Geografic-Information-System/db/drivers/postgres/describe.c

#include <grass/dbmi.h>
#include <grass/datetime.h>
#include "globals.h"
#include "proto.h"
#include <grass/glocale.h>

int db__driver_describe_table(dbString * table_name, dbTable ** table)
{
    dbString sql;
    PGresult *res;

    db_init_string(&sql);

    db_set_string(&sql, "select * from ");
    db_append_string(&sql, db_get_string(table_name));
    db_append_string(&sql, " where 1 = 0");

    res = PQexec(pg_conn, db_get_string(&sql));

    if (!res || PQresultStatus(res) != PGRES_TUPLES_OK) {
	append_error(db_get_string(&sql));
	append_error("\n");
	append_error(PQerrorMessage(pg_conn));
	report_error();
	PQclear(res);
	return DB_FAILED;
    }

    if (describe_table(res, table, NULL) == DB_FAILED) {
	append_error("Cannot describe table\n");
	report_error();
	PQclear(res);
	return DB_FAILED;
    }

    PQclear(res);

    return DB_OK;
}

/* describe table, if c is not NULL cur->cols and cur->ncols is also set */
int describe_table(PGresult * res, dbTable ** table, cursor * c)
{
    int i, ncols, kcols;
    int pgtype, gpgtype;
    char *fname;
    int sqltype, fsize, precision, scale;
    dbColumn *column;

    G_debug(3, "describe_table()");

    ncols = PQnfields(res);


    /* Count columns of known type */
    kcols = 0;
    for (i = 0; i < ncols; i++) {
	get_column_info(res, i, &pgtype, &gpgtype, &sqltype, &fsize);

	if (sqltype == DB_SQL_TYPE_UNKNOWN)
	    continue;

	kcols++;		/* known types */
    }

    G_debug(3, "kcols = %d", kcols);

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

    if (c) {
	c->ncols = kcols;
	c->cols = (int *)G_malloc(kcols * sizeof(int));
    }

    /* 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);
     */

    kcols = 0;
    for (i = 0; i < ncols; i++) {
	fname = PQfname(res, i);
	get_column_info(res, i, &pgtype, &gpgtype, &sqltype, &fsize);
	G_debug(3,
		"col: %s, kcols %d, pgtype : %d, gpgtype : %d, sqltype %d, fsize : %d",
		fname, kcols, pgtype, gpgtype, sqltype, fsize);

	/* PG types defined in globals.h (and pg_type.h) */
	if (sqltype == DB_SQL_TYPE_UNKNOWN) {
	    if (gpgtype == PG_TYPE_POSTGIS_GEOM) {
		G_warning(_("pg driver: PostGIS column '%s', type 'geometry'  will not be converted"),
			  fname);
		continue;
	    }
	    else {
		/* Warn, ignore and continue */
		G_warning(_("pg driver: column '%s', type %d  is not supported"),
			  fname, pgtype);
		continue;
	    }
	}

	if (gpgtype == PG_TYPE_INT8)
	    G_warning(_("column '%s' : type int8 (bigint) is stored as integer (4 bytes) "
		       "some data may be damaged"), fname);

	if (gpgtype == PG_TYPE_VARCHAR && fsize < 0) {
	    G_warning(_("column '%s' : type character varying is stored as varchar(250) "
		       "some data may be lost"), fname);
	    fsize = 250;
	}

	if (gpgtype == PG_TYPE_BOOL)
	    G_warning(_("column '%s' : type bool (boolean) is stored as char(1), values: 0 (false), "
		       "1 (true)"), fname);

	column = db_get_table_column(*table, kcols);

	db_set_column_name(column, fname);
	db_set_column_length(column, fsize);
	db_set_column_host_type(column, gpgtype);
	db_set_column_sqltype(column, sqltype);

	/* TODO */
	precision = 0;
	scale = 0;
	/*
	   db_set_column_precision (column, precision);
	   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[kcols] = i;
	}

	kcols++;
    }

    return DB_OK;
}

int get_column_info(PGresult * res, int col, int *pgtype, int *gpgtype,
		    int *sqltype, int *size)
{
    *pgtype = (int)PQftype(res, col);
    *gpgtype = get_gpg_type(*pgtype);

    /* Convert internal type to PG_TYPE_* */

    /* TODO: we should load field names from pg_type table instead of using copy of #defines */
    switch (*gpgtype) {
    case PG_TYPE_BIT:
    case PG_TYPE_INT2:
    case PG_TYPE_INT4:
    case PG_TYPE_INT8:
    case PG_TYPE_SERIAL:
    case PG_TYPE_OID:
	*sqltype = DB_SQL_TYPE_INTEGER;
	*size = PQfsize(res, col);
	break;

    case PG_TYPE_CHAR:
    case PG_TYPE_BPCHAR:
    case PG_TYPE_VARCHAR:
	*sqltype = DB_SQL_TYPE_CHARACTER;
	*size = PQfmod(res, col) - 4;	/* Looks strange but works, something better? */
	break;

    case PG_TYPE_TEXT:
	*sqltype = DB_SQL_TYPE_TEXT;
	break;

    case PG_TYPE_FLOAT4:
    case PG_TYPE_FLOAT8:
    case PG_TYPE_NUMERIC:
	*sqltype = DB_SQL_TYPE_DOUBLE_PRECISION;
	*size = PQfsize(res, col);
	break;

	/* I'm not sure if text length is correct for size */
    case PG_TYPE_DATE:
	*sqltype = DB_SQL_TYPE_DATE;
	*size = 10;		/* YYYY-MM-DD */
	break;

    case PG_TYPE_TIME:
	*sqltype = DB_SQL_TYPE_TIME;
	*size = 8;		/* HH:MM:SS */
	break;

    case PG_TYPE_TIMESTAMP:
	*sqltype = DB_SQL_TYPE_TIMESTAMP;
	*size = 22;		/* YYYY-MM-DD HH:MM:SS+TZ */
	break;

    case PG_TYPE_BOOL:
	*sqltype = DB_SQL_TYPE_CHARACTER;
	*size = 1;
	break;

    default:
	*sqltype = DB_SQL_TYPE_UNKNOWN;
	*size = 0;
    }

    return 0;
}

/* for given internal postgres type returns GRASS Postgres type (one of PG_TYPE_*) */
int get_gpg_type(int pgtype)
{
    int i;

    for (i = 0; i < pg_ntypes; i++) {
	if (pg_types[i][0] == pgtype)
	    return pg_types[i][1];
    }
    return PG_TYPE_UNKNOWN;
}