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Ns_PdDbGetTableInfo

Overview

Send system catalog information about a table to the client.

Syntax

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

Description

This function should retrieve the system catalog information (columns, types, etc.) about a table and send this to the client.

Returning a successful status of DB_ROWS indicates that the SQL query was the type of query that returned rows (e.g., SELECT), rather than a manipulation statement that does not return rows. If the initial SQL select query returns a successful status of DB_ROWS, then this function should:

Ns_PdDbGetTableInfo() describes the table by sending back three columns of data, named "ColName," "ColType," and "NotNull" respectively. These column names are sent to the server with an Ns_PdSendRowInfo() call. Then, each column of the table is described by sending a 3-column row to the server, giving the name, type and nullability of the table's column. Again, Ns_PdSendRowInfo() is used to send this information to the AOL Server. The type is specified as a string (one of the types from Ns_PdDbGetTypes()). The nullability is specified as either the string "t" or "f".

Psuedo-code Example

    /* Things italicized would be your DBMS-specific structures and 
calls. */
    /* defined in nspd.h */ 
    typedef struct Ns_PdRowData {
    int elSize;
    char *elData;

} Ns_PdRowData; typedef struct Ns_PdRowInfo { int numColumns; Ns_PdRowData *rowData; }; void Ns_PdDbGetTableInfo(void *handle, char *tableName) { DBMSState *state = (DBMSState *) handle; Ns_PdRowInfo *getRowInfo, *bindRowInfo; int status = NS_ERROR; int getRowRet; /* Exec SQL and "select" data from a table */ Ns_PdLog(Trace, "gettableinfo(%s):", tableName); sprintf(state->sqlbuf, "select c.column_name, c.column_type, c.column_notnull" " from columns c, tables t" " where t.table_name = '%s'" " and c.column_member = t.table_type;", tableName); status = DBMDExec(state, state->sqlbuf); if (status == DB_ROWS) { if ((bindRowInfo = DBMSBindRow(state)) != NULL) { getRowInfo = Ns_PdNewRowInfo(Ns_PdGetRowInfoNumColumns(bindRowInfo)); if (getRowInfo != NULL) { status = NS_OK; Ns_PdSendString(OK_STATUS); Ns_PdSendRowInfo(bindRowInfo); /* sends list of column names */ while ((getRowRet = DBMSGetRow(handle, getRowInfo)) == NS_OK) { /* send row info */ Ns_PdSendRowInfo(getRowInfo); } Ns_PdSendData(END_DATA, strlen(END_DATA)); /* NULL row terminates rows */ if (getRowRet == DB_END_DATA) { status = NS_OK; } else { Ns_PdLog(Error, "GetTableInfo: incomplete data sent to client (table=%s)", tableName); } /* free the getRowInfo structure when done */ Ns_PdFreeRowInfo(getRowInfo, 0); } /* free the bindRowInfo data and structure when done */ Ns_PdFreeRowInfo(bindRowInfo, 1); } } if (status != NS_OK) { Ns_PdSendException(state->exceptionCode, state->exceptionMsg); } }

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