[KYLIN-4757] Impossible precision for decimal datatype in kylin if the source column is numeric in postgres

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: v3.1.0
• Fix Version/s: v3.1.1
• Component/s: RDBMS Source
• Labels: postgresql source-jdbc
• Skill Level: Newcomer (Easy) - Everyone can do this
• Assignee: Xiaoxiang Yu
• Reporter: André Luís da Rosa de Lima
• Created: 13/Sep/20 16:45
• Updated: 18/Oct/20 14:04
• Resolved: 28/Sep/20 01:44

Description

Using Postgres as data source, columns of datatype numeric without a explicitly set precision and scale become "decimal(256)" in kylin. 256 comes from the value of "kylin.source.hive.default-varchar-precision" (despite using jdbc as datasource). This causes an error when building a cube.

The problem can be fixed in "org.apache.kylin.source.jdbc.extensible.JdbcExplorer" class (https://github.com/apache/kylin/tree/ master/source-jdbc/src/main/java/org/apache/kylin/source/jdbc/extensible/JdbcExplorer.java#L111 )

The csize variable defined in line 96 receives the value 131089 from columns.getInt("COLUMN_SIZE");

I fixed it by modifying the following part in the source file starting after line 111:

int precision = (SqlUtil.isPrecisionApplicable(kylinType) && csize > 0) ? csize : -1;                
precision = Math.min(precision, KylinConfig.getInstanceFromEnv().getDefaultVarcharPrecision());                
int scale = (SqlUtil.isScaleApplicable(kylinType) && digits > 0) ? digits : -1;

to this:

 

int precision = (SqlUtil.isPrecisionApplicable(kylinType) && csize > 0) ? csize : -1;

int maxPrecision = precision;
if (kylinType.equals("char")) {
    maxPrecision = KylinConfig.getInstanceFromEnv().getDefaultCharPrecision();
} else if (kylinType.equals("varchar")) {
    maxPrecision = KylinConfig.getInstanceFromEnv().getDefaultVarcharPrecision();
} else if ((kylinType.equals("decimal") || kylinType.equals("numeric"))) {
    maxPrecision = KylinConfig.getInstanceFromEnv().getDefaultDecimalPrecision();
}
precision = Math.min(precision, maxPrecision);

int scale = (SqlUtil.isScaleApplicable(kylinType) && digits > 0) ? digits : -1;