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sqlite: Observer database changes through WAL hook
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -94,4 +94,5 @@ Api::_setup_db() { | |
| for (const auto& cmd : setup_commands) { | ||
| m_sqlite->exec(cmd); | ||
| } | ||
| m_sqlite->enable_wal(); | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,5 +1,4 @@ | ||
| #include "query_diff.hpp" | ||
| #include <algorithm> | ||
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| namespace mx3 { namespace sqlite { | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| #include "query_monitor.hpp" | ||
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| namespace mx3 { | ||
| namespace sqlite { | ||
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| class QueryMonitor::only_for_internal_use_by_make_shared_t {}; | ||
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| shared_ptr<QueryMonitor> QueryMonitor::create_shared(const shared_ptr<Db> & write_db) { | ||
| return make_shared<QueryMonitor>(only_for_internal_use_by_make_shared_t{}, write_db); | ||
| } | ||
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| QueryMonitor::QueryMonitor( | ||
| only_for_internal_use_by_make_shared_t, | ||
| const shared_ptr<Db> & write_db) : m_write_db(write_db) | ||
| { | ||
| _install_hooks(); | ||
| } | ||
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| QueryMonitor::~QueryMonitor() { | ||
| m_write_db->update_hook(nullptr); | ||
| m_write_db->commit_hook(nullptr); | ||
| m_write_db->rollback_hook(nullptr); | ||
| m_write_db->wal_hook(nullptr); | ||
| } | ||
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| void QueryMonitor::listen_to_changes(const function<void()> & fn) { | ||
| m_listeners.push_back(fn); | ||
| } | ||
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| void QueryMonitor::_install_hooks() { | ||
| m_write_db->update_hook([this] (Db::Change change) { | ||
| this->_on_update(std::move(change)); | ||
| }); | ||
| m_write_db->commit_hook([this] () { | ||
| return this->_on_commit(); | ||
| }); | ||
| m_write_db->rollback_hook([this] () { | ||
| this->_on_rollback(); | ||
| }); | ||
| m_write_db->wal_hook([this] (const string& db_name, int pages) { | ||
| this->_on_wal_commit(db_name, pages); | ||
| }); | ||
| } | ||
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| void QueryMonitor::_on_update(Db::Change) {} | ||
| bool QueryMonitor::_on_commit() { | ||
| return true; | ||
| } | ||
| void QueryMonitor::_on_rollback() {} | ||
| bool QueryMonitor::_on_wal_commit(const string& db_name, int pages) { | ||
| if (pages > 1000) { | ||
| m_write_db->wal_checkpoint_v2(db_name, Checkpoint::PASSIVE); | ||
| } | ||
| // Grab size before iterating in case m_listeners is modified in a callback. | ||
| // In actuality this should be posted to an event loop, but oh well - its only a demo app | ||
| const size_t total = m_listeners.size(); | ||
| for (size_t i=0; i < total; i++) { | ||
| m_listeners[i](); | ||
| } | ||
| return true; | ||
| } | ||
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| } } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| #pragma once | ||
| #include "../sqlite/sqlite.hpp" | ||
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| namespace mx3 { | ||
| namespace sqlite { | ||
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| /* This class listens to changes in WAL mode databases. | ||
| * And will notify listeners when changes are made. | ||
| */ | ||
| class QueryMonitor final { | ||
| public: | ||
| static shared_ptr<QueryMonitor> create_shared(const shared_ptr<Db> & write_db); | ||
| ~QueryMonitor(); | ||
| void listen_to_changes(const function<void()> & fn); | ||
| private: | ||
| class only_for_internal_use_by_make_shared_t; | ||
| public: | ||
| // make_shared constructor | ||
| QueryMonitor(only_for_internal_use_by_make_shared_t flag, const shared_ptr<Db> & write_db); | ||
| private: | ||
| void _install_hooks(); | ||
| void _on_update(Db::Change); | ||
| bool _on_commit(); | ||
| void _on_rollback(); | ||
| bool _on_wal_commit(const string& db_name, int pages); | ||
| const shared_ptr<Db> m_write_db; | ||
| vector<function<void()>> m_listeners; | ||
| }; | ||
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| } } |
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