaper than another index, so adjust the cost
// accordingly.
long sortingCost = 0;
if (sortOrder != null) {
sortingCost = 100 + rowCount / 10;
}
if (sortOrder != null && !isScanIndex) {
boolean sortOrderMatches = true;
int coveringCount = 0;
int[] sortTypes = sortOrder.getSortTypes();
TableFilter tableFilter = filters == null ? null : filters[filter];
for (int i = 0, len = sortTypes.length; i < len; i++) {
if (i >= indexColumns.length) {
// We can still use this index if we are sorting by more
// than it's columns, it's just that the coveringCount
// is lower than with an index that contains
// more of the order by columns.
break;
}
Column col = sortOrder.getColumn(i, tableFilter);
if (col == null) {
sortOrderMatches = false;
break;
}
IndexColumn indexCol = indexColumns[i];
if (!col.equals(indexCol.column)) {
sortOrderMatches = false;
break;
}
int sortType = sortTypes[i];
if (sortType != indexCol.sortType) {
sortOrderMatches = false;
break;
}
coveringCount++;
}
if (sortOrderMatches) {
// "coveringCount" makes sure that when we have two
// or more covering indexes, we choose the one
// that covers more.
sortingCost = 100 - coveringCount;
}
}
// If we have two indexes with the same cost, and one of the indexes can
// satisfy the query without needing to read from the primary table
// (scan index), make that one slightly lower cost.
boolean needsToReadFromScanIndex = true;
if (!isScanIndex && allColumnsSet != null && !allColumnsSet.isEmpty()) {
boolean foundAllColumnsWeNeed = true;
for (Column c : allColumnsSet) {
if (c.getTable() == getTable()) {
boolean found = false;
for (Column c2 : columns) {
if (c == c2) {
found = true;
break;
}
}
if (!found) {
foundAllColumnsWeNeed = false;
break;
}
}
}
if (foundAllColumnsWeNeed) {
needsToReadFromScanIndex = false;
}
}
long rc;
if (isScanIndex) {
rc = rowsCost + sortingCost + 20;
} else if (needsToReadFromScanIndex) {
rc = rowsCost + rowsCost + sortingCost + 20;
} else {
// The (20-x) calculation makes sure that when we pick a covering
// index, we pick the covering index that has the smallest number of
// columns (the more columns we have in index - the higher cost).
// This is faster because a smaller index will fit into fewer data
// blocks.
rc = rowsCost + sortingCost + columns.length;
}
return rc;
}
@Override
public int compareRows(SearchRow rowData, SearchRow compare) {
if (rowData == compare) {
return 0;
}
for (int i = 0, len = indexColumns.length; i < len; i++) {
int index = columnIds[i];
Value v1 = rowData.getValue(index);
Value v2 = compare.getValue(index);
if (v1 == null || v2 == null) {
// can't compare further
return 0;
}
int c = compareValues(v1, v2, indexColumns[i].sortType);
if (c != 0) {
return c;
}
}
return 0;
}
/**
* Check if this row may have duplicates with the same indexed values in the
* current compatibility mode. Duplicates with {@code NULL} values are
* allowed in some modes.
*
* @param searchRow
* the row to check
* @return {@code true} if specified row may have duplicates,
* {@code false otherwise}
*/
protected boolean mayHaveNullDuplicates(SearchRow searchRow) {
switch (database.getMode().uniqueIndexNullsHandling) {
case ALLOW_DUPLICATES_WITH_ANY_NULL:
for (int index : columnIds) {
if (searchRow.getValue(index) == ValueNull.INSTANCE) {
return true;
}
}
return false;
case ALLOW_DUPLICATES_WITH_ALL_NULLS:
for (int index : columnIds) {
if (searchRow.getValue(index) != ValueNull.INSTANCE) {
return false;
}
}
return true;
default:
return false;
}
}
/**
* Compare the positions of two rows.
*
* @param rowData the first row
* @param compare the second row
* @return 0 if both rows are equal, -1 if the first row is smaller,
* otherwise 1
*/
int compareKeys(SearchRow rowData, SearchRow compare) {
long k1 = rowData.getKey();
long k2 = compare.getKey();
if (k1 == k2) {
if (isMultiVersion) {
int v1 = rowData.getVersion();
int v2 = compare.getVersion();
return Integer.compare(v2, v1);
}
return 0;
}
return k1 > k2 ? 1 : -1;
}
private int compareValues(Value a, Value b, int sortType) {
if (a == b) {
return 0;
}
int comp = table.compareTypeSafe(a, b);
if ((sortType & SortOrder.DESCENDING) != 0) {
comp = -comp;
}
return comp;
}
@Override
public int getColumnIndex(Column col) {
for (int i = 0, len = columns.length; i < len; i++) {
if (columns[i].equals(col)) {
return i;
}
}
return -1;
}
@Override
public boolean isFirstColumn(Column column) {
return column.equals(columns[0]);
}
/**
* Get the list of columns as a string.
*
* @return the list of columns
*/
private String getColumnListSQL() {
StatementBuilder buff = new StatementBuilder();
for (IndexColumn c : indexColumns) {
buff.appendExceptFirst(", ");
buff.append(c.getSQL());
}
return buff.toString();
}
@Override
public String getCreateSQLForCopy(Table targetTable, String quotedName) {
StringBuilder buff = new StringBuilder("CREATE ");
buff.append(indexType.getSQL());
buff.append(' ');
if (table.isHidden()) {
buff.append("IF NOT EXISTS ");
}
buff.append(quotedName);
buff.append(" ON ").append(targetTable.getSQL());
if (comment != null) {
buff.append(" COMMENT ").append(StringUtils.quoteStringSQL(comment));
}
buff.append('(').append(getColumnListSQL()).append(')');
return buff.toString();
}
@Override
public String getCreateSQL() {
return getCreateSQLForCopy(table, getSQL());
}
@Override
public IndexColumn[] getIndexColumns() {
return indexColumns;
}
@Override
public Column[] getColumns() {
return columns;
}
@Override
public IndexType getIndexType() {
return indexType;
}
@Override
public int getType() {
return DbObject.INDEX;
}
@Override
public Table getTable() {
return table;
}
@Override
public void commit(int operation, Row row) {
// nothing to do
}
void setMultiVersion(boolean multiVersion) {
this.isMultiVersion = multiVersion;
}
@Override
public Row getRow(Session session, long key) {
throw DbException.getUnsupportedException(toString());
}
@Override
public boolean isHidden() {
return table.isHidden();
}
@Override
public boolean isRowIdIndex() {
return false;
}
@Override
public boolean canScan() {
return true;
}
@Override
public void setSortedInsertMode(boolean sortedInsertMode) {
// ignore
}
@Override
public IndexLookupBatch createLookupBatch(TableFilter[] filters, int filter) {
// Lookup batching is not supported.
return null;
}
}
