更新：我修改了在无类型（所有字符串类型列）表中推断数据类型的 SP，它现在直接针对 Snowflake 阶段工作。项目代码在这里：https://github.com/GregPavlik/InferSchema
我写了一个存储过程来帮助解决这个问题；但是，它的唯一目标是推断无类型列的数据类型。它的工作原理如下：
- 将 CSV 加载到表中，所有列都定义为 varchars。
- 通过对新表的查询调用 SP（要点是只获取您想要的列并限制行数以保持合理的类型推断时间）。
- SP 调用中还包含旧位置和新位置的数据库、架构和表 - old 带有所有 varchar，new 带有推断类型。
然后，SP 将推断数据类型并创建两个 SQL 语句。一条语句将使用推断的数据类型创建新表。一条语句将使用适当的包装器（例如 try_multi_timestamp()，一个扩展 try_to_timestamp() 以尝试各种常见格式的 UDF）从无类型（所有 varchar）表复制到新表。
我打算扩展它，使它根本不需要无类型（全 varchar）表，但还没有解决它。既然它出现在这里，我可能会回过头来用这种能力更新 SP。您可以指定直接从阶段读取的查询，但您必须使用 $1、$2... 和列名的别名（否则 DDL 将尝试创建像 $1 这样的列名）。如果查询直接针对某个阶段运行，对于旧的数据库、模式和表，您可以放入任何内容，因为这仅用于从 select 语句生成插入。
-- This shows how to use on the Snowflake TPCH sample, but could be any query.
-- Keep the row count down to reduce the time it take to infer the types.
call infer_data_types('select * from SNOWFLAKE_SAMPLE_DATA.TPCH_SF1.LINEITEM limit 10000',
'SNOWFLAKE_SAMPLE_DATA', 'TPCH_SF1', 'LINEITEM',
'TEST', 'PUBLIC', 'LINEITEM');
create or replace procedure INFER_DATA_TYPES(SOURCE_QUERY string,
DATABASE_OLD string,
SCHEMA_OLD string,
TABLE_OLD string,
DATABASE_NEW string,
SCHEMA_NEW string,
TABLE_NEW string)
returns string
language javascript
as
$$
/****************************************************************************************************
* *
* DataType Classes
* *
****************************************************************************************************/
class Query{
constructor(statement){
this.statement = statement;
}
}
class DataType {
constructor(db, schema, table, column, sourceQuery) {
this.db = db;
this.schema = schema;
this.table = table;
this.sourceQuery = sourceQuery
this.column = column;
this.insert = '"@~COLUMN~@"';
this.totalCount = 0;
this.notNullCount = 0;
this.typeCount = 0;
this.blankCount = 0;
this.minTypeOf = 0.95;
this.minNotNull = 1.00;
}
setSQL(sqlTemplate){
this.sql = sqlTemplate;
this.sql = this.sql.replace(/@~DB~@/g, this.db);
this.sql = this.sql.replace(/@~SCHEMA~@/g, this.schema);
this.sql = this.sql.replace(/@~TABLE~@/g, this.table);
this.sql = this.sql.replace(/@~COLUMN~@/g, this.column);
}
getCounts(){
var rs;
rs = GetResultSet(this.sql);
rs.next();
this.totalCount = rs.getColumnValue("TOTAL_COUNT");
this.notNullCount = rs.getColumnValue("NON_NULL_COUNT");
this.typeCount = rs.getColumnValue("TO_TYPE_COUNT");
this.blankCount = rs.getColumnValue("BLANK");
}
isCorrectType(){
return (this.typeCount / (this.notNullCount - this.blankCount) >= this.minTypeOf);
}
isNotNull(){
return (this.notNullCount / this.totalCount >= this.minNotNull);
}
}
class TimestampType extends DataType{
constructor(db, schema, table, column, sourceQuery){
super(db, schema, table, column, sourceQuery)
this.syntax = "timestamp";
this.insert = 'try_multi_timestamp(trim("@~COLUMN~@"))';
this.sourceQuery = SOURCE_QUERY;
this.setSQL(GetCheckTypeSQL(this.insert, this.sourceQuery));
this.getCounts();
}
}
class IntegerType extends DataType{
constructor(db, schema, table, column, sourceQuery){
super(db, schema, table, column, sourceQuery)
this.syntax = "number(38,0)";
this.insert = 'try_to_number(trim("@~COLUMN~@"), 38, 0)';
this.setSQL(GetCheckTypeSQL(this.insert, this.sourceQuery));
this.getCounts();
}
}
class DoubleType extends DataType{
constructor(db, schema, table, column, sourceQuery){
super(db, schema, table, column, sourceQuery)
this.syntax = "double";
this.insert = 'try_to_double(trim("@~COLUMN~@"))';
this.setSQL(GetCheckTypeSQL(this.insert, this.sourceQuery));
this.getCounts();
}
}
class BooleanType extends DataType{
constructor(db, schema, table, column, sourceQuery){
super(db, schema, table, column, sourceQuery)
this.syntax = "boolean";
this.insert = 'try_to_boolean(trim("@~COLUMN~@"))';
this.setSQL(GetCheckTypeSQL(this.insert, this.sourceQuery));
this.getCounts();
}
}
// Catch all is STRING data type
class StringType extends DataType{
constructor(db, schema, table, column, sourceQuery){
super(db, schema, table, column, sourceQuery)
this.syntax = "string";
this.totalCount = 1;
this.notNullCount = 0;
this.typeCount = 1;
this.minTypeOf = 0;
this.minNotNull = 1;
}
}
/****************************************************************************************************
* *
* Main function *
* *
****************************************************************************************************/
var pass = 0;
var column;
var typeOf;
var ins = '';
var newTableDDL = '';
var insertDML = '';
var columnRS = GetResultSet(GetTableColumnsSQL(DATABASE_OLD, SCHEMA_OLD, TABLE_OLD));
while (columnRS.next()){
pass++;
if(pass > 1){
newTableDDL += ",\n";
insertDML += ",\n";
}
column = columnRS.getColumnValue("COLUMN_NAME");
typeOf = InferDataType(DATABASE_OLD, SCHEMA_OLD, TABLE_OLD, column, SOURCE_QUERY);
newTableDDL += '"' + typeOf.column + '" ' + typeOf.syntax;
ins = typeOf.insert;
insertDML += ins.replace(/@~COLUMN~@/g, typeOf.column);
}
return GetOpeningComments() +
GetDDLPrefixSQL(DATABASE_NEW, SCHEMA_NEW, TABLE_NEW) +
newTableDDL +
GetDDLSuffixSQL() +
GetDividerSQL() +
GetInsertPrefixSQL(DATABASE_NEW, SCHEMA_NEW, TABLE_NEW) +
insertDML +
GetInsertSuffixSQL(DATABASE_OLD, SCHEMA_OLD, TABLE_OLD) ;
/****************************************************************************************************
* *
* Helper functions *
* *
****************************************************************************************************/
function InferDataType(db, schema, table, column, sourceQuery){
var typeOf;
typeOf = new IntegerType(db, schema, table, column, sourceQuery);
if (typeOf.isCorrectType()) return typeOf;
typeOf = new DoubleType(db, schema, table, column, sourceQuery);
if (typeOf.isCorrectType()) return typeOf;
typeOf = new BooleanType(db, schema, table, column, sourceQuery); // May want to do a distinct and look for two values
if (typeOf.isCorrectType()) return typeOf;
typeOf = new TimestampType(db, schema, table, column, sourceQuery);
if (typeOf.isCorrectType()) return typeOf;
typeOf = new StringType(db, schema, table, column, sourceQuery);
if (typeOf.isCorrectType()) return typeOf;
return null;
}
/****************************************************************************************************
* *
* SQL Template Functions *
* *
****************************************************************************************************/
function GetCheckTypeSQL(insert, sourceQuery){
var sql =
`
select count(1) as TOTAL_COUNT,
count("@~COLUMN~@") as NON_NULL_COUNT,
count(${insert}) as TO_TYPE_COUNT,
sum(iff(trim("@~COLUMN~@")='', 1, 0)) as BLANK
--from "@~DB~@"."@~SCHEMA~@"."@~TABLE~@";
from (${sourceQuery})
`;
return sql;
}
function GetTableColumnsSQL(dbName, schemaName, tableName){
var sql =
`
select COLUMN_NAME
from ${dbName}.INFORMATION_SCHEMA.COLUMNS
where TABLE_CATALOG = '${dbName}' and
TABLE_SCHEMA = '${schemaName}' and
TABLE_NAME = '${tableName}'
order by ORDINAL_POSITION;
`;
return sql;
}
function GetOpeningComments(){
return `
/**************************************************************************************************************
* *
* Copy and paste into a worksheet to create the typed table and insert into the new table from the old one. *
* *
**************************************************************************************************************/
`;
}
function GetDDLPrefixSQL(db, schema, table){
var sql =
`
create or replace table "${db}"."${schema}"."${table}"
(
`;
return sql;
}
function GetDDLSuffixSQL(){
return "\n);";
}
function GetDividerSQL(){
return `
/**************************************************************************************************************
* *
* The SQL statement below this attempts to copy all rows from the string tabe to the typed table. *
* *
**************************************************************************************************************/
`;
}
function GetInsertPrefixSQL(db, schema, table){
var sql =
`\ninsert into "${db}"."${schema}"."${table}" select\n`;
return sql;
}
function GetInsertSuffixSQL(db, schema, table){
var sql =
`\nfrom "${db}"."${schema}"."${table}" ;`;
return sql;
}
//function GetInsertSuffixSQL(db, schema, table){
//var sql = '\nfrom "${db}"."${schema}"."${table}";';
//return sql;
//}
/****************************************************************************************************
* *
* SQL functions *
* *
****************************************************************************************************/
function GetResultSet(sql){
cmd1 = {sqlText: sql};
stmt = snowflake.createStatement(cmd1);
var rs;
rs = stmt.execute();
return rs;
}
function ExecuteNonQuery(queryString) {
var out = '';
cmd1 = {sqlText: queryString};
stmt = snowflake.createStatement(cmd1);
var rs;
rs = stmt.execute();
}
function ExecuteSingleValueQuery(columnName, queryString) {
var out;
cmd1 = {sqlText: queryString};
stmt = snowflake.createStatement(cmd1);
var rs;
try{
rs = stmt.execute();
rs.next();
return rs.getColumnValue(columnName);
}
catch(err) {
if (err.message.substring(0, 18) == "ResultSet is empty"){
throw "ERROR: No rows returned in query.";
} else {
throw "ERROR: " + err.message.replace(/\n/g, " ");
}
}
return out;
}
function ExecuteFirstValueQuery(queryString) {
var out;
cmd1 = {sqlText: queryString};
stmt = snowflake.createStatement(cmd1);
var rs;
try{
rs = stmt.execute();
rs.next();
return rs.getColumnValue(1);
}
catch(err) {
if (err.message.substring(0, 18) == "ResultSet is empty"){
throw "ERROR: No rows returned in query.";
} else {
throw "ERROR: " + err.message.replace(/\n/g, " ");
}
}
return out;
}
function getQuery(sql){
var cmd = {sqlText: sql};
var query = new Query(snowflake.createStatement(cmd));
try {
query.resultSet = query.statement.execute();
} catch (err) {
throw "ERROR: " + err.message.replace(/\n/g, " ");
}
return query;
}
$$;