matchPrefix

matchPrefix(textCol, prefix, [scoreColName])

textCol 待查询的列，即 PKEY 存储引擎中设置了文本索引的列。

prefix STRING 类型标量，用于指定待查询的前缀。

scoreColName 可选参数，STRING 类型标量，表示输出结果中文本匹配得分列的列名。默认值为空，此时不输出得分列。匹配得分代表数据在分区内的匹配程度，不同分区的分数不可比较。

该函数用于 SQL 语句的 WHERE 子句，针对 PKEY 存储引擎中设置文本索引的列进行前缀匹配，返回包含指定前缀的行。

// 构造数据
stringColumn = ["There are some apples and oranges.","Mike likes apples.","Alice likes oranges.","Mike gives Alice an apple.","Alice gives Mike an orange.","John likes peaches, so he does not give them to anyone.","Mike, can you give me some apples?","Alice, can you give me some oranges?","Mike traded an orange for an apple with Alice."]
t = table([1,1,1,2,2,2,3,3,3] as id1, [1,2,3,1,2,3,1,2,3] as id2, stringColumn as remark) 
if(existsDatabase("dfs://textDB")) dropDatabase("dfs://textDB")
db = database(directory="dfs://textDB", partitionType=VALUE, partitionScheme=[1,2,3], engine="PKEY")
pt = createPartitionedTable(dbHandle=db, table=t, tableName="pt", partitionColumns="id1",primaryKey=`id1`id2,indexes={"remark":"textindex(parser=english, full=false, lowercase=true, stem=true)"})
pt.tableInsert(t)

// 匹配包含前缀是 app 的单词的行
select * from pt where matchPrefix(remark,"app")