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Comment:Clarify some comments and add assert() and testcase() macros to the replace-trigger recheck logic for ticket [c1e19e12046d23fe]
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SHA3-256: 8c0042bd5ccd83f8794d19cbb1ec7564584f0dce54bfebc0ada00b836aca065f
User & Date: drh 2019-10-26 16:38:49
Context
2019-10-26
17:08
Performance optimization on sqlite3GenerateConstraintChecks() - bypass the loop that checks each column for NOT NULL constraints if it is known in advance that the table has no NOT NULL constraints. check-in: e3c3f4d7 user: drh tags: trunk
16:38
Clarify some comments and add assert() and testcase() macros to the replace-trigger recheck logic for ticket [c1e19e12046d23fe] check-in: 8c0042bd user: drh tags: trunk
16:02
Fix a problem in the legacy ".explain on" formatting when it is used on a query with more than 8 output columns. check-in: 070b4982 user: drh tags: trunk
Changes
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Changes to src/insert.c.

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  ** recheck all of the uniqueness constraints after they have all run.
  ** But on the recheck, the resolution is OE_Abort instead of OE_Replace.
  **
  ** If replace triggers are a possibility, then
  **
  **   (1) Allocate register regTrigCnt and initialize it to zero.
  **       That register will count the number of replace triggers that
  **       fire.  Constraint recheck only occurs if the number if positive.
  **   (2) Initialize pTrigger to the set of all DELETE triggers.
  **   (3) Initialize addrRecheck and lblRecheckOk
  **
  ** The uniqueness rechecking code will create a series of tests to run
  ** in a second pass.  The addrRecheck and lblRecheckOk variables are
  ** used to link together these tests which are separated from each other
  ** in the generate bytecode.
  */
................................................................................
        break;
      }
      default: {
        int nConflictCk;   /* Number of opcodes in conflict check logic */

        assert( onError==OE_Replace );
        nConflictCk = sqlite3VdbeCurrentAddr(v) - addrConflictCk;


        if( regTrigCnt ){
          sqlite3MultiWrite(pParse);
          nReplaceTrig++;
        }
        sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
            regR, nPkField, 0, OE_Replace,
            (pIdx==pPk ? ONEPASS_SINGLE : ONEPASS_OFF), iThisCur);
................................................................................
            ** for the current row */
            sqlite3VdbeAddOp2(v, OP_IsNull, regIdx-1, lblRecheckOk);
            VdbeCoverage(v);
          }
          /* Copy the constraint check code from above, except change
          ** the constraint-ok jump destination to be the address of
          ** the next retest block */
          while( nConflictCk>0 && !db->mallocFailed ){
            VdbeOp x;    /* Conflict check opcode to copy */
            /* The sqlite3VdbeAddOp4() call might reallocate the opcode array.
            ** Hence, make a complete copy of the opcode, rather than using
            ** a pointer to the opcode. */
            x = *sqlite3VdbeGetOp(v, addrConflictCk);
            if( x.opcode!=OP_IdxRowid ){
              int p2;      /* New P2 value for copied conflict check opcode */
................................................................................
    sqlite3VdbeGoto(v, ipkTop);
    VdbeComment((v, "Do IPK REPLACE"));
    sqlite3VdbeJumpHere(v, ipkBottom);
  }

  /* Recheck all uniqueness constraints after replace triggers have run */
  testcase( regTrigCnt!=0 && nReplaceTrig==0 );

  if( nReplaceTrig ){
    sqlite3VdbeAddOp2(v, OP_IfNot, regTrigCnt, lblRecheckOk);VdbeCoverage(v);
    if( !pPk ){
      if( isUpdate ){
        sqlite3VdbeAddOp3(v, OP_Eq, regNewData, addrRecheck, regOldData);
        sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
        VdbeCoverage(v);







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  ** recheck all of the uniqueness constraints after they have all run.
  ** But on the recheck, the resolution is OE_Abort instead of OE_Replace.
  **
  ** If replace triggers are a possibility, then
  **
  **   (1) Allocate register regTrigCnt and initialize it to zero.
  **       That register will count the number of replace triggers that
  **       fire.  Constraint recheck only occurs if the number is positive.
  **   (2) Initialize pTrigger to the list of all DELETE triggers on pTab.
  **   (3) Initialize addrRecheck and lblRecheckOk
  **
  ** The uniqueness rechecking code will create a series of tests to run
  ** in a second pass.  The addrRecheck and lblRecheckOk variables are
  ** used to link together these tests which are separated from each other
  ** in the generate bytecode.
  */
................................................................................
        break;
      }
      default: {
        int nConflictCk;   /* Number of opcodes in conflict check logic */

        assert( onError==OE_Replace );
        nConflictCk = sqlite3VdbeCurrentAddr(v) - addrConflictCk;
        assert( nConflictCk>0 );
        testcase( nConflictCk>1 );
        if( regTrigCnt ){
          sqlite3MultiWrite(pParse);
          nReplaceTrig++;
        }
        sqlite3GenerateRowDelete(pParse, pTab, pTrigger, iDataCur, iIdxCur,
            regR, nPkField, 0, OE_Replace,
            (pIdx==pPk ? ONEPASS_SINGLE : ONEPASS_OFF), iThisCur);
................................................................................
            ** for the current row */
            sqlite3VdbeAddOp2(v, OP_IsNull, regIdx-1, lblRecheckOk);
            VdbeCoverage(v);
          }
          /* Copy the constraint check code from above, except change
          ** the constraint-ok jump destination to be the address of
          ** the next retest block */
          while( nConflictCk>0 ){
            VdbeOp x;    /* Conflict check opcode to copy */
            /* The sqlite3VdbeAddOp4() call might reallocate the opcode array.
            ** Hence, make a complete copy of the opcode, rather than using
            ** a pointer to the opcode. */
            x = *sqlite3VdbeGetOp(v, addrConflictCk);
            if( x.opcode!=OP_IdxRowid ){
              int p2;      /* New P2 value for copied conflict check opcode */
................................................................................
    sqlite3VdbeGoto(v, ipkTop);
    VdbeComment((v, "Do IPK REPLACE"));
    sqlite3VdbeJumpHere(v, ipkBottom);
  }

  /* Recheck all uniqueness constraints after replace triggers have run */
  testcase( regTrigCnt!=0 && nReplaceTrig==0 );
  assert( regTrigCnt!=0 || nReplaceTrig==0 );
  if( nReplaceTrig ){
    sqlite3VdbeAddOp2(v, OP_IfNot, regTrigCnt, lblRecheckOk);VdbeCoverage(v);
    if( !pPk ){
      if( isUpdate ){
        sqlite3VdbeAddOp3(v, OP_Eq, regNewData, addrRecheck, regOldData);
        sqlite3VdbeChangeP5(v, SQLITE_NOTNULL);
        VdbeCoverage(v);