Fix MCOL 4632 and 4648 and further issues when casting to [U]BIGINT.

[phoeinx]

This PR fixes MCOL-4632 and MCOL-4648 and some other casting issues that I found while investigating both issues.

Why?

We use uintX_t constants to mark NULL values in result rows. E.g. in storage/columnstore/columnstore/utils/funcexp/funcexp.cpp l.394:

case CalpontSystemCatalog::UBIGINT:
      {
        uint64_t val = expression[i]->getUintVal(row, isNull);

         if (isNull)
          row.setUintField<8>(UBIGINTNULL, expression[i]->outputIndex());
        else
          row.setUintField<8>(val, expression[i]->outputIndex());

        break;
      }

If isNull gets set by getUintVal() we write UBIGINTNULL into the result row. If however val equals UBIGINTNULL (or 2^64 - 2) the output row also gets written with UBIGINTNULL and later on wrongly displayed as NULL and not with the expected numeric value of 2^64 - 2.

At the core of the issue is that we cannot store the whole range of [U]BIGINTs, because we have blocked some values by constant markers. It is not possible to insert values which are assigned constant markers into a BIGINT column (this is covered by a Out of range value for column error), but it is possible that CAST operation results take on the blocked values and are then wrongly/unexpectedly displayed as NULL.

Besides the issues from casting DECIMAL->BIGINT and DECIMAL->UBIGINT, I've also been able to find the same issue for - - UBIGINT->BIGINT

• TEXT/VARCHAR/etc. -> BIGINT/UBIGINT
• DOUBLE-> BIGINT/UBIGINT.

(All cases are documented in the mcol_4632 and mcol_4648 files in mysql-test/columnstore/bugfixes.)

How?

Main changes are in func_cast.cpp where for Func_cast_signed::getIntVal() and Func_cast_unsigned::getUintVal() I checked and updated every switch case to include a check for unallowed return values which are now encoded as joblist::MIN_MCS_BIGINT and joblist::MAX_MCS_UBIGINT.

Update: The previously described approach would have been the preferred way to ensure consistency. (Float values were already handled that way, meaning that one in the current version cannot cast to neither [U]BIGINTEMPTYROW nor [U]BIGINTNULL. However, as the EMPTYROW constant gets displayed as the correct INT value, there are some regression tests expecting to be able to cast to the EMPTYROW constant. (And some tests actually expecting a cast to NULL, but we are going to fix these at least.)

Therefore the new approach will be to allow casting to EMPTYROW constants from all datatypes (including floats) and disallow casting to NULL constants. All of this again handled in Func_cast_signed::getIntVal() and Func_cast_unsigned::getUintVal() and the respective casting methods per type.

Testing?

All cases are tested with regression tests inmcol_4632 and mcol_4648 files in mysql-test/columnstore/bugfixes.