MCOL-5215 Fix overflow of UNION operation involving DECIMAL datatypes.

When a UNION operation involving DECIMAL datatypes with scale and digits
before the decimal exceeds the currently supported maximum precision
of 38, we throw an error to the user:
"MCS-2060: Union operation exceeds maximum DECIMAL precision of 38".

This is until MCOL-5417 is implemented where ColumnStore will have
full parity with MariaDB server in terms of maximum supported DECIMAL
precision and scale of 65 and 38 digits respectively.

dbcon/execplan/calpontsystemcatalog.cpp

@@ -6393,12 +6393,13 @@ boost::any CalpontSystemCatalog::ColType::convertColumnData(const std::string& d
 }
 
 CalpontSystemCatalog::ColType CalpontSystemCatalog::ColType::convertUnionColType(
-    vector<CalpontSystemCatalog::ColType>& types)
+    vector<CalpontSystemCatalog::ColType>& types,
+    unsigned int& rc)
 {
   idbassert(types.size());
   CalpontSystemCatalog::ColType unionedType = types[0];
   for (uint64_t i = 1; i < types.size(); i++)
-    dataconvert::DataConvert::joinColTypeForUnion(unionedType, types[i]);
+    dataconvert::DataConvert::joinColTypeForUnion(unionedType, types[i], rc);
   return unionedType;
 }
 

dbcon/execplan/calpontsystemcatalog.h

@@ -306,7 +306,7 @@ class CalpontSystemCatalog : public datatypes::SystemCatalog
       return !(*this == t);
     }
 
-    static ColType convertUnionColType(std::vector<ColType>&);
+    static ColType convertUnionColType(std::vector<ColType>&, unsigned int&);
   };
 
   /** the structure of a table infomation

dbcon/joblist/jlf_tuplejoblist.cpp

@@ -5102,11 +5102,18 @@ SJSTEP unionQueries(JobStepVector& queries, uint64_t distinctUnionNum, JobInfo&
   unionStep->inputAssociation(jsaToUnion);
   unionStep->outputAssociation(jsa);
 
+  // This return code in the call to convertUnionColType() below would
+  // always be 0. This is because convertUnionColType() is also called
+  // in the connector code in getSelectPlan()/getGroupPlan() which handle
+  // the non-zero return code scenarios from this function call and error
+  // out, in which case, the execution does not even get to ExeMgr.
+  unsigned int dummyUnionedTypeRc = 0;
+
   // get unioned column types
   for (uint64_t j = 0; j < colCount; ++j)
   {
     CalpontSystemCatalog::ColType colType =
-        CalpontSystemCatalog::ColType::convertUnionColType(queryColTypes[j]);
+        CalpontSystemCatalog::ColType::convertUnionColType(queryColTypes[j], dummyUnionedTypeRc);
     types.push_back(colType.colDataType);
     csNums.push_back(colType.charsetNumber);
     scale.push_back(colType.scale);

dbcon/mysql/ha_mcs_execplan.cpp

@@ -6819,7 +6819,7 @@ int processFrom(bool& isUnion, SELECT_LEX& select_lex, gp_walk_info& gwi, SCSEP&
   bool unionSel = false;
   // UNION master unit check
   // Existed pushdown handlers won't get in this scope
-  // except UNION pushdown that is to come.
+  // MDEV-25080 Union pushdown would enter this scope
   // is_unit_op() give a segv for derived_handler's SELECT_LEX
   if (!isUnion && (!isSelectHandlerTop || isSelectLexUnit) && select_lex.master_unit()->is_unit_op())
   {
@@ -7414,8 +7414,6 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex, SCSEP& csep, bool i
     return rc;
   }
 
-  bool unionSel = (!isUnion && select_lex.master_unit()->is_unit_op()) ? true : false;
-
   gwi.clauseType = WHERE;
   if ((rc = processWhere(select_lex, gwi, csep, condStack)))
   {
@@ -7857,25 +7855,32 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex, SCSEP& csep, bool i
   // @bug4388 normalize the project coltypes for union main select list
   if (!csep->unionVec().empty())
   {
+    unsigned int unionedTypeRc = 0;
+
     for (uint32_t i = 0; i < gwi.returnedCols.size(); i++)
     {
       vector<CalpontSystemCatalog::ColType> coltypes;
 
       for (uint32_t j = 0; j < csep->unionVec().size(); j++)
       {
-        coltypes.push_back(dynamic_cast<CalpontSelectExecutionPlan*>(csep->unionVec()[j].get())
+        CalpontSelectExecutionPlan* unionCsep =
-                               ->returnedCols()[i]
+            dynamic_cast<CalpontSelectExecutionPlan*>(csep->unionVec()[j].get());
-                               ->resultType());
+        coltypes.push_back(unionCsep->returnedCols()[i]->resultType());
 
         // @bug5976. set hasAggregate true for the main column if
         // one corresponding union column has aggregate
-        if (dynamic_cast<CalpontSelectExecutionPlan*>(csep->unionVec()[j].get())
+        if (unionCsep->returnedCols()[i]->hasAggregate())
-                ->returnedCols()[i]
-                ->hasAggregate())
           gwi.returnedCols[i]->hasAggregate(true);
       }
 
-      gwi.returnedCols[i]->resultType(CalpontSystemCatalog::ColType::convertUnionColType(coltypes));
+      gwi.returnedCols[i]->resultType(CalpontSystemCatalog::ColType::convertUnionColType(coltypes, unionedTypeRc));
+
+      if (unionedTypeRc != 0)
+      {
+        gwi.parseErrorText = IDBErrorInfo::instance()->errorMsg(unionedTypeRc);
+        setError(gwi.thd, ER_CHECK_NOT_IMPLEMENTED, gwi.parseErrorText, gwi);
+        return ER_CHECK_NOT_IMPLEMENTED;
+      }
     }
   }
 
@@ -8044,6 +8049,8 @@ int getSelectPlan(gp_walk_info& gwi, SELECT_LEX& select_lex, SCSEP& csep, bool i
 
   SRCP minSc;  // min width projected column. for count(*) use
 
+  bool unionSel = (!isUnion && select_lex.master_unit()->is_unit_op()) ? true : false;
+
   // Group by list. not valid for union main query
   if (!unionSel)
   {
@@ -9681,25 +9688,32 @@ int getGroupPlan(gp_walk_info& gwi, SELECT_LEX& select_lex, SCSEP& csep, cal_gro
   // @bug4388 normalize the project coltypes for union main select list
   if (!csep->unionVec().empty())
   {
+    unsigned int unionedTypeRc = 0;
+
     for (uint32_t i = 0; i < gwi.returnedCols.size(); i++)
     {
       vector<CalpontSystemCatalog::ColType> coltypes;
 
       for (uint32_t j = 0; j < csep->unionVec().size(); j++)
       {
-        coltypes.push_back(dynamic_cast<CalpontSelectExecutionPlan*>(csep->unionVec()[j].get())
+        CalpontSelectExecutionPlan* unionCsep =
-                               ->returnedCols()[i]
+            dynamic_cast<CalpontSelectExecutionPlan*>(csep->unionVec()[j].get());
-                               ->resultType());
+        coltypes.push_back(unionCsep->returnedCols()[i]->resultType());
 
         // @bug5976. set hasAggregate true for the main column if
         // one corresponding union column has aggregate
-        if (dynamic_cast<CalpontSelectExecutionPlan*>(csep->unionVec()[j].get())
+        if (unionCsep->returnedCols()[i]->hasAggregate())
-                ->returnedCols()[i]
-                ->hasAggregate())
           gwi.returnedCols[i]->hasAggregate(true);
       }
 
-      gwi.returnedCols[i]->resultType(CalpontSystemCatalog::ColType::convertUnionColType(coltypes));
+      gwi.returnedCols[i]->resultType(CalpontSystemCatalog::ColType::convertUnionColType(coltypes, unionedTypeRc));
+
+      if (unionedTypeRc != 0)
+      {
+        gwi.parseErrorText = IDBErrorInfo::instance()->errorMsg(unionedTypeRc);
+        setError(gwi.thd, ER_CHECK_NOT_IMPLEMENTED, gwi.parseErrorText, gwi);
+        return ER_CHECK_NOT_IMPLEMENTED;
+      }
     }
   }
 

dbcon/mysql/ha_mcs_pushdown.cpp

@@ -738,7 +738,6 @@ int ha_mcs_group_by_handler::end_scan()
  *    thd - THD pointer.
  *    sel_lex - SELECT_LEX* that describes the query.
  *    sel_unit - SELECT_LEX_UNIT* that describes the query.
- *    Only one of sel_lex and sel_unit is not null.
  * RETURN:
  *    select_handler if possible
  *    NULL in other case
@@ -816,15 +815,15 @@ select_handler* create_columnstore_select_handler_(THD* thd, SELECT_LEX* sel_lex
   // or unsupported feature.
   ha_columnstore_select_handler* handler;
 
-  if (sel_unit && sel_lex)
+  if (sel_unit && sel_lex) // partial pushdown of the SELECT_LEX_UNIT
   {
     handler = new ha_columnstore_select_handler(thd, sel_lex, sel_unit);
   }
-  else if (sel_unit)
+  else if (sel_unit) // complete pushdown of the SELECT_LEX_UNIT
   {
     handler = new ha_columnstore_select_handler(thd, sel_unit);
   }
-  else
+  else // Query only has a SELECT_LEX, no SELECT_LEX_UNIT
   {
     handler = new ha_columnstore_select_handler(thd, sel_lex);
   }

mysql-test/columnstore/basic/r/mcol641-union.result

@@ -1,3 +1,5 @@
+# MCOL-641 Union Test Cases
+# Once MCOL-5417 is supported, the errored out queries below should be fixed.
 DROP DATABASE IF EXISTS mcol641_union_db;
 CREATE DATABASE mcol641_union_db;
 USE mcol641_union_db;
@@ -11,63 +13,52 @@ INSERT INTO cs1 values (99999999999999999999999999999999999999, 9999999999999999
 INSERT INTO cs1 values (-99999999999999999999999999999999999998, -9999999999999999999999999999.9999999998, -0.99999999999999999999999999999999999998);
 INSERT INTO cs1 values (-99999999999999999999999999999999999999, -9999999999999999999999999999.9999999999, -0.99999999999999999999999999999999999999);
 SELECT d1, d1, d2 FROM cs1 UNION SELECT d2, d3, d3 FROM cs1;
-d1	d1	d2
+ERROR 42000: The storage engine for the table doesn't support MCS-2060: Union operation exceeds maximum DECIMAL precision of 38.
-125.0000000000	125.00000000000000000000000000000000000000	1.25000000000000000000000000000000000000
--125.0000000000	-125.00000000000000000000000000000000000000	-1.25000000000000000000000000000000000000
-99999999999999999999999999999999999998.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
-99999999999999999999999999999999999999.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
--99999999999999999999999999999999999998.0000000000	-999999999999999999999999999.99999999999999999999999999999999999999	-999999999999999999999999999.99999999999999999999999999999999999999
--99999999999999999999999999999999999999.0000000000	-999999999999999999999999999.99999999999999999999999999999999999999	-999999999999999999999999999.99999999999999999999999999999999999999
-1.2500000000	0.12500000000000000000000000000000000000	0.12500000000000000000000000000000000000
--1.2500000000	-0.12500000000000000000000000000000000000	-0.12500000000000000000000000000000000000
-9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998	0.99999999999999999999999999999999999998
-9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999	0.99999999999999999999999999999999999999
--9999999999999999999999999999.9999999998	-0.99999999999999999999999999999999999998	-0.99999999999999999999999999999999999998
--9999999999999999999999999999.9999999999	-0.99999999999999999999999999999999999999	-0.99999999999999999999999999999999999999
 SELECT d2, d3, d3 FROM cs1 UNION SELECT d1, d1, d2 FROM cs1;
-d2	d3	d3
+ERROR 42000: The storage engine for the table doesn't support MCS-2060: Union operation exceeds maximum DECIMAL precision of 38.
-1.2500000000	0.12500000000000000000000000000000000000	0.12500000000000000000000000000000000000
--1.2500000000	-0.12500000000000000000000000000000000000	-0.12500000000000000000000000000000000000
-9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998	0.99999999999999999999999999999999999998
-9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999	0.99999999999999999999999999999999999999
--9999999999999999999999999999.9999999998	-0.99999999999999999999999999999999999998	-0.99999999999999999999999999999999999998
--9999999999999999999999999999.9999999999	-0.99999999999999999999999999999999999999	-0.99999999999999999999999999999999999999
-125.0000000000	125.00000000000000000000000000000000000000	1.25000000000000000000000000000000000000
--125.0000000000	-125.00000000000000000000000000000000000000	-1.25000000000000000000000000000000000000
-99999999999999999999999999999999999998.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
-99999999999999999999999999999999999999.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
--99999999999999999999999999999999999998.0000000000	-999999999999999999999999999.99999999999999999999999999999999999999	-999999999999999999999999999.99999999999999999999999999999999999999
--99999999999999999999999999999999999999.0000000000	-999999999999999999999999999.99999999999999999999999999999999999999	-999999999999999999999999999.99999999999999999999999999999999999999
 SELECT d1, d2, d3 FROM cs1 UNION SELECT d1, d2, d3 FROM cs1;
 d1	d2	d3
-125	1.2500000000	0.12500000000000000000000000000000000000
 -125	-1.2500000000	-0.12500000000000000000000000000000000000
-99999999999999999999999999999999999998	9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998
-99999999999999999999999999999999999999	9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999
 -99999999999999999999999999999999999998	-9999999999999999999999999999.9999999998	-0.99999999999999999999999999999999999998
 -99999999999999999999999999999999999999	-9999999999999999999999999999.9999999999	-0.99999999999999999999999999999999999999
+125	1.2500000000	0.12500000000000000000000000000000000000
+99999999999999999999999999999999999998	9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998
+99999999999999999999999999999999999999	9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999
 INSERT INTO cs2 VALUES (125, 1.25, 0.125);
 INSERT INTO cs2 values (99999999999999999999999999999999999998, 9999999999999999999999999999.9999999998, 0.99999999999999999999999999999999999998);
 INSERT INTO cs2 values (99999999999999999999999999999999999999, 9999999999999999999999999999.9999999999, 0.99999999999999999999999999999999999999);
 SELECT d1, d1, d2 FROM cs2 UNION SELECT d2, d3, d3 FROM cs2;
-d1	d1	d2
+ERROR 42000: The storage engine for the table doesn't support MCS-2060: Union operation exceeds maximum DECIMAL precision of 38.
-125.0000000000	125.00000000000000000000000000000000000000	1.25000000000000000000000000000000000000
-99999999999999999999999999999999999998.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
-99999999999999999999999999999999999999.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
-1.2500000000	0.12500000000000000000000000000000000000	0.12500000000000000000000000000000000000
-9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998	0.99999999999999999999999999999999999998
-9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999	0.99999999999999999999999999999999999999
 SELECT d2, d3, d3 FROM cs2 UNION SELECT d1, d1, d2 FROM cs2;
-d2	d3	d3
+ERROR 42000: The storage engine for the table doesn't support MCS-2060: Union operation exceeds maximum DECIMAL precision of 38.
-1.2500000000	0.12500000000000000000000000000000000000	0.12500000000000000000000000000000000000
-9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998	0.99999999999999999999999999999999999998
-9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999	0.99999999999999999999999999999999999999
-125.0000000000	125.00000000000000000000000000000000000000	1.25000000000000000000000000000000000000
-99999999999999999999999999999999999998.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
-99999999999999999999999999999999999999.0000000000	999999999999999999999999999.99999999999999999999999999999999999999	999999999999999999999999999.99999999999999999999999999999999999999
 SELECT d1, d2, d3 FROM cs2 UNION SELECT d1, d2, d3 FROM cs2;
 d1	d2	d3
 125	1.2500000000	0.12500000000000000000000000000000000000
 99999999999999999999999999999999999998	9999999999999999999999999999.9999999998	0.99999999999999999999999999999999999998
 99999999999999999999999999999999999999	9999999999999999999999999999.9999999999	0.99999999999999999999999999999999999999
+DROP TABLE cs1, cs2;
+CREATE TABLE cs1 (d1 DECIMAL(20, 0), d2 DECIMAL(20, 18), d3 DECIMAL(18, 18)) ENGINE=columnstore;
+CREATE TABLE cs2 (d1 DECIMAL(20, 0) UNSIGNED, d2 DECIMAL(20, 18) UNSIGNED, d3 DECIMAL(18, 18) UNSIGNED) ENGINE=columnstore;
+INSERT INTO cs1 VALUES (12345678901234567890, 12.345678901234567891, 0.123456789012345678);
+INSERT INTO cs1 VALUES (-12345678901234567890, -12.345678901234567891, -0.123456789012345678);
+INSERT INTO cs1 VALUES (99999999999999999999, 99.999999999999999999, 0.999999999999999999);
+INSERT INTO cs1 VALUES (-99999999999999999999, -99.999999999999999999, -0.999999999999999999);
+INSERT INTO cs2 VALUES (12345678901234567890, 12.345678901234567891, 0.123456789012345678);
+INSERT INTO cs2 VALUES (99999999999999999999, 99.999999999999999999, 0.999999999999999999);
+SELECT d1, d1, d2 FROM cs1 UNION SELECT d2, d3, d3 FROM cs1;
+d1	d1	d2
+-12.345678901234567891	-0.123456789012345678	-0.123456789012345678
+-12345678901234567890.000000000000000000	-12345678901234567890.000000000000000000	-12.345678901234567891
+-99.999999999999999999	-0.999999999999999999	-0.999999999999999999
+-99999999999999999999.000000000000000000	-99999999999999999999.000000000000000000	-99.999999999999999999
+12.345678901234567891	0.123456789012345678	0.123456789012345678
+12345678901234567890.000000000000000000	12345678901234567890.000000000000000000	12.345678901234567891
+99.999999999999999999	0.999999999999999999	0.999999999999999999
+99999999999999999999.000000000000000000	99999999999999999999.000000000000000000	99.999999999999999999
+SELECT d1, d1, d2 FROM cs2 UNION SELECT d2, d3, d3 FROM cs2;
+d1	d1	d2
+12.345678901234567891	0.123456789012345678	0.123456789012345678
+12345678901234567890.000000000000000000	12345678901234567890.000000000000000000	12.345678901234567891
+99.999999999999999999	0.999999999999999999	0.999999999999999999
+99999999999999999999.000000000000000000	99999999999999999999.000000000000000000	99.999999999999999999
 DROP DATABASE mcol641_union_db;

mysql-test/columnstore/basic/t/mcol641-union.test

@@ -1,5 +1,8 @@
 -- source ../include/have_columnstore.inc
 
+--echo # MCOL-641 Union Test Cases
+--echo # Once MCOL-5417 is supported, the errored out queries below should be fixed.
+
 --disable_warnings
 DROP DATABASE IF EXISTS mcol641_union_db;
 --enable_warnings
@@ -19,17 +22,38 @@ INSERT INTO cs1 values (99999999999999999999999999999999999999, 9999999999999999
 INSERT INTO cs1 values (-99999999999999999999999999999999999998, -9999999999999999999999999999.9999999998, -0.99999999999999999999999999999999999998);
 INSERT INTO cs1 values (-99999999999999999999999999999999999999, -9999999999999999999999999999.9999999999, -0.99999999999999999999999999999999999999);
 
+--error ER_CHECK_NOT_IMPLEMENTED
 SELECT d1, d1, d2 FROM cs1 UNION SELECT d2, d3, d3 FROM cs1;
+--error ER_CHECK_NOT_IMPLEMENTED
 SELECT d2, d3, d3 FROM cs1 UNION SELECT d1, d1, d2 FROM cs1;
+--sorted_result
 SELECT d1, d2, d3 FROM cs1 UNION SELECT d1, d2, d3 FROM cs1;
 
 INSERT INTO cs2 VALUES (125, 1.25, 0.125);
 INSERT INTO cs2 values (99999999999999999999999999999999999998, 9999999999999999999999999999.9999999998, 0.99999999999999999999999999999999999998);
 INSERT INTO cs2 values (99999999999999999999999999999999999999, 9999999999999999999999999999.9999999999, 0.99999999999999999999999999999999999999);
 
+--error ER_CHECK_NOT_IMPLEMENTED
 SELECT d1, d1, d2 FROM cs2 UNION SELECT d2, d3, d3 FROM cs2;
+--error ER_CHECK_NOT_IMPLEMENTED
 SELECT d2, d3, d3 FROM cs2 UNION SELECT d1, d1, d2 FROM cs2;
+--sorted_result
 SELECT d1, d2, d3 FROM cs2 UNION SELECT d1, d2, d3 FROM cs2;
 
+DROP TABLE cs1, cs2;
+CREATE TABLE cs1 (d1 DECIMAL(20, 0), d2 DECIMAL(20, 18), d3 DECIMAL(18, 18)) ENGINE=columnstore;
+CREATE TABLE cs2 (d1 DECIMAL(20, 0) UNSIGNED, d2 DECIMAL(20, 18) UNSIGNED, d3 DECIMAL(18, 18) UNSIGNED) ENGINE=columnstore;
+INSERT INTO cs1 VALUES (12345678901234567890, 12.345678901234567891, 0.123456789012345678);
+INSERT INTO cs1 VALUES (-12345678901234567890, -12.345678901234567891, -0.123456789012345678);
+INSERT INTO cs1 VALUES (99999999999999999999, 99.999999999999999999, 0.999999999999999999);
+INSERT INTO cs1 VALUES (-99999999999999999999, -99.999999999999999999, -0.999999999999999999);
+INSERT INTO cs2 VALUES (12345678901234567890, 12.345678901234567891, 0.123456789012345678);
+INSERT INTO cs2 VALUES (99999999999999999999, 99.999999999999999999, 0.999999999999999999);
+
+--sorted_result
+SELECT d1, d1, d2 FROM cs1 UNION SELECT d2, d3, d3 FROM cs1;
+--sorted_result
+SELECT d1, d1, d2 FROM cs2 UNION SELECT d2, d3, d3 FROM cs2;
+
 # Clean UP
 DROP DATABASE mcol641_union_db;

utils/dataconvert/dataconvert.cpp

@@ -2934,7 +2934,8 @@ int64_t DataConvert::stringToTime(const string& data)
 }
 
 void DataConvert::joinColTypeForUnion(datatypes::SystemCatalog::TypeHolderStd& unionedType,
-                                      const datatypes::SystemCatalog::TypeHolderStd& type)
+                                      const datatypes::SystemCatalog::TypeHolderStd& type,
+                                      unsigned int& rc)
 {
   // limited support for VARBINARY, no implicit conversion.
   if (type.colDataType == datatypes::SystemCatalog::VARBINARY ||
@@ -2974,6 +2975,19 @@ void DataConvert::joinColTypeForUnion(datatypes::SystemCatalog::TypeHolderStd& u
         case datatypes::SystemCatalog::UBIGINT:
         case datatypes::SystemCatalog::UDECIMAL:
 
+          if (type.scale != 0)
+          {
+            const unsigned int digitsBeforeDecimal = type.precision - type.scale;
+            const unsigned int digitsBeforeDecimalUnion = unionedType.precision - unionedType.scale;
+
+            if ((std::max(digitsBeforeDecimal, digitsBeforeDecimalUnion) +
+                 std::max(type.scale, unionedType.scale)) > datatypes::INT128MAXPRECISION)
+            {
+              rc = logging::ERR_UNION_DECIMAL_OVERFLOW;
+              return;
+            }
+          }
+
           unionedType.precision = std::max(type.precision, unionedType.precision);
           unionedType.scale = std::max(type.scale, unionedType.scale);
 

utils/dataconvert/dataconvert.h

@@ -1290,7 +1290,8 @@ class DataConvert
   EXPORT static int64_t stringToTime(const std::string& data);
   // bug4388, union type conversion
   EXPORT static void joinColTypeForUnion(datatypes::SystemCatalog::TypeHolderStd& unionedType,
-                                         const datatypes::SystemCatalog::TypeHolderStd& type);
+                                         const datatypes::SystemCatalog::TypeHolderStd& type,
+                                         unsigned int& rc);
 
   static boost::any StringToBit(const datatypes::SystemCatalog::TypeAttributesStd& colType,
                                 const datatypes::ConvertFromStringParam& prm, const std::string& dataOrig,

utils/loggingcpp/ErrorMessage.txt

@@ -106,6 +106,8 @@
 2058    ERR_DISKAGG_OVERFLOW1 The hash function used produces a lot of hash collisions (1).
 2059    ERR_DISKAGG_OVERFLOW2 The hash function used produces a lot of hash collisions (2).
 
+2060	ERR_UNION_DECIMAL_OVERFLOW	Union operation exceeds maximum DECIMAL precision of 38.
+
 # Sub-query errors
 3001	ERR_NON_SUPPORT_SUB_QUERY_TYPE	This subquery type is not supported yet.
 3002	ERR_MORE_THAN_1_ROW	Subquery returns more than 1 row.