聊聊claudb的list command
序
本文主要研究一下claudb的list command
LeftPushCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/LeftPushCommand.java
@Command("lpush")
@ParamLength(2)
@ParamType(DataType.LIST)
public class LeftPushCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
ImmutableList<SafeString> values = request.getParams().asList().tail().reverse();
DatabaseValue result = db.merge(safeKey(request.getParam(0)), list(values),
(oldValue, newValue) -> list(newValue.getList().appendAll(oldValue.getList())));
return RedisToken.integer(result.size());
}
}
- LeftPushCommand实现了DBCommand接口,其execute方法提取values,然后执行db.merge,在newValue.getList()之后追加上oldValue.getList()
LeftPopCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/LeftPopCommand.java
@Command("lpop")
@ParamLength(1)
@ParamType(DataType.LIST)
public class LeftPopCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
List<SafeString> removed = new LinkedList<>();
db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,
(oldValue, newValue) -> {
ImmutableList<SafeString> list = oldValue.getList();
list.head().stream().forEach(removed::add);
return list(list.tail());
});
if (removed.isEmpty()) {
return nullString();
} else {
return string(removed.remove(0));
}
}
}
- LeftPopCommand实现了DBCommand接口,其execute方法执行db.merge,它先获取oldValue.getList(),然后取出head添加到removed中,然后再通过list.tail()丢弃head作为新的结果
RightPushCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/RightPushCommand.java
@Command("rpush")
@ParamLength(2)
@ParamType(DataType.LIST)
public class RightPushCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
ImmutableList<SafeString> values = request.getParams().asList().tail();
DatabaseValue result = db.merge(safeKey(request.getParam(0)), list(values),
(oldValue, newValue) -> list(oldValue.getList().appendAll(newValue.getList())));
return integer(result.size());
}
}
- RightPushCommand实现了DBCommand接口,其execute方法提取values,然后执行db.merge,在oldValue.getList()之后追加上newValue.getList()
RightPopCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/RightPopCommand.java
@Command("rpop")
@ParamLength(1)
@ParamType(DataType.LIST)
public class RightPopCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
List<SafeString> removed = new LinkedList<>();
db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,
(oldValue, newValue) -> {
ImmutableList<SafeString> list = oldValue.getList();
list.reverse().head().stream().forEach(removed::add);
return list(list.reverse().tail().reverse());
});
if (removed.isEmpty()) {
return nullString();
} else {
return string(removed.remove(0));
}
}
}
- RightPopCommand实现了DBCommand接口,其execute方法执行db.merge,它先获取oldValue.getList(),然后取出list倒数的head添加到removed中,然后再通过list.reverse().tail()丢弃head再reverse作为新的结果
ListLengthCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListLengthCommand.java
@ReadOnly
@Command("llen")
@ParamLength(1)
@ParamType(DataType.LIST)
public class ListLengthCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
ImmutableList<SafeString> list = db.getList(request.getParam(0));
return integer(list.size());
}
}
- ListLengthCommand实现了DBCommand接口,其execute方法先通过db.getList(request.getParam(0))获取list,然后返回integer(list.size())
ListRangeCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListRangeCommand.java
@ReadOnly
@Command("lrange")
@ParamLength(3)
@ParamType(DataType.LIST)
public class ListRangeCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
try {
DatabaseValue value = db.getOrDefault(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST);
ImmutableList<SafeString> list = value.getList();
int from = Integer.parseInt(request.getParam(1).toString());
if (from < 0) {
from = list.size() + from;
}
int to = Integer.parseInt(request.getParam(2).toString());
if (to < 0) {
to = list.size() + to;
}
int min = Math.min(from, to);
int max = Math.max(from, to);
// TODO: use Array
ImmutableList<SafeString> result = ImmutableList.from(list.stream().skip(min).limit((max - min) + 1));
return convert(result);
} catch (NumberFormatException e) {
return error("ERR value is not an integer or out of range");
}
}
}
- ListRangeCommand实现了DBCommand接口,其execute方法先获取list,之后修正min及max,然后取ImmutableList.from(list.stream().skip(min).limit((max - min) + 1))
ListIndexCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListIndexCommand.java
@ReadOnly
@Command("lindex")
@ParamLength(2)
@ParamType(DataType.LIST)
public class ListIndexCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
try {
ImmutableList<SafeString> list = db.getList(request.getParam(0));
int index = Integer.parseInt(request.getParam(1).toString());
if (index < 0) {
index = list.size() + index;
}
// TODO: fix asArray
return string(list.asArray().get(index));
} catch (NumberFormatException e) {
return error("ERR value is not an integer or out of range");
} catch (IndexOutOfBoundsException e) {
return nullString();
}
}
}
- ListIndexCommand实现了DBCommand接口,其execute方法先获取list,然后返回string(list.asArray().get(index))
ListSetCommand
claudb-1.7.1/src/main/java/com/github/tonivade/claudb/command/list/ListSetCommand.java
@Command("lset")
@ParamLength(3)
@ParamType(DataType.LIST)
public class ListSetCommand implements DBCommand {
@Override
public RedisToken execute(Database db, Request request) {
try {
int index = Integer.parseInt(request.getParam(1).toString());
db.merge(safeKey(request.getParam(0)), DatabaseValue.EMPTY_LIST,
(oldValue, newValue) -> {
ImmutableList<SafeString> oldList = oldValue.getList();
// TODO: use Array
List<SafeString> array = new ArrayList<>(oldList.toList());
array.set(index > -1 ? index : array.size() + index, request.getParam(2));
return list(array);
});
return status("OK");
} catch (NumberFormatException e) {
return error("ERR value is not an integer or out of range");
} catch (IndexOutOfBoundsException e) {
return error("ERR index out of range");
}
}
}
- ListSetCommand实现了DBCommand接口,其execute方法先读取index参数,然后执行db.merge,它读取oldList,然后执行array.set(index > -1 ? index : array.size() + index, request.getParam(2)),最后返回list(array)
小结
claudb list相关的command有LeftPushCommand、LeftPopCommand、RightPushCommand、RightPopCommand、ListLengthCommand、ListRangeCommand、ListIndexCommand、ListSetCommand
doc
- command/list
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