Ns_PdDbBestRowId

Overview

Send primary key to the client.

Syntax

    void Ns_PdDbBestRowId(void *handle, char *tableName);

Description

This function retrieves the primary key of a table from the database and sends this to the client. If a table has a primary key, AOLserver can perform row updates and deletes. If the best-row-id operation is successful, this function should call Ns_PdSendString with an OK_STATUS. If a best-row-id is found then call Ns_PdSendString with the column name; otherwise, call Ns_PdSendString with NO_BESTROWID. On failure this function should return an exception code with Ns_PdSendException.

Psuedo-code Example

    
    /* Things italicized would be your DBMS-specific structures and calls. */
    #define MAX_COLUMN_NAME 1024
    /* This would be a SQL statement to get the primary key */
    #define SQL_FINDKEY /* ... */ 
    void
    Ns_PdDbBestRowId(void *handle, char *tableName) {
        DBMSState *state = (DBMSState *)handle;
        Ns_PdRowInfo *bindRowInfo, *getRowInfo;
        static char tableColName[] = "name";
        char columnName[MAX_COLUMN_NAME];
        int i;
        int done = 0;
        int status = NS_ERROR;
        int getRowRet;
        Ns_PdLog(Trace, "bestrowid(%s):", tableName);
        columnName[0] = '\0';
        /* query for a primary key first */
        sprintf(state->sqlbuf, SQL_FINDKEY, tableName, "key1", 
    tableName); 
        for (i = 0; !done && (i DBMSExec(state, state->sqlbuf)) == DB_ROWS) {
                if ((bindRowInfo = DBMSBindRow(state)) != NULL) {
                    char *itemVal;
                    int itemSize;
                    int nameIndex;
                    if ((getRowInfo = Ns_PdNewRowInfo(Ns_PdGetRowInfoNumColumns(bindRowInfo)))
!= NULL) {
                        status = NS_OK;
                        if ((getRowRet = DBMSGetRow(state, getRowInfo)) == NS_OK) {
                            if ((nameIndex = Ns_PdFindRowInfoValue(bindRowInfo, 
                                           tableColName, strlen(tableColName))) == -1 ) {
                                Ns_PdLog(Error, "DbBestRowId:  NULL \"%s\" column in %s 
table, %s key.", 
                                        tableColName, tableName, i==0 ? "primary" : "secondary");
                            } else {
                                Ns_PdGetRowInfoItem(getRowInfo, nameIndex, &itemVal, 
&itemSize);
                                strcpy(columnName, itemVal);
                            }
                        } else {
                            if (i == 0) { /* if first try */
                                if (getRowRet != DB_END_DATA) {
                                    DBMSCancel(state);
                                }
                                /* no primary key was found so look for a secondary key */
                                sprintf(state->sqlbuf, SQL_FINDKEY, tableName, "key2", 
tableName);
                                done = 0;
                            } else { /* secondary key failed */
                                Ns_PdLog(Trace, "DbBestRowId: Primary and secondary key 
search failed.");
                                strcpy(columnName, NO_BESTROWID);
                            }
                        }
                        Ns_PdFreeRowInfo(getRowInfo, 0);
                    }
                    Ns_PdFreeRowInfo(bindRowInfo, 1);
                } 
            } 
        }
     
        DBMSCancel(state);
        if (status == NS_ERROR) {
            Ns_PdSendException(state->exceptionCode, 
    state->exceptionMsg);
        }  else {
            Ns_PdSendString(OK_STATUS);
            Ns_PdSendString(columnName);
        }
    }

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