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Unit tests for SQLite row counters.
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There's a couple of oddities noted in there that need further
explanation, but the counters seem mostly reasonable.
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@smerritt
smerritt committed Aug 4, 2023
1 parent 409bf45 commit 217fadf
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261 changes: 261 additions & 0 deletions src/workerd/util/sqlite-test.c++
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// https://opensource.org/licenses/Apache-2.0

#include "sqlite.h"
#include <cstdint>
#include <kj/test.h>
#include <kj/thread.h>
#include <stdlib.h>
Expand Down Expand Up @@ -366,5 +367,265 @@ KJ_TEST("SQLite onWrite callback") {
KJ_EXPECT(sawWrite);
}

struct RowCounts {
int64_t found;
int64_t read;
int64_t written;
};

template<typename ...Params>
RowCounts countRowsTouched(SqliteDatabase& db, SqliteDatabase::Regulator& regulator, kj::StringPtr sqlCode, Params... bindParams) {
int64_t readBefore = db.getRowsRead();
int64_t writtenBefore = db.getRowsWritten();
int64_t rowsFound = 0;

// Runs a query; retrieves and discards all the data.
auto query = db.run(regulator, sqlCode, bindParams...);
while (!query.isDone()) {
rowsFound++;
query.nextRow();
}

return {.found = rowsFound,
.read = db.getRowsRead() - readBefore,
.written = db.getRowsWritten() - writtenBefore};
}

template<typename ...Params>
RowCounts countRowsTouched(SqliteDatabase& db, kj::StringPtr sqlCode, Params... bindParams) {
return countRowsTouched(db, SqliteDatabase::TRUSTED, sqlCode, std::forward<Params>(bindParams)...);
}

KJ_TEST("SQLite read row counters (basic)") {
auto dir = kj::newInMemoryDirectory(kj::nullClock());
SqliteDatabase::Vfs vfs(*dir);
SqliteDatabase db(vfs, kj::Path({"foo"}), kj::WriteMode::CREATE | kj::WriteMode::MODIFY);

db.run(R"(
CREATE TABLE things (
id INTEGER PRIMARY KEY,
unindexed_int INTEGER,
value TEXT
);
)");

constexpr int dbRowCount = 1000;
auto insertStmt = db.prepare("INSERT INTO things (id, unindexed_int, value) VALUES (?, ?, ?)");
for (int i = 0; i < dbRowCount; i++) {
insertStmt.run(i, i * 1000, kj::str("value", i));
}

// Sanity check that the inserts worked.
{
auto getCount = db.prepare("SELECT COUNT(*) FROM things");
KJ_EXPECT(getCount.run().getInt(0) == dbRowCount);
}

// Selecting all the rows reads all the rows.
{
RowCounts stats = countRowsTouched(db, "SELECT * FROM things");
KJ_EXPECT(stats.found == dbRowCount);
KJ_EXPECT(stats.read == dbRowCount);
KJ_EXPECT(stats.written == 0);
}

// Selecting one row using an index reads one row.
{
RowCounts stats = countRowsTouched(db,"SELECT * FROM things WHERE id=?", 5);
KJ_EXPECT(stats.found == 1);
KJ_EXPECT(stats.read == 1);
KJ_EXPECT(stats.written == 0);
}

// Selecting one row using an reads one row, even if that row is in the middle of the table.
{
RowCounts stats = countRowsTouched(db,"SELECT * FROM things WHERE id=?", dbRowCount / 2);
KJ_EXPECT(stats.found == 1);
KJ_EXPECT(stats.read == 1);
KJ_EXPECT(stats.written == 0);
}

// Selecting a row by an unindexed value reads the whole table.
{
RowCounts stats = countRowsTouched(db, "SELECT * FROM things WHERE unindexed_int = ?", 5000);
KJ_EXPECT(stats.found == 1);
KJ_EXPECT(stats.read == dbRowCount);
KJ_EXPECT(stats.written == 0);
}

// Selecting two rows with an IN clause reads four rows and writes two, apparently. XXX why?
{
RowCounts stats = countRowsTouched(db, "SELECT * FROM things WHERE id IN (2, 3)");
KJ_EXPECT(stats.read == 4);
KJ_EXPECT(stats.written == 2);
}

// Selecting an unindexed aggregate scans all the rows, which counts as reading them.
{
RowCounts stats = countRowsTouched(db, "SELECT MAX(unindexed_int) FROM things");
KJ_EXPECT(stats.found == 1);
KJ_EXPECT(stats.read == dbRowCount);
KJ_EXPECT(stats.written == 0);
}

// Selecting an indexed aggregate can use the index, so it only reads the row it found.
{
RowCounts stats = countRowsTouched(db, "SELECT MIN(id) FROM things");
KJ_EXPECT(stats.found == 1);
KJ_EXPECT(stats.read == 1);
KJ_EXPECT(stats.written == 0);
}

// Selecting with a limit only reads the returned rows.
{
RowCounts stats = countRowsTouched(db, "SELECT * FROM things LIMIT 5");
KJ_EXPECT(stats.found == 5);
KJ_EXPECT(stats.read == 5);
KJ_EXPECT(stats.written == 0);

}
}

KJ_TEST("SQLite write row counters (basic)") {
auto dir = kj::newInMemoryDirectory(kj::nullClock());
SqliteDatabase::Vfs vfs(*dir);
SqliteDatabase db(vfs, kj::Path({"foo"}), kj::WriteMode::CREATE | kj::WriteMode::MODIFY);

db.run(R"(
CREATE TABLE things (
id INTEGER PRIMARY KEY
);
)");

db.run(R"(
CREATE TABLE unindexed_things (
id INTEGER
);
)");

// Inserting a row counts as one row written.
{
RowCounts stats = countRowsTouched(db, "INSERT INTO unindexed_things (id) VALUES (?)", 1);
KJ_EXPECT(stats.read == 0);
KJ_EXPECT(stats.written == 1);
}

// Inserting a row into a table with a primary key will also do a read (to ensure there's no
// duplicate PK).
{
RowCounts stats = countRowsTouched(db, "INSERT INTO things (id) VALUES (?)", 1);
KJ_EXPECT(stats.read == 1);
KJ_EXPECT(stats.written == 1);
}

// Deleting a row counts as a write.
{
RowCounts stats = countRowsTouched(db, "INSERT INTO things (id) VALUES (?)", 123);
KJ_EXPECT(stats.written == 1);

stats = countRowsTouched(db, "DELETE FROM things WHERE id=?", 123);
KJ_EXPECT(stats.read == 1);
KJ_EXPECT(stats.written == 1);
}

// Deleting nothing is not a write.
{
RowCounts stats = countRowsTouched(db, "DELETE FROM things WHERE id=?", 998877112233);
KJ_EXPECT(stats.written == 0);
}

// Inserting many things is many writes.
{
db.run("DELETE FROM things");
db.run("INSERT INTO things (id) VALUES (1)");
db.run("INSERT INTO things (id) VALUES (3)");
db.run("INSERT INTO things (id) VALUES (5)");

RowCounts stats = countRowsTouched(db, "INSERT INTO unindexed_things (id) SELECT id FROM things");
KJ_EXPECT(stats.read == 3);
KJ_EXPECT(stats.written == 3);
}

// Each updated row is a write.
{
db.run("DELETE FROM unindexed_things");
db.run("INSERT INTO unindexed_things (id) VALUES (1)");
db.run("INSERT INTO unindexed_things (id) VALUES (2)");
db.run("INSERT INTO unindexed_things (id) VALUES (3)");
db.run("INSERT INTO unindexed_things (id) VALUES (4)");

RowCounts stats = countRowsTouched(db, "UPDATE unindexed_things SET id = id * 10 WHERE id >= 3");
KJ_EXPECT(stats.written == 2);
}

// On an indexed table, each updated row is two writes. XXX why?
{
db.run("DELETE FROM things");
db.run("INSERT INTO things (id) VALUES (1)");
db.run("INSERT INTO things (id) VALUES (2)");
db.run("INSERT INTO things (id) VALUES (3)");
db.run("INSERT INTO things (id) VALUES (4)");

RowCounts stats = countRowsTouched(db, "UPDATE things SET id = id * 10 WHERE id >= 3");
KJ_EXPECT(stats.written == 4);
}
}

KJ_TEST("SQLite row counters with triggers") {
auto dir = kj::newInMemoryDirectory(kj::nullClock());
SqliteDatabase::Vfs vfs(*dir);
SqliteDatabase db(vfs, kj::Path({"foo"}), kj::WriteMode::CREATE | kj::WriteMode::MODIFY);

class RegulatorImpl: public SqliteDatabase::Regulator {
public:
RegulatorImpl() = default;

bool isAllowedTrigger(kj::StringPtr name) override {
// SqliteDatabase::TRUSTED doesn't let us use triggers at all.
return true;
}
};

RegulatorImpl regulator;

db.run(R"(
CREATE TABLE things (
id INTEGER PRIMARY KEY
);
CREATE TABLE log (
id INTEGER,
verb TEXT
);
CREATE TRIGGER log_inserts AFTER INSERT ON things
BEGIN
insert into log (id, verb) VALUES (NEW.id, "INSERT");
END;
CREATE TRIGGER log_deletes AFTER DELETE ON things
BEGIN
insert into log (id, verb) VALUES (OLD.id, "DELETE");
END;
)");

// Each insert counts as two writes: one for the row in `things` and one for the row in `log`.
{
RowCounts stats = countRowsTouched(db, regulator, "INSERT INTO things (id) VALUES (1)");
KJ_EXPECT(stats.written == 2);
}

// A deletion counts as two writes: one for the row and one for the log.
{
db.run(regulator, "DELETE FROM things");
db.run(regulator, "INSERT INTO things (id) VALUES (1)");
db.run(regulator, "INSERT INTO things (id) VALUES (2)");
db.run(regulator, "INSERT INTO things (id) VALUES (3)");

RowCounts stats = countRowsTouched(db, regulator, "DELETE FROM things");
KJ_EXPECT(stats.written == 6);
}
}

} // namespace
} // namespace workerd

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