From 93143369ce58750a77a3cf4402de7406670e430c Mon Sep 17 00:00:00 2001
From: Michael Kolupaev <mkolupaev@yandex-team.ru>
Date: Thu, 13 Dec 2012 09:32:08 +0000
Subject: [PATCH] clickhouse: added support for non-UInt32 sampling columns
 [#6201].

---
 dbms/src/Storages/StorageMergeTree.cpp | 73 ++++++++++++++------------
 1 file changed, 38 insertions(+), 35 deletions(-)

diff --git a/dbms/src/Storages/StorageMergeTree.cpp b/dbms/src/Storages/StorageMergeTree.cpp
index 9c4c1be70b..7bea70a380 100644
--- a/dbms/src/Storages/StorageMergeTree.cpp
+++ b/dbms/src/Storages/StorageMergeTree.cpp
@@ -825,9 +825,7 @@ BlockInputStreams StorageMergeTree::read(
 
 	/// Семплирование.
 	Names column_names_to_read = column_names_to_return;
-	size_t count_limit = std::numeric_limits<size_t>::max();
-	bool sample_by_value = false;
-	UInt64 sample_column_value_limit = 0;
+	UInt64 sampling_column_value_limit = 0;
 	typedef Poco::SharedPtr<ASTFunction> ASTFunctionPtr;
 	ASTFunctionPtr filter_function;
 	ExpressionPtr filter_expression;
@@ -835,31 +833,51 @@ BlockInputStreams StorageMergeTree::read(
 	ASTSelectQuery & select = *dynamic_cast<ASTSelectQuery*>(&*query);
 	if (select.sample_size)
 	{
-		double size = boost::apply_visitor(FieldVisitorConvertToNumber<double>(), dynamic_cast<ASTLiteral*>(&*select.sample_size)->value);
+		double size = boost::apply_visitor(FieldVisitorConvertToNumber<double>(), dynamic_cast<ASTLiteral&>(*select.sample_size).value);
 		if (size < 0)
 			throw Exception("Negative sample size", ErrorCodes::ARGUMENT_OUT_OF_BOUND);
 		if (size > 1)
 		{
-			count_limit = boost::apply_visitor(FieldVisitorConvertToNumber<UInt64>(), dynamic_cast<ASTLiteral*>(&*select.sample_size)->value);
+			size_t requested_count = boost::apply_visitor(FieldVisitorConvertToNumber<UInt64>(), dynamic_cast<ASTLiteral&>(*select.sample_size).value);
+			
+			/// Узнаем количество строк в таблице.
+			size_t total_count = 0;
+			{
+				Poco::ScopedLock<Poco::FastMutex> lock(data_parts_mutex);
+				
+				for (DataParts::iterator it = data_parts.begin(); it != data_parts.end(); ++it)
+					total_count += (*it)->size;
+			}
+			total_count *= index_granularity;
+			
+			size = std::min(1., static_cast<double>(requested_count) / total_count);
 		}
+		
+		UInt64 sampling_column_max = 0;
+		DataTypePtr type = Expression(sampling_expression, context).getReturnTypes()[0];
+		
+		if (type->getName() == "UInt64")
+			sampling_column_max = std::numeric_limits<UInt64>::max();
+		else if (type->getName() == "UInt32")
+			sampling_column_max = std::numeric_limits<UInt32>::max();
+		else if (type->getName() == "UInt16")
+			sampling_column_max = std::numeric_limits<UInt16>::max();
+		else if (type->getName() == "UInt8")
+			sampling_column_max = std::numeric_limits<UInt8>::max();
 		else
-		{
-			sample_by_value = true;
-			sample_column_value_limit = static_cast<UInt64>(size * std::numeric_limits<UInt32>::max());
-			if (!key_condition.addCondition(sampling_expression->getColumnName(),
-				Range::RightBounded(sample_column_value_limit, true)))
-				throw Exception("Invalid sampling column in storage parameters", ErrorCodes::ILLEGAL_COLUMN);
-		}
-	}
-	
-	if (sample_by_value)
-	{
-		/// Выражение для фильтрации: sampling_column_name <= sample_column_value_limit
+			throw Exception("Invalid sampling column type in storage parameters: " + type->getName() + ". Must be unsigned integer type.", ErrorCodes::ILLEGAL_TYPE_OF_COLUMN_FOR_FILTER);
+
+		sampling_column_value_limit = static_cast<UInt64>(size * sampling_column_max);
+		if (!key_condition.addCondition(sampling_expression->getColumnName(),
+			Range::RightBounded(sampling_column_value_limit, true)))
+			throw Exception("Sampling column not in primary key", ErrorCodes::ILLEGAL_COLUMN);
+
+		/// Выражение для фильтрации: sampling_expression <= sampling_column_value_limit
 
 		ASTPtr filter_function_args = new ASTExpressionList;
 		filter_function_args->children.push_back(sampling_expression);
-		filter_function_args->children.push_back(new ASTLiteral(StringRange(), sample_column_value_limit));
-		
+		filter_function_args->children.push_back(new ASTLiteral(StringRange(), sampling_column_value_limit));
+
 		filter_function = new ASTFunction;
 		filter_function->name = "lessOrEquals";
 		filter_function->arguments = filter_function_args;
@@ -891,7 +909,6 @@ BlockInputStreams StorageMergeTree::read(
 	RangesInDataParts parts_with_ranges;
 	
 	/// Найдем, какой диапазон читать из каждого куска.
-	size_t mark_count_limit = (count_limit - 1) / index_granularity + 1;
 	size_t sum_marks = 0;
 	size_t sum_ranges = 0;
 	for (size_t i = 0; i < parts.size(); ++i)
@@ -910,21 +927,7 @@ BlockInputStreams StorageMergeTree::read(
 			for (size_t j = 0; j < ranges.ranges.size(); ++j)
 			{
 				sum_marks += ranges.ranges[j].end - ranges.ranges[j].begin;
-				
-				/// Если нашли достаточно строк.
-				if (sum_marks >= mark_count_limit)
-				{
-					MarkRanges & new_ranges = parts_with_ranges.back().ranges;
-					/// Обрежем этот отрезок.
-					new_ranges[j].end -= mark_count_limit - sum_marks;
-					/// Удалим вссе последующие отрезки.
-					new_ranges.erase(new_ranges.begin() + j + 1, new_ranges.end());
-				}
 			}
-			
-			/// Если нашли достаточно строк, дальше можено не смотреть.
-			if (sum_marks * index_granularity >= count_limit)
-				break;
 		}
 	}
 	
@@ -933,7 +936,7 @@ BlockInputStreams StorageMergeTree::read(
 	
 	BlockInputStreams res = spreadMarkRangesAmongThreads(parts_with_ranges, threads, column_names_to_read, max_block_size);
 	
-	if (sample_by_value)
+	if (select.sample_size)
 	{
 		for (size_t i = 0; i < res.size(); ++i)
 		{
-- 
GitLab