describe.c

/*!
   \file db/drivers/describe.c

   \brief Low level OGR SQL driver

   (C) 2004-2009 by the GRASS Development Team
   This program is free software under the GNU General Public License
   (>=v2). Read the file COPYING that comes with GRASS for details.

   \author Radim Blazek
   \author Some updates by Martin Landa <landa.martin gmail.com>
 */

#include <grass/gis.h>
#include <grass/datetime.h>
#include <grass/dbmi.h>
#include <grass/glocale.h>

#include <ogr_api.h>

#include "globals.h"
#include "proto.h"

/*!
   \brief Describe table using driver

   \param table_name table name (as dbString)
   \param table[out] pointer to dbTable

   \return DB_OK on success
   \return DB_FAILED on failure
 */
int db__driver_describe_table(dbString *table_name, dbTable **table)
{
    int i, nlayers;
    OGRLayerH hLayer = NULL;
    OGRFeatureDefnH hFeatureDefn;

    /* get number of OGR layers in the datasource */
    nlayers = OGR_DS_GetLayerCount(hDs);

    /* find OGR layer */
    for (i = 0; i < nlayers; i++) {
        hLayer = OGR_DS_GetLayer(hDs, i);
        hFeatureDefn = OGR_L_GetLayerDefn(hLayer);
        if (G_strcasecmp((char *)OGR_FD_GetName(hFeatureDefn),
                         db_get_string(table_name)) == 0) {
            break;
        }
        hLayer = NULL;
    }

    if (hLayer == NULL) {
        db_d_append_error(_("OGR layer <%s> does not exist\n"),
                          db_get_string(table_name));
        db_d_report_error();
        return DB_FAILED;
    }

    G_debug(3, "->>");
    if (describe_table(hLayer, table, NULL) == DB_FAILED) {
        db_d_append_error(_("Unable to describe table\n"));
        db_d_report_error();
        return DB_FAILED;
    }

    return DB_OK;
}

/*!
   \brief Describe table

   If c is not NULL cur->cols and cur->ncols is also set
   cursor may be null

   \param hLayer OGR layer
   \param[put] table pointer to dbTable
   \param c pointer to cursor
 */
int describe_table(OGRLayerH hLayer, dbTable **table, cursor *c)
{
    int i, ncols, kcols, col;
    dbColumn *column;
    OGRFeatureDefnH hFeatureDefn;
    OGRFieldDefnH hFieldDefn;
    const char *fieldName, *fidcol;
    int ogrType;
    int *cols;

    G_debug(1, "describe_table()");

    hFeatureDefn = OGR_L_GetLayerDefn(hLayer);
    ncols = OGR_FD_GetFieldCount(hFeatureDefn);
    G_debug(2, "   ncols = %d (without fid column)", ncols);

    /* for some formats fid column is not defined, e.g. ESRI Shapefile */
    fidcol = OGR_L_GetFIDColumn(hLayer);
    G_debug(2, "   fidcol = %s", fidcol);

    /* identify known columns */
    cols = (int *)G_malloc(ncols * sizeof(int));
    kcols = 0;
    for (i = 0; i < ncols; i++) {
        hFieldDefn = OGR_FD_GetFieldDefn(hFeatureDefn, i);
        ogrType = OGR_Fld_GetType(hFieldDefn);
        fieldName = OGR_Fld_GetNameRef(hFieldDefn);

        if (ogrType != OFTInteger && ogrType != OFTInteger64 &&
            ogrType != OFTReal && ogrType != OFTString && ogrType != OFTDate &&
            ogrType != OFTTime && ogrType != OFTDateTime) {
            G_warning(
                _("OGR driver: column '%s', OGR type %d is not supported"),
                fieldName, ogrType);
            cols[i] = 0;
        }
        else {
            cols[i] = 1;
            kcols++;
        }
    }

    if (*fidcol)
        kcols++;
    G_debug(2, "   kcols = %d (including fid column)", kcols);

    /* allocate dbTable */
    if (!(*table = db_alloc_table(kcols))) {
        return DB_FAILED;
    }

    /* set the table name */
    /* TODO */
    db_set_table_name(*table, "");

    /* set the table description */
    db_set_table_description(*table, "");

    /* TODO */
    /*
       db_set_table_delete_priv_granted (*table);
       db_set_table_insert_priv_granted (*table);
       db_set_table_delete_priv_not_granted (*table);
       db_set_table_insert_priv_not_granted (*table);
     */

    if (*fidcol) {
        column = db_get_table_column(*table, 0);
        db_set_column_host_type(column, OFTInteger);
        db_set_column_sqltype(column, DB_SQL_TYPE_INTEGER);
        db_set_column_name(column, fidcol);
        db_set_column_length(column, 11); /* ??? */
        db_set_column_precision(column, 0);

        col = 1;
    }
    else {
        col = 0;
    }

    for (i = 0; i < ncols; i++, col++) {
        int sqlType = DB_SQL_TYPE_UNKNOWN;
        int size = 0, precision = 0 /* , scale */;

        hFieldDefn = OGR_FD_GetFieldDefn(hFeatureDefn, i);
        ogrType = OGR_Fld_GetType(hFieldDefn);
        fieldName = OGR_Fld_GetNameRef(hFieldDefn);

        if (!(cols[i])) {
            continue; /* unknown type */
        }

        switch (ogrType) {
        case OFTInteger:
        case OFTInteger64:
            sqlType = DB_SQL_TYPE_INTEGER;
            size = OGR_Fld_GetWidth(hFieldDefn); /* OK ? */
            precision = 0;
            if (ogrType == OFTInteger64)
                G_warning(_("Column '%s' : type int8 (bigint) is stored as "
                            "integer (4 bytes) "
                            "some data may be damaged"),
                          fieldName);
            break;

        case OFTReal:
            sqlType = DB_SQL_TYPE_DOUBLE_PRECISION;
            size = OGR_Fld_GetWidth(hFieldDefn); /* OK ? */
            precision = OGR_Fld_GetPrecision(hFieldDefn);
            break;

        case OFTString:
        case OFTDate:
        case OFTTime:
        case OFTDateTime:
            size = OGR_Fld_GetWidth(hFieldDefn);
            if (size > 0) {
                sqlType = DB_SQL_TYPE_CHARACTER;
            }
            else {
                sqlType = DB_SQL_TYPE_TEXT;
            }
            precision = 0;
            break;

        default:
            G_warning(_("Unknown type"));
            break;
        }

        G_debug(
            3,
            "   %d: field %d : ogrType = %d, name = %s, size=%d precision=%d",
            i, col, ogrType, fieldName, size, precision);

        column = db_get_table_column(*table, col);

        db_set_column_host_type(column, ogrType);
        db_set_column_sqltype(column, sqlType);
        db_set_column_name(column, fieldName);
        db_set_column_length(column, size);
        db_set_column_precision(column, precision);

        /* TODO
           scale = 0;
           db_set_column_scale (column, scale);
         */

        /* TODO */
        db_set_column_null_allowed(column);
        db_set_column_has_undefined_default_value(column);
        db_unset_column_use_default_value(column);

        /* TODO */
        /*
           db_set_column_select_priv_granted (column);
           db_set_column_update_priv_granted (column);
           db_set_column_update_priv_not_granted (column);
         */
    }

    if (c) {
        c->cols = cols;
        c->ncols = ncols;
    }
    else {
        G_free(cols);
    }

    return DB_OK;
}