phoenix 如何优化成使用索引进行查询源码分析

phoenix 如何优化成使用索引进行查询源码分析

在 phoenix 生成执行计划时，最后会进行执行计划的优化，在优化过程中，会根据当前的sql中有没有hint的

提示使用索引，或者查询中用到了索引字段，也会自动转换成用索引表进行关联查询。

在下面的方法当中，会根据已有的执行计划，进行优化

QueryOptimizer.getApplicablePlans

//根据当前的数据执行计划，优化成用索引进行数据的查询
private List<QueryPlan> getApplicablePlans(QueryPlan dataPlan, PhoenixStatement statement, List<? extends PDatum> targetColumns, ParallelIteratorFactory parallelIteratorFactory, boolean stopAtBestPlan) throws SQLException {
SelectStatement select = (SelectStatement)dataPlan.getStatement();
// Exit early if we have a point lookup as we can't get better than that
if (!useIndexes
|| (dataPlan.getContext().getScanRanges().isPointLookup() && stopAtBestPlan)) {
return Collections.singletonList(dataPlan);
}
// For single query tuple projection, indexes are inherited from the original table to the projected
// table; otherwise not. So we pass projected table here, which is enough to tell if this is from a
// single query or a part of join query.
//判断是否使用索引进行处理
List<PTable>indexes = Lists.newArrayList(dataPlan.getContext().getResolver().getTables().get(0).getTable().getIndexes());
if (indexes.isEmpty() || dataPlan.isDegenerate() || dataPlan.getTableRef().hasDynamicCols() || select.getHint().hasHint(Hint.NO_INDEX)) {
return Collections.singletonList(dataPlan);
}

// The targetColumns is set for UPSERT SELECT to ensure that the proper type conversion takes place.
// For a SELECT, it is empty. In this case, we want to set the targetColumns to match the projection
// from the dataPlan to ensure that the metadata for when an index is used matches the metadata for
// when the data table is used.
if (targetColumns.isEmpty()) {
List<? extends ColumnProjector> projectors = dataPlan.getProjector().getColumnProjectors();
List<PDatum> targetDatums = Lists.newArrayListWithExpectedSize(projectors.size());
for (ColumnProjector projector : projectors) {
targetDatums.add(projector.getExpression());
}
targetColumns = targetDatums;
}
//在里面转换一下方式
SelectStatement translatedIndexSelect = IndexStatementRewriter.translate(select, FromCompiler.getResolver(dataPlan.getTableRef()));
List<QueryPlan> plans = Lists.newArrayListWithExpectedSize(1 + indexes.size());
plans.add(dataPlan);
//拿出指定的hint的查询方式
QueryPlan hintedPlan = getHintedQueryPlan(statement, translatedIndexSelect, indexes, targetColumns, parallelIteratorFactory, plans);
if (hintedPlan != null) {
if (stopAtBestPlan) {
return Collections.singletonList(hintedPlan);
}
plans.add(0, hintedPlan);
}

for (PTable index : indexes) {
//当没有指定hint的方式时
QueryPlan plan = addPlan(statement, translatedIndexSelect, index, targetColumns, parallelIteratorFactory, dataPlan, false);
if (plan != null) {
// Query can't possibly return anything so just return this plan.
if (plan.isDegenerate()) {
return Collections.singletonList(plan);
}
plans.add(plan);
}
}

return hintedPlan == null ? orderPlansBestToWorst(select, plans) : plans;
}

可以看到，上面根据当前是否具有hints提示和物理表是否创建了索引进行执行计划的优化

当使用hints提示时，会调用下面的方法

private static QueryPlan getHintedQueryPlan(PhoenixStatement statement, SelectStatement select, List<PTable> indexes, List<? extends PDatum> targetColumns, ParallelIteratorFactory parallelIteratorFactory, List<QueryPlan> plans) throws SQLException {
QueryPlan dataPlan = plans.get(0);
//查询语句中是否有hints
String indexHint = select.getHint().getHint(Hint.INDEX);
if (indexHint == null) {
return null;
}
int startIndex = 0;
String alias = dataPlan.getTableRef().getTableAlias();
//对hint的解释 (mytable myindex)
String prefix = HintNode.PREFIX + (alias == null ? dataPlan.getTableRef().getTable().getName().getString() : alias) + HintNode.SEPARATOR;
while (startIndex < indexHint.length()) {
startIndex = indexHint.indexOf(prefix, startIndex);
if (startIndex < 0) {
return null;
}
startIndex += prefix.length();
boolean done = false; // true when SUFFIX found
while (startIndex < indexHint.length() && !done) {
int endIndex;
int endIndex1 = indexHint.indexOf(HintNode.SEPARATOR, startIndex);
int endIndex2 = indexHint.indexOf(HintNode.SUFFIX, startIndex);
if (endIndex1 < 0 && endIndex2 < 0) { // Missing SUFFIX shouldn't happen
endIndex = indexHint.length();
} else if (endIndex1 < 0) {
done = true;
endIndex = endIndex2;
} else if (endIndex2 < 0) {
endIndex = endIndex1;
} else {
endIndex = Math.min(endIndex1, endIndex2);
done = endIndex2 == endIndex;
}
String indexName = indexHint.substring(startIndex, endIndex);
int indexPos = getIndexPosition(indexes, indexName);
if (indexPos >= 0) {
// Hinted index is applicable, so return it's index
PTable index = indexes.get(indexPos);
indexes.remove(indexPos);
//对hints解释成功了
QueryPlan plan = addPlan(statement, select, index, targetColumns, parallelIteratorFactory, dataPlan, true);
if (plan != null) {
return plan;
}
}
startIndex = endIndex + 1;
}
}
return null;
}

上面解释出Sql中的查询的hints的提示，使用指定的索引进行查询，生成执行计划

//增加索引执行计划
private static QueryPlan addPlan(PhoenixStatement statement, SelectStatement select, PTable index, List<? extends PDatum> targetColumns, ParallelIteratorFactory parallelIteratorFactory, QueryPlan dataPlan, boolean isHinted) throws SQLException {
int nColumns = dataPlan.getProjector().getColumnCount();
String tableAlias = dataPlan.getTableRef().getTableAlias();
String alias = tableAlias==null ? null : '"' + tableAlias + '"'; // double quote in case it's case sensitive
String schemaName = index.getParentSchemaName().getString();
schemaName = schemaName.length() == 0 ? null :  '"' + schemaName + '"';

String tableName = '"' + index.getTableName().getString() + '"';
TableNode table = FACTORY.namedTable(alias, FACTORY.table(schemaName, tableName));
//生成对新索引表的查询计划
SelectStatement indexSelect = FACTORY.select(select, table);
ColumnResolver resolver = FromCompiler.getResolverForQuery(indexSelect, statement.getConnection());
// We will or will not do tuple projection according to the data plan.
boolean isProjected = dataPlan.getContext().getResolver().getTables().get(0).getTable().getType() == PTableType.PROJECTED;
// Check index state of now potentially updated index table to make sure it's active
//当前索引状态是正常的
if (PIndexState.ACTIVE.equals(resolver.getTables().get(0).getTable().getIndexState())) {
try {
// translate nodes that match expressions that are indexed to the associated column parse node
indexSelect = ParseNodeRewriter.rewrite(indexSelect, new  IndexExpressionParseNodeRewriter(index, statement.getConnection(), indexSelect.getUdfParseNodes()));
QueryCompiler compiler = new QueryCompiler(statement, indexSelect, resolver, targetColumns, parallelIteratorFactory, dataPlan.getContext().getSequenceManager(), isProjected);
//生成新的查询计划
QueryPlan plan = compiler.compile();
// If query doesn't have where clause and some of columns to project are missing
// in the index then we need to get missing columns from main table for each row in
// local index. It's like full scan of both local index and data table which is inefficient.
// Then we don't use the index. If all the columns to project are present in the index
// then we can use the index even the query doesn't have where clause.
if (index.getIndexType() == IndexType.LOCAL && indexSelect.getWhere() == null
&& !plan.getContext().getDataColumns().isEmpty()) {
return null;
}
// Checking number of columns handles the wildcard cases correctly, as in that case the index
// must contain all columns from the data table to be able to be used.
//用到的索引是活动状态，并且要查询的字段全在索引表，就返回
if (plan.getTableRef().getTable().getIndexState() == PIndexState.ACTIVE) {
if (plan.getProjector().getColumnCount() == nColumns) {
//最后生成新的索引表的查询计划是可以的
return plan;
} else if (index.getIndexType() == IndexType.GLOBAL) {
//当依赖于全局索引表，但是全局表中又找不到要查询的字段，就出错,到下面通过子查询转换进行查询
throw new ColumnNotFoundException("*");
}
}
} catch (ColumnNotFoundException e) {
/* Means that a column is being used that's not in our index.
* Since we currently don't keep stats, we don't know the selectivity of the index.
* For now, if this is a hinted plan, we will try rewriting the query as a subquery;
* otherwise we just don't use this index (as opposed to trying to join back from
* the index table to the data table.
*/
//当查询的字段不在索引表时，要关联到数据表进行数据的查询,通过子查询的方式进行数据的查询
SelectStatement dataSelect = (SelectStatement)dataPlan.getStatement();
ParseNode where = dataSelect.getWhere();
if (isHinted && where != null) {
StatementContext context = new StatementContext(statement, resolver);
WhereConditionRewriter whereRewriter = new WhereConditionRewriter(FromCompiler.getResolver(dataPlan.getTableRef()), context);
where = where.accept(whereRewriter);
if (where != null) {
//这个是原始的数据表
PTable dataTable = dataPlan.getTableRef().getTable();
List<PColumn> pkColumns = dataTable.getPKColumns();
//要进行索引查询的字段
List<AliasedNode> aliasedNodes = Lists.<AliasedNode>newArrayListWithExpectedSize(pkColumns.size());
List<ParseNode> nodes = Lists.<ParseNode>newArrayListWithExpectedSize(pkColumns.size());
boolean isSalted = dataTable.getBucketNum() != null;
boolean isTenantSpecific = dataTable.isMultiTenant() && statement.getConnection().getTenantId() != null;
int posOffset = (isSalted ? 1 : 0) + (isTenantSpecific ? 1 : 0);
for (int i = posOffset; i < pkColumns.size(); i++) {
PColumn column = pkColumns.get(i);
String indexColName = IndexUtil.getIndexColumnName(column);
ParseNode indexColNode = new ColumnParseNode(null, '"' + indexColName + '"', indexColName);
PDataType indexColType = IndexUtil.getIndexColumnDataType(column);
PDataType dataColType = column.getDataType();
if (indexColType != dataColType) {
indexColNode = FACTORY.cast(indexColNode, dataColType, null, null);
}
aliasedNodes.add(FACTORY.aliasedNode(null, indexColNode));
nodes.add(new ColumnParseNode(null, '"' + column.getName().getString() + '"'));
}
//生成一个内部子查询
SelectStatement innerSelect = FACTORY.select(indexSelect.getFrom(), indexSelect.getHint(), false, aliasedNodes, where, null, null, null, null, indexSelect.getBindCount(), false, indexSelect.hasSequence(), Collections.<SelectStatement>emptyList(), indexSelect.getUdfParseNodes());
ParseNode outerWhere = FACTORY.in(nodes.size() == 1 ? nodes.get(0) : FACTORY.rowValueConstructor(nodes), FACTORY.subquery(innerSelect, false), false, true);
ParseNode extractedCondition = whereRewriter.getExtractedCondition();
if (extractedCondition != null) {
outerWhere = FACTORY.and(Lists.newArrayList(outerWhere, extractedCondition));
}
HintNode hint = HintNode.combine(HintNode.subtract(indexSelect.getHint(), new Hint[] {Hint.INDEX, Hint.NO_CHILD_PARENT_JOIN_OPTIMIZATION}), FACTORY.hint("NO_INDEX"));
SelectStatement query = FACTORY.select(dataSelect, hint, outerWhere);
ColumnResolver queryResolver = FromCompiler.getResolverForQuery(query, statement.getConnection());
//生成索引的子查询
query = SubqueryRewriter.transform(query, queryResolver, statement.getConnection());
queryResolver = FromCompiler.getResolverForQuery(query, statement.getConnection());
query = StatementNormalizer.normalize(query, queryResolver);
QueryPlan plan = new QueryCompiler(statement, query, queryResolver, targetColumns, parallelIteratorFactory, dataPlan.getContext().getSequenceManager(), isProjected).compile();
return plan;
}
}
}
}
return null;
}

假如没有进行hints的提示，但是物理表建立了索引，则下面根据查询的物理表的字段中是否全部在索引表当中，如果是

则直接查询索引表返回数据，否则使用索引表作为子查询的方式，进行关联查询，从而使用索引表进行数据的快速查询

总结

根据当前是否具有hints提示，通过hints提示中使用的索引表进行查询

根据物理表建立的索引，当查询字段全在索引表时，使用索引表进行直接查询，否则生成子查询对索引表进行查询