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/*
* Copyright 2004-2022 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.index;
import java.util.ArrayList;
import java.util.Arrays;
import org.h2.api.ErrorCode;
import org.h2.command.query.AllColumnsForPlan;
import org.h2.engine.Constants;
import org.h2.engine.DbObject;
import org.h2.engine.SessionLocal;
import org.h2.message.DbException;
import org.h2.message.Trace;
import org.h2.result.Row;
import org.h2.result.RowFactory;
import org.h2.result.SearchRow;
import org.h2.result.SortOrder;
import org.h2.schema.SchemaObject;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.Table;
import org.h2.table.TableFilter;
import org.h2.util.StringUtils;
import org.h2.value.CompareMode;
import org.h2.value.DataType;
import org.h2.value.Value;
import org.h2.value.ValueNull;
/**
* An index. Indexes are used to speed up searching data.
*/
public abstract class Index extends SchemaObject {
/**
* Check that the index columns are not CLOB or BLOB.
*
* @param columns the columns
*/
protected static void checkIndexColumnTypes(IndexColumn[] columns) {
for (IndexColumn c : columns) {
if (!DataType.isIndexable(c.column.getType())) {
throw DbException.getUnsupportedException("Index on column: " + c.column.getCreateSQL());
}
}
}
/**
* Columns of this index.
*/
protected IndexColumn[] indexColumns;
/**
* Table columns used in this index.
*/
protected Column[] columns;
/**
* Identities of table columns.
*/
protected int[] columnIds;
/**
* Count of unique columns. Unique columns, if any, are always first columns
* in the lists.
*/
protected final int uniqueColumnColumn;
/**
* The table.
*/
protected final Table table;
/**
* The index type.
*/
protected final IndexType indexType;
private final RowFactory rowFactory;
private final RowFactory uniqueRowFactory;
/**
* Initialize the 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 uniqueColumnCount count of unique columns
* @param newIndexType the index type
*/
protected Index(Table newTable, int id, String name, IndexColumn[] newIndexColumns, int uniqueColumnCount,
IndexType newIndexType) {
super(newTable.getSchema(), id, name, Trace.INDEX);
this.uniqueColumnColumn = uniqueColumnCount;
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();
}
}
RowFactory databaseRowFactory = database.getRowFactory();
CompareMode compareMode = database.getCompareMode();
Column[] tableColumns = table.getColumns();
rowFactory = databaseRowFactory.createRowFactory(database, compareMode, database, tableColumns,
newIndexType.isScan() ? null : newIndexColumns, true);
RowFactory uniqueRowFactory;
if (uniqueColumnCount > 0) {
if (newIndexColumns == null || uniqueColumnCount == newIndexColumns.length) {
uniqueRowFactory = rowFactory;
} else {
uniqueRowFactory = databaseRowFactory.createRowFactory(database, compareMode, database, tableColumns,
Arrays.copyOf(newIndexColumns, uniqueColumnCount), true);
}
} else {
uniqueRowFactory = null;
}
this.uniqueRowFactory = uniqueRowFactory;
}
@Override
public final int getType() {
return DbObject.INDEX;
}
@Override
public void removeChildrenAndResources(SessionLocal session) {
table.removeIndex(this);
remove(session);
database.removeMeta(session, getId());
}
@Override
public final boolean isHidden() {
return table.isHidden();
}
@Override
public String getCreateSQLForCopy(Table targetTable, String quotedName) {
StringBuilder builder = new StringBuilder("CREATE ");
builder.append(indexType.getSQL());
builder.append(' ');
if (table.isHidden()) {
builder.append("IF NOT EXISTS ");
}
builder.append(quotedName);
builder.append(" ON ");
targetTable.getSQL(builder, DEFAULT_SQL_FLAGS);
if (comment != null) {
builder.append(" COMMENT ");
StringUtils.quoteStringSQL(builder, comment);
}
return getColumnListSQL(builder, DEFAULT_SQL_FLAGS).toString();
}
/**
* Get the list of columns as a string.
*
* @param sqlFlags formatting flags
* @return the list of columns
*/
private StringBuilder getColumnListSQL(StringBuilder builder, int sqlFlags) {
builder.append('(');
int length = indexColumns.length;
if (uniqueColumnColumn > 0 && uniqueColumnColumn < length) {
IndexColumn.writeColumns(builder, indexColumns, 0, uniqueColumnColumn, sqlFlags).append(") INCLUDE(");
IndexColumn.writeColumns(builder, indexColumns, uniqueColumnColumn, length, sqlFlags);
} else {
IndexColumn.writeColumns(builder, indexColumns, 0, length, sqlFlags);
}
return builder.append(')');
}
@Override
public String getCreateSQL() {
return getCreateSQLForCopy(table, getSQL(DEFAULT_SQL_FLAGS));
}
/**
* Get the message to show in a EXPLAIN statement.
*
* @return the plan
*/
public String getPlanSQL() {
return getSQL(TRACE_SQL_FLAGS | ADD_PLAN_INFORMATION);
}
/**
* Close this index.
*
* @param session the session used to write data
*/
public abstract void close(SessionLocal session);
/**
* Add a row to the index.
*
* @param session the session to use
* @param row the row to add
*/
public abstract void add(SessionLocal session, Row row);
/**
* Remove a row from the index.
*
* @param session the session
* @param row the row
*/
public abstract void remove(SessionLocal session, Row row);
/**
* Update index after row change.
*
* @param session the session
* @param oldRow row before the update
* @param newRow row after the update
*/
public void update(SessionLocal session, Row oldRow, Row newRow) {
remove(session, oldRow);
add(session, newRow);
}
/**
* Returns {@code true} if {@code find()} implementation performs scan over all
* index, {@code false} if {@code find()} performs the fast lookup.
*
* @return {@code true} if {@code find()} implementation performs scan over all
* index, {@code false} if {@code find()} performs the fast lookup
*/
public boolean isFindUsingFullTableScan() {
return false;
}
/**
* Find a row or a list of rows and create a cursor to iterate over the
* result.
*
* @param session the session
* @param first the first row, or null for no limit
* @param last the last row, or null for no limit
* @return the cursor to iterate over the results
*/
public abstract Cursor find(SessionLocal session, SearchRow first, SearchRow last);
/**
* Estimate the cost to search for rows given the search mask.
* There is one element per column in the search mask.
* For possible search masks, see IndexCondition.
*
* @param session the session
* @param masks per-column comparison bit masks, null means 'always false',
* see constants in IndexCondition
* @param filters all joined table filters
* @param filter the current table filter index
* @param sortOrder the sort order
* @param allColumnsSet the set of all columns
* @return the estimated cost
*/
public abstract double getCost(SessionLocal session, int[] masks, TableFilter[] filters, int filter,
SortOrder sortOrder, AllColumnsForPlan allColumnsSet);
/**
* Remove the index.
*
* @param session the session
*/
public abstract void remove(SessionLocal session);
/**
* Remove all rows from the index.
*
* @param session the session
*/
public abstract void truncate(SessionLocal session);
/**
* Check if the index can directly look up the lowest or highest value of a
* column.
*
* @return true if it can
*/
public boolean canGetFirstOrLast() {
return false;
}
/**
* Check if the index can get the next higher value.
*
* @return true if it can
*/
public boolean canFindNext() {
return false;
}
/**
* Find a row or a list of rows that is larger and create a cursor to
* iterate over the result.
*
* @param session the session
* @param higherThan the lower limit (excluding)
* @param last the last row, or null for no limit
* @return the cursor
*/
public Cursor findNext(SessionLocal session, SearchRow higherThan, SearchRow last) {
throw DbException.getInternalError(toString());
}
/**
* Find the first (or last) value of this index. The cursor returned is
* positioned on the correct row, or on null if no row has been found.
*
* @param session the session
* @param first true if the first (lowest for ascending indexes) or last
* value should be returned
* @return a cursor (never null)
*/
public Cursor findFirstOrLast(SessionLocal session, boolean first) {
throw DbException.getInternalError(toString());
}
/**
* Check if the index needs to be rebuilt.
* This method is called after opening an index.
*
* @return true if a rebuild is required.
*/
public abstract boolean needRebuild();
/**
* Get the row count of this table, for the given session.
*
* @param session the session
* @return the row count
*/
public abstract long getRowCount(SessionLocal session);
/**
* Get the approximated row count for this table.
*
* @param session the session
* @return the approximated row count
*/
public abstract long getRowCountApproximation(SessionLocal session);
/**
* Get the used disk space for this index.
*
* @return the estimated number of bytes
*/
public long getDiskSpaceUsed() {
return 0L;
}
/**
* Compare 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
*/
public final 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;
}
private int compareValues(Value a, Value b, int sortType) {
if (a == b) {
return 0;
}
boolean aNull = a == ValueNull.INSTANCE;
if (aNull || b == ValueNull.INSTANCE) {
return table.getDatabase().getDefaultNullOrdering().compareNull(aNull, sortType);
}
int comp = table.compareValues(database, a, b);
if ((sortType & SortOrder.DESCENDING) != 0) {
comp = -comp;
}
return comp;
}
/**
* Get the index of a column in the list of index columns
*
* @param col the column
* @return the index (0 meaning first column)
*/
public int getColumnIndex(Column col) {
for (int i = 0, len = columns.length; i < len; i++) {
if (columns[i].equals(col)) {
return i;
}
}
return -1;
}
/**
* Check if the given column is the first for this index
*
* @param column the column
* @return true if the given columns is the first
*/
public boolean isFirstColumn(Column column) {
return column.equals(columns[0]);
}
/**
* Get the indexed columns as index columns (with ordering information).
*
* @return the index columns
*/
public final IndexColumn[] getIndexColumns() {
return indexColumns;
}
/**
* Get the indexed columns.
*
* @return the columns
*/
public final Column[] getColumns() {
return columns;
}
/**
* Returns count of unique columns. Unique columns, if any, are always first
* columns in the lists. Unique indexes may have additional indexed
* non-unique columns.
*
* @return count of unique columns, or 0 if index isn't unique
*/
public final int getUniqueColumnCount() {
return uniqueColumnColumn;
}
/**
* Get the index type.
*
* @return the index type
*/
public final IndexType getIndexType() {
return indexType;
}
/**
* Get the table on which this index is based.
*
* @return the table
*/
public Table getTable() {
return table;
}
/**
* Get the row with the given key.
*
* @param session the session
* @param key the unique key
* @return the row
*/
public Row getRow(SessionLocal session, long key) {
throw DbException.getUnsupportedException(toString());
}
/**
* Does this index support lookup by row id?
*
* @return true if it does
*/
public boolean isRowIdIndex() {
return false;
}
/**
* Can this index iterate over all rows?
*
* @return true if it can
*/
public boolean canScan() {
return true;
}
/**
* Create a duplicate key exception with a message that contains the index
* name.
*
* @param key the key values
* @return the exception
*/
public DbException getDuplicateKeyException(String key) {
StringBuilder builder = new StringBuilder();
getSQL(builder, TRACE_SQL_FLAGS).append(" ON ");
table.getSQL(builder, TRACE_SQL_FLAGS);
getColumnListSQL(builder, TRACE_SQL_FLAGS);
if (key != null) {
builder.append(" VALUES ").append(key);
}
DbException e = DbException.get(ErrorCode.DUPLICATE_KEY_1, builder.toString());
e.setSource(this);
return e;
}
/**
* Get "PRIMARY KEY ON <table> [(column)]".
*
* @param mainIndexColumn the column index
* @return the message
*/
protected StringBuilder getDuplicatePrimaryKeyMessage(int mainIndexColumn) {
StringBuilder builder = new StringBuilder("PRIMARY KEY ON ");
table.getSQL(builder, TRACE_SQL_FLAGS);
if (mainIndexColumn >= 0 && mainIndexColumn < indexColumns.length) {
builder.append('(');
indexColumns[mainIndexColumn].getSQL(builder, TRACE_SQL_FLAGS).append(')');
}
return builder;
}
/**
* 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
*/
protected final long getCostRangeIndex(int[] masks, long rowCount, TableFilter[] filters, int filter,
SortOrder sortOrder, boolean isScanIndex, AllColumnsForPlan allColumnsSet) {
rowCount += Constants.COST_ROW_OFFSET;
int totalSelectivity = 0;
long rowsCost = rowCount;
if (masks != null) {
int i = 0, len = columns.length;
boolean tryAdditional = false;
while (i < len) {
Column column = columns[i++];
int index = column.getColumnId();
int mask = masks[index];
if ((mask & IndexCondition.EQUALITY) == IndexCondition.EQUALITY) {
if (i > 0 && i == uniqueColumnColumn) {
rowsCost = 3;
break;
}
totalSelectivity = 100 - ((100 - totalSelectivity) *
(100 - column.getSelectivity()) / 100);
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 + rowsCost / 4;
tryAdditional = true;
break;
} else if ((mask & IndexCondition.START) == IndexCondition.START) {
rowsCost = 2 + rowsCost / 3;
tryAdditional = true;
break;
} else if ((mask & IndexCondition.END) == IndexCondition.END) {
rowsCost = rowsCost / 3;
tryAdditional = true;
break;
} else {
if (mask == 0) {
// Adjust counter of used columns (i)
i--;
}
break;
}
}
// Some additional columns can still be used
if (tryAdditional) {
while (i < len && masks[columns[i].getColumnId()] != 0) {
i++;
rowsCost--;
}
}
// Increase cost of indexes with additional unused columns
rowsCost += len - i;
}
// 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.getSortTypesWithNullOrdering();
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;
if (!isScanIndex && allColumnsSet != null) {
needsToReadFromScanIndex = false;
ArrayList foundCols = allColumnsSet.get(getTable());
if (foundCols != null) {
int main = table.getMainIndexColumn();
loop: for (Column c : foundCols) {
int id = c.getColumnId();
if (id == SearchRow.ROWID_INDEX || id == main) {
continue;
}
for (Column c2 : columns) {
if (c == c2) {
continue loop;
}
}
needsToReadFromScanIndex = true;
break;
}
}
} else {
needsToReadFromScanIndex = true;
}
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;
}
/**
* 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}
*/
public final boolean mayHaveNullDuplicates(SearchRow searchRow) {
switch (database.getMode().uniqueIndexNullsHandling) {
case ALLOW_DUPLICATES_WITH_ANY_NULL:
for (int i = 0; i < uniqueColumnColumn; i++) {
int index = columnIds[i];
if (searchRow.getValue(index) == ValueNull.INSTANCE) {
return true;
}
}
return false;
case ALLOW_DUPLICATES_WITH_ALL_NULLS:
for (int i = 0; i < uniqueColumnColumn; i++) {
int index = columnIds[i];
if (searchRow.getValue(index) != ValueNull.INSTANCE) {
return false;
}
}
return true;
default:
return false;
}
}
public RowFactory getRowFactory() {
return rowFactory;
}
public RowFactory getUniqueRowFactory() {
return uniqueRowFactory;
}
}
