[Snowflake-jdbc]It hangs when get info from resetset object of connection.getMetadata().getColumns(...) - jdbc

Question

I try to test the jdbc connection of snowflake with codes below
Connection conn = .......
.......
ResultSet rs = conn.getMetaData().getColumns(**null**, "PUBLIC", "TAB1", null); // 1. set parameters to get metadata of table TAB1
while (rs.next()) { // 2. It hangs here if the first parameter is null in above liune; otherwise(set the corrent db name), it works fine
System.out.println( "precision:" + rs.getInt(7)
+ ",col type name:" + rs.getString(6)
+ ",col type:" + rs.getInt(5)
+ ",col name:" + rs.getString(4)
+ ",CHAR_OCTET_LENGTH:" + rs.getInt(16)
+ ",buf LENGTH:" + rs.getString(8)
+ ",SCALE:" + rs.getInt(9));
}
.......
I debug the codes above in Intellij IDEA, and find that the debugger can't get the details of the object, it always shows "Evaluating..."
The JDBC driver I used is snowflake-jdbc-3.12.5.jar
Is it a bug?

Answer 1

When the catalog (database) argument is null, the JDBC code effectively runs the following SQL, which you can verify in your Snowflake account's Query History UIs/Views:
show columns in account;
This is an expensive metadata query to run due to no filters and the wide requested breadth (columns across the entire account).
Depending on how many databases exist in your organization's account, it may require several minutes or upto an hour of execution to return back results, which explains the seeming "hang". On a simple test with about 50k+ tables dispersed across 100+ of databases and schemas, this took at least 15 minutes to return back results.
I debug the codes above in Intellij IDEA, and find that the debugger can't get the details of the object, it always shows "Evaluating..."
This may be a weirdness with your IDE, but in a pinch you can use the Dump Threads (Ctrl + Escape, or Ctrl + Break) option in IDEA to provide a single captured thread dump view. This should help show that the JDBC client thread isn't hanging (as in, its not locked or starved), it is only waiting on the server to send back results.

Answer 2

There is no issue with the 3.12.5 jar.I just tested the same version in Eclipse, I can inspect all the objects . Could be an issue with your IDE.
ResultSet columns = metaData.getColumns(null, null, "TESTTABLE123",null);
while (columns.next()){
System.out.print("Column name and size: "+columns.getString("COLUMN_NAME"));
System.out.print("("+columns.getInt("COLUMN_SIZE")+")");
System.out.println(" ");
System.out.println("COLUMN_DEF : "+columns.getString("COLUMN_DEF"));
System.out.println("Ordinal position: "+columns.getInt("ORDINAL_POSITION"));
System.out.println("Catalog: "+columns.getString("TABLE_CAT"));
System.out.println("Data type (integer value): "+columns.getInt("DATA_TYPE"));
System.out.println("Data type name: "+columns.getString("TYPE_NAME"));
System.out.println(" ");
}