diff --git a/CHANGELOG.md b/CHANGELOG.md
index e26675074..4ea2b5e76 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
* Map indexing supported.
* `assert` function added.
* Use \u to specify 4 digit codepoint and \U for 8 digit
+* `counter` function added.
### Bug Fixes and Other Changes
diff --git a/docs/user_technical/open-cypher.md b/docs/user_technical/open-cypher.md
index 010024c0b..acafd3a23 100644
--- a/docs/user_technical/open-cypher.md
+++ b/docs/user_technical/open-cypher.md
@@ -500,6 +500,7 @@ functions.
`contains` | Check if the first argument has an element which is equal to the second argument.
`all` | Check if all elements of a list satisfy a predicate.<br/>The syntax is: `all(variable IN list WHERE predicate)`.
`assert` | Raises an exception reported to the client if the given argument is not `true`.
+ `counter` | Generates integers that are guaranteed to be unique on the database level, for the given counter name.
#### String Operators
diff --git a/src/database/graph_db.hpp b/src/database/graph_db.hpp
index 6e2e8452f..a118c1707 100644
--- a/src/database/graph_db.hpp
+++ b/src/database/graph_db.hpp
@@ -5,6 +5,7 @@
#include "cppitertools/filter.hpp"
#include "cppitertools/imap.hpp"
+#include "data_structures/concurrent/concurrent_map.hpp"
#include "data_structures/concurrent/concurrent_set.hpp"
#include "data_structures/concurrent/skiplist.hpp"
#include "database/graph_db_datatypes.hpp"
@@ -120,4 +121,7 @@ class GraphDb {
// Periodically wakes up and hints to transactions that are running for a long
// time to stop their execution.
Scheduler transaction_killer_;
+
+ // DB level global counters, used in the "counter" function
+ ConcurrentMap<std::string, std::atomic<int64_t>> counters_;
};
diff --git a/src/database/graph_db_accessor.cpp b/src/database/graph_db_accessor.cpp
index ac7d3b668..0064de484 100644
--- a/src/database/graph_db_accessor.cpp
+++ b/src/database/graph_db_accessor.cpp
@@ -328,3 +328,9 @@ const std::string &GraphDbAccessor::PropertyName(
debug_assert(!commited_ && !aborted_, "Accessor committed or aborted");
return *property;
}
+
+int64_t GraphDbAccessor::Counter(const std::string &name) {
+ return db_.counters_.access()
+ .emplace(name, std::make_tuple(name), std::make_tuple(0))
+ .first->second.fetch_add(1);
+}
diff --git a/src/database/graph_db_accessor.hpp b/src/database/graph_db_accessor.hpp
index 0e32b5e44..8c27cee36 100644
--- a/src/database/graph_db_accessor.hpp
+++ b/src/database/graph_db_accessor.hpp
@@ -561,6 +561,13 @@ class GraphDbAccessor {
if (!accessor.new_) accessor.new_ = accessor.vlist_->update(*transaction_);
}
+ /**
+ * Returns the current value of the counter with the given name, and
+ * increments that counter. If the counter with the given name does not exist,
+ * a new counter is created and this function returns 0.
+ */
+ int64_t Counter(const std::string &name);
+
private:
/**
* Insert this vertex into corresponding label and label+property (if it
diff --git a/src/query/interpret/awesome_memgraph_functions.cpp b/src/query/interpret/awesome_memgraph_functions.cpp
index 8c1bc0b20..0c773eaf5 100644
--- a/src/query/interpret/awesome_memgraph_functions.cpp
+++ b/src/query/interpret/awesome_memgraph_functions.cpp
@@ -512,18 +512,27 @@ TypedValue Assert(const std::vector<TypedValue> &args, GraphDbAccessor &) {
throw QueryRuntimeException("assert takes one or two arguments");
}
if (args[0].type() != TypedValue::Type::Bool)
- throw QueryRuntimeException("first assert argument must be bool");
+ throw QueryRuntimeException("first assert argument must be bool");
if (args.size() == 2U && args[1].type() != TypedValue::Type::String)
- throw QueryRuntimeException("second assert argument must be a string");
+ throw QueryRuntimeException("second assert argument must be a string");
if (!args[0].ValueBool()) {
std::string message("assertion failed");
- if (args.size() == 2U)
- message += ": " + args[1].ValueString();
+ if (args.size() == 2U) message += ": " + args[1].ValueString();
throw QueryRuntimeException(message);
}
return args[0];
}
-} // annonymous namespace
+
+TypedValue Counter(const std::vector<TypedValue> &args, GraphDbAccessor &dba) {
+ if (args.size() != 1U) {
+ throw QueryRuntimeException("counter takes one argument");
+ }
+ if (!args[0].IsString())
+ throw QueryRuntimeException("first counter argument must be a string");
+
+ return dba.Counter(args[0].ValueString());
+}
+} // annonymous namespace
std::function<TypedValue(const std::vector<TypedValue> &, GraphDbAccessor &)>
NameToFunction(const std::string &function_name) {
@@ -566,6 +575,7 @@ NameToFunction(const std::string &function_name) {
if (function_name == kEndsWith) return EndsWith;
if (function_name == kContains) return Contains;
if (function_name == "ASSERT") return Assert;
+ if (function_name == "COUNTER") return Counter;
return nullptr;
}
-} // namespace query
+} // namespace query
diff --git a/tests/qa/tck_engine/tests/memgraph_V1/features/functions.feature b/tests/qa/tck_engine/tests/memgraph_V1/features/functions.feature
index 8025500cf..7e252b3f3 100644
--- a/tests/qa/tck_engine/tests/memgraph_V1/features/functions.feature
+++ b/tests/qa/tck_engine/tests/memgraph_V1/features/functions.feature
@@ -690,3 +690,20 @@ Feature: Functions
Then the result should be:
| res |
| true |
+
+ Scenario: Counter test:
+ Given an empty graph
+ And having executed:
+ """
+ CREATE (), (), ()
+ """
+ When executing query:
+ """
+ MATCH (n) SET n.id = counter("n.id") WITH n SKIP 1
+ RETURN n.id, counter("other") AS c2
+ """
+ Then the result should be:
+ | n.id | c2 |
+ | 1 | 0 |
+ | 2 | 1 |
+
diff --git a/tests/unit/query_expression_evaluator.cpp b/tests/unit/query_expression_evaluator.cpp
index 44afc4fde..4d350736c 100644
--- a/tests/unit/query_expression_evaluator.cpp
+++ b/tests/unit/query_expression_evaluator.cpp
@@ -36,11 +36,13 @@ struct NoContextExpressionEvaluator {
};
TypedValue EvaluateFunction(const std::string &function_name,
- const std::vector<TypedValue> &args) {
+ const std::vector<TypedValue> &args, Dbms &dbms) {
AstTreeStorage storage;
- NoContextExpressionEvaluator eval;
- Dbms dbms;
+ SymbolTable symbol_table;
auto dba = dbms.active();
+ Frame frame{128};
+ Parameters parameters;
+ ExpressionEvaluator eval{frame, parameters, symbol_table, *dba};
std::vector<Expression *> expressions;
for (const auto &arg : args) {
@@ -48,7 +50,13 @@ TypedValue EvaluateFunction(const std::string &function_name,
}
auto *op =
storage.Create<Function>(NameToFunction(function_name), expressions);
- return op->Accept(eval.eval);
+ return op->Accept(eval);
+}
+
+TypedValue EvaluateFunction(const std::string &function_name,
+ const std::vector<TypedValue> &args) {
+ Dbms dbms;
+ return EvaluateFunction(function_name, args, dbms);
}
TEST(ExpressionEvaluator, OrOperator) {
@@ -1166,13 +1174,17 @@ TEST(ExpressionEvaluator, FunctionAllWhereWrongType) {
TEST(ExpressionEvaluator, FunctionAssert) {
// Invalid calls.
ASSERT_THROW(EvaluateFunction("ASSERT", {}), QueryRuntimeException);
- ASSERT_THROW(EvaluateFunction("ASSERT", {false, false}), QueryRuntimeException);
- ASSERT_THROW(EvaluateFunction("ASSERT", {"string", false}), QueryRuntimeException);
- ASSERT_THROW(EvaluateFunction("ASSERT", {false, "reason", true}), QueryRuntimeException);
+ ASSERT_THROW(EvaluateFunction("ASSERT", {false, false}),
+ QueryRuntimeException);
+ ASSERT_THROW(EvaluateFunction("ASSERT", {"string", false}),
+ QueryRuntimeException);
+ ASSERT_THROW(EvaluateFunction("ASSERT", {false, "reason", true}),
+ QueryRuntimeException);
// Valid calls, assertion fails.
ASSERT_THROW(EvaluateFunction("ASSERT", {false}), QueryRuntimeException);
- ASSERT_THROW(EvaluateFunction("ASSERT", {false, "message"}), QueryRuntimeException);
+ ASSERT_THROW(EvaluateFunction("ASSERT", {false, "message"}),
+ QueryRuntimeException);
try {
EvaluateFunction("ASSERT", {false, "bbgba"});
} catch (QueryRuntimeException &e) {
@@ -1194,4 +1206,16 @@ TEST(ExpressionEvaluator, ParameterLookup) {
EXPECT_EQ(value.Value<int64_t>(), 42);
}
+TEST(ExpressionEvaluator, FunctionCounter) {
+ Dbms dbms;
+ EXPECT_THROW(EvaluateFunction("COUNTER", {}, dbms), QueryRuntimeException);
+ EXPECT_THROW(EvaluateFunction("COUNTER", {"a", "b"}, dbms),
+ QueryRuntimeException);
+ EXPECT_EQ(EvaluateFunction("COUNTER", {"c1"}, dbms).ValueInt(), 0);
+ EXPECT_EQ(EvaluateFunction("COUNTER", {"c1"}, dbms).ValueInt(), 1);
+ EXPECT_EQ(EvaluateFunction("COUNTER", {"c2"}, dbms).ValueInt(), 0);
+ EXPECT_EQ(EvaluateFunction("COUNTER", {"c1"}, dbms).ValueInt(), 2);
+ EXPECT_EQ(EvaluateFunction("COUNTER", {"c2"}, dbms).ValueInt(), 1);
+}
+
} // namespace