Issues with Rename Attribute in Block Access Layer

[SaintNerevar]

Few corrections in BlockAccess::renameAttribute()

• A confusing IF block inside the loop.

if (attrcatRecId.block == -1 && attrcatRecId.slot == -1) { // Continue to search for more attributes continue; }

This doesn't seem right.

• Using a while loop would be simpler.
• The algorithm doesn't check for E_ATTREXIST case

The way it is right now, this algorithm is quite confusing. Attaching my implementation in case it helps.

  RecId defaultId{-1, -1};
  Attribute relationName;
  strcpy(relationName.strval, relName);
  RelCacheTable::setSearchIndex(0, &defaultId);
  RecId recId = ba_linearSearch(0, "RelName", relationName, EQ);

  if (recId.block == -1) return E_RELNOTEXIST;

  RelCacheTable::setSearchIndex(1, &defaultId);
  recId = ba_linearSearch(1, "RelName", relationName, EQ);
  RecId attrId{-1, -1};
  Attribute record[6];

  while (recId.block != -1) {
    RecBuffer attrBlk{recId.block};
    attrBlk.getRecord(record, recId.slot);

    if (strcmp(record[1].strval, oldName) == 0) attrId = recId;

    if (strcmp(record[1].strval, newName) == 0) return E_ATTREXIST;

    recId = ba_linearSearch(1, "RelName", relationName, EQ);
  }

  if (attrId.block == -1) return E_ATTRNOTEXIST;

  RecBuffer attrBlk{attrId.block};
  attrBlk.getRecord(record, attrId.slot);
  strcpy(record[1].strval, newName);
  attrBlk.setRecord(record, attrId.slot);

  return SUCCESS;

[gokulsreekumar]

Fixed, The algorithm in documentation is updated to the following:

int BlockAccess::renameAttribute(char *relName, char *oldName, char *newName) {
    // Search for the relation with name relName in relation catalog using Linear Search
    Attribute attrValueRelName;
    strcpy(attrValueRelName.sVal, relName);
        RecId searchIndex = {-1, -1};
        RelCacheTable::setSearchIndex(RELCAT_RELID, &searchIndex);
    RecId relcatRecId = linearSearch(RELCAT_RELID, "RelName", attrValueRelName, EQ);

    // If relation with name relName does not exits (relcatRecId == {-1,-1})
    //    return E_RELNOTEXIST;

    /*** 
        Iterating over all Attribute Catalog Entry record corresponding to relation to find the required attribute 
    ***/
    // Reset the Search Index by using RelCacheTable and setting value to {-1, -1}
    searchIndex = {-1, -1};
    RelCacheTable::setSearchIndex(ATTRCAT_RELID, &searchIndex);

    // Define RecId attrId {-1, -1} - used to check if an attribute of oldName exists or not.
    RecId attrId{-1, -1};
    Attribute attrcatEntryRecord[ATTRCAT_NO_ATTRS];
    while (true) {
        RecId attrcatEntryRecId = linearSearch(ATTRCAT_RELID, "RelName", relationName, EQ);

        if (attrcatEntryRecId.block == -1) {
            break;
        }

        // Get the attribute catalog record from the attribute catalog
        // Hint: instantiate RecBuffer Class with appropriate block number and use getRecord method to store the record into attrcatEntryRecord.

                // if (strcmp(attrcatEntryRecord[1].sVal, oldName) == 0) attrId = attrcatEntryRecId;

                // if (strcmp(attrcatEntryRecord[1].sVal, newName) == 0) return E_ATTREXIST;

    }

    // if (attrId.block == -1) return E_ATTRNOTEXIST;

    // Update the entry corresponding to the attribute in the Attribute Catalog Relation.
    /* Hint: Instantiate RecBuffer class by passing appropriate block number = attrId.block
        Get the record corresponding to the entry by using getRecord method by passing attrId.slot
        as argument.
        Use setRecord method to set the record back after updating the entry appropriately.
    */

    // return SUCCESS
}