lbug 0.16.1

An in-process property graph database management system built for query speed and scalability
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257

#include "planner/join_order/cardinality_estimator.h"

#include "binder/expression/property_expression.h"
#include "catalog/catalog.h"
#include "catalog/catalog_entry/table_catalog_entry.h"
#include "main/client_context.h"
#include "planner/join_order/join_order_util.h"
#include "planner/operator/logical_aggregate.h"
#include "planner/operator/logical_hash_join.h"
#include "planner/operator/scan/logical_scan_node_table.h"
#include "storage/storage_manager.h"
#include "storage/table/node_table.h"
#include "storage/table/rel_table.h"

using namespace lbug::binder;
using namespace lbug::common;
using namespace lbug::transaction;

namespace lbug {
namespace planner {

static cardinality_t atLeastOne(uint64_t x) {
    return x == 0 ? 1 : x;
}

void CardinalityEstimator::init(const QueryGraph& queryGraph) {
    for (auto i = 0u; i < queryGraph.getNumQueryNodes(); ++i) {
        init(*queryGraph.getQueryNode(i));
    }
    for (uint64_t i = 0u; i < queryGraph.getNumQueryRels(); ++i) {
        auto rel = queryGraph.getQueryRel(i);
        if (QueryRelTypeUtils::isRecursive(rel->getRelType())) {
            auto recursiveInfo = rel->getRecursiveInfo();
            init(*recursiveInfo->node);
        }
    }
}

void CardinalityEstimator::init(const NodeExpression& node) {
    auto key = node.getInternalID()->getUniqueName();
    cardinality_t numNodes = 0u;
    auto storageManager = storage::StorageManager::Get(*context);
    auto transaction = transaction::Transaction::Get(*context);
    for (auto entry : node.getEntries()) {
        // Skip foreign tables - they don't have storage in the local database
        if (entry->getType() == catalog::CatalogEntryType::FOREIGN_TABLE_ENTRY) {
            continue;
        }
        auto tableID = entry->getTableID();
        auto stats =
            storageManager->getTable(tableID)->cast<storage::NodeTable>().getStats(transaction);
        numNodes += stats.getTableCard();
        if (!nodeTableStats.contains(tableID)) {
            nodeTableStats.insert({tableID, std::move(stats)});
        }
    }
    if (!nodeIDName2dom.contains(key)) {
        nodeIDName2dom.insert({key, numNodes});
    }
}

void CardinalityEstimator::rectifyCardinality(const Expression& nodeID, cardinality_t card) {
    DASSERT(nodeIDName2dom.contains(nodeID.getUniqueName()));
    auto newCard = std::min(nodeIDName2dom.at(nodeID.getUniqueName()), card);
    nodeIDName2dom[nodeID.getUniqueName()] = newCard;
}

cardinality_t CardinalityEstimator::getNodeIDDom(const std::string& nodeIDName) const {
    DASSERT(nodeIDName2dom.contains(nodeIDName));
    return nodeIDName2dom.at(nodeIDName);
}

uint64_t CardinalityEstimator::estimateScanNode(const LogicalOperator& op) const {
    const auto& scan = op.constCast<const LogicalScanNodeTable&>();
    switch (scan.getScanType()) {
    case LogicalScanNodeTableType::PRIMARY_KEY_SCAN:
        return 1;
    default:
        return atLeastOne(getNodeIDDom(scan.getNodeID()->getUniqueName()));
    }
}

uint64_t CardinalityEstimator::estimateAggregate(const LogicalAggregate& op) const {
    // TODO(Royi) we can use HLL to better estimate the number of distinct keys here
    return op.getKeys().empty() ? 1 : op.getChild(0)->getCardinality();
}

cardinality_t CardinalityEstimator::multiply(double extensionRate, cardinality_t card) const {
    return atLeastOne(extensionRate * card);
}

uint64_t CardinalityEstimator::estimateHashJoin(
    const std::vector<binder::expression_pair>& joinConditions, const LogicalOperator& probeOp,
    const LogicalOperator& buildOp) const {
    if (LogicalHashJoin::isNodeIDOnlyJoin(joinConditions)) {
        cardinality_t denominator = 1u;
        auto joinKeys = LogicalHashJoin::getJoinNodeIDs(joinConditions);
        for (auto& joinKey : joinKeys) {
            if (nodeIDName2dom.contains(joinKey->getUniqueName())) {
                denominator *= getNodeIDDom(joinKey->getUniqueName());
            }
        }
        return atLeastOne(probeOp.getCardinality() *
                          JoinOrderUtil::getJoinKeysFlatCardinality(joinKeys, buildOp) /
                          atLeastOne(denominator));
    } else {
        // Naively estimate the cardinality if the join is non-ID based
        cardinality_t estCardinality = probeOp.getCardinality() * buildOp.getCardinality();
        for (size_t i = 0; i < joinConditions.size(); ++i) {
            estCardinality *= PlannerKnobs::EQUALITY_PREDICATE_SELECTIVITY;
        }
        return atLeastOne(estCardinality);
    }
}

uint64_t CardinalityEstimator::estimateCrossProduct(const LogicalOperator& probeOp,
    const LogicalOperator& buildOp) const {
    return atLeastOne(probeOp.getCardinality() * buildOp.getCardinality());
}

uint64_t CardinalityEstimator::estimateIntersect(const expression_vector& joinNodeIDs,
    const LogicalOperator& probeOp, const std::vector<LogicalOperator*>& buildOps) const {
    // Formula 1: treat intersect as a Filter on probe side.
    uint64_t estCardinality1 =
        probeOp.getCardinality() * PlannerKnobs::NON_EQUALITY_PREDICATE_SELECTIVITY;
    // Formula 2: assume independence on join conditions.
    cardinality_t denominator = 1u;
    for (auto& joinNodeID : joinNodeIDs) {
        denominator *= getNodeIDDom(joinNodeID->getUniqueName());
    }
    auto numerator = probeOp.getCardinality();
    for (auto& buildOp : buildOps) {
        numerator *= buildOp->getCardinality();
    }
    auto estCardinality2 = numerator / atLeastOne(denominator);
    // Pick minimum between the two formulas.
    return atLeastOne(std::min<uint64_t>(estCardinality1, estCardinality2));
}

uint64_t CardinalityEstimator::estimateFlatten(const LogicalOperator& childOp,
    f_group_pos groupPosToFlatten) const {
    auto group = childOp.getSchema()->getGroup(groupPosToFlatten);
    return atLeastOne(childOp.getCardinality() * group->cardinalityMultiplier);
}

static bool isPrimaryKey(const Expression& expression) {
    if (expression.expressionType != ExpressionType::PROPERTY) {
        return false;
    }
    return ((PropertyExpression&)expression).isPrimaryKey();
}

static bool isSingleLabelledProperty(const Expression& expression) {
    if (expression.expressionType != ExpressionType::PROPERTY) {
        return false;
    }
    return expression.constCast<PropertyExpression>().isSingleLabel();
}

static std::optional<cardinality_t> getTableStatsIfPossible(main::ClientContext* context,
    const Expression& predicate,
    const std::unordered_map<common::table_id_t, storage::TableStats>& nodeTableStats) {
    DASSERT(predicate.getNumChildren() >= 1);
    if (isSingleLabelledProperty(*predicate.getChild(0))) {
        auto& propertyExpr = predicate.getChild(0)->cast<PropertyExpression>();
        auto tableID = propertyExpr.getSingleTableID();
        if (nodeTableStats.contains(tableID) && propertyExpr.hasProperty(tableID)) {
            auto transaction = Transaction::Get(*context);
            auto entry =
                catalog::Catalog::Get(*context)->getTableCatalogEntry(transaction, tableID);
            auto columnID = entry->getColumnID(propertyExpr.getPropertyName());
            if (columnID != INVALID_COLUMN_ID && columnID != ROW_IDX_COLUMN_ID) {
                auto& stats = nodeTableStats.at(tableID);
                return atLeastOne(stats.getNumDistinctValues(columnID));
            }
        }
    }
    return {};
}

uint64_t CardinalityEstimator::estimateFilter(const LogicalOperator& childPlan,
    const Expression& predicate) const {
    if (predicate.expressionType == ExpressionType::EQUALS) {
        if (isPrimaryKey(*predicate.getChild(0)) || isPrimaryKey(*predicate.getChild(1))) {
            return 1;
        } else {
            const auto numDistinctValues =
                getTableStatsIfPossible(context, predicate, nodeTableStats);
            if (numDistinctValues.has_value()) {
                return atLeastOne(childPlan.getCardinality() / numDistinctValues.value());
            }
            return atLeastOne(
                childPlan.getCardinality() * PlannerKnobs::EQUALITY_PREDICATE_SELECTIVITY);
        }
    } else {
        return atLeastOne(
            childPlan.getCardinality() * PlannerKnobs::NON_EQUALITY_PREDICATE_SELECTIVITY);
    }
}

uint64_t CardinalityEstimator::getNumNodes(const Transaction*,
    const std::vector<table_id_t>& tableIDs) const {
    cardinality_t numNodes = 0u;
    for (auto& tableID : tableIDs) {
        // Skip foreign tables - they won't be in nodeTableStats
        if (!nodeTableStats.contains(tableID)) {
            continue;
        }
        numNodes += nodeTableStats.at(tableID).getTableCard();
    }
    return atLeastOne(numNodes);
}

uint64_t CardinalityEstimator::getNumRels(const Transaction* transaction,
    const std::vector<table_id_t>& tableIDs) const {
    cardinality_t numRels = 0u;
    for (auto tableID : tableIDs) {
        numRels +=
            storage::StorageManager::Get(*context)->getTable(tableID)->getNumTotalRows(transaction);
    }
    return atLeastOne(numRels);
}

double CardinalityEstimator::getExtensionRate(const RelExpression& rel,
    const NodeExpression& boundNode, const Transaction* transaction) const {
    auto numBoundNodes = static_cast<double>(getNumNodes(transaction, boundNode.getTableIDs()));
    auto numRels = static_cast<double>(getNumRels(transaction, rel.getInnerRelTableIDs()));
    DASSERT(numBoundNodes > 0);
    auto oneHopExtensionRate = numRels / atLeastOne(numBoundNodes);
    switch (rel.getRelType()) {
    case QueryRelType::NON_RECURSIVE: {
        return oneHopExtensionRate;
    }
    case QueryRelType::VARIABLE_LENGTH_WALK:
    case QueryRelType::VARIABLE_LENGTH_TRAIL:
    case QueryRelType::VARIABLE_LENGTH_ACYCLIC: {
        auto rate = oneHopExtensionRate *
                    std::max<uint16_t>(rel.getRecursiveInfo()->bindData->upperBound, 1);
        return rate * context->getClientConfig()->recursivePatternCardinalityScaleFactor;
    }
    case QueryRelType::SHORTEST:
    case QueryRelType::ALL_SHORTEST:
    case QueryRelType::WEIGHTED_SHORTEST:
    case QueryRelType::ALL_WEIGHTED_SHORTEST: {
        auto rate = std::min<double>(
            oneHopExtensionRate *
                std::max<uint16_t>(rel.getRecursiveInfo()->bindData->upperBound, 1),
            numRels);
        return rate * context->getClientConfig()->recursivePatternCardinalityScaleFactor;
    }
    default:
        UNREACHABLE_CODE;
    }
}

} // namespace planner
} // namespace lbug