rtpostgis.c

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/*
 *
 * WKTRaster - Raster Types for PostGIS
 * http://trac.osgeo.org/postgis/wiki/WKTRaster
 *
 * Copyright (C) 2011-2013 Regents of the University of California
 *   <bkpark@ucdavis.edu>
 * Copyright (C) 2010-2011 Jorge Arevalo <jorge.arevalo@deimos-space.com>
 * Copyright (C) 2010-2011 David Zwarg <dzwarg@azavea.com>
 * Copyright (C) 2009-2011 Pierre Racine <pierre.racine@sbf.ulaval.ca>
 * Copyright (C) 2009-2011 Mateusz Loskot <mateusz@loskot.net>
 * Copyright (C) 2008-2009 Sandro Santilli <strk@kbt.io>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 */
 
/***************************************************************
 * Some rules for returning NOTICE or ERROR...
 *
 * Send an ERROR like:
 *
 * elog(ERROR, "RASTER_out: Could not deserialize raster");
 *
 * only when:
 *
 * -something wrong happen with memory,
 * -a function got an invalid argument ('3BUI' as pixel type) so that no row can
 * be processed
 *
 * *** IMPORTANT: elog(ERROR, ...) does NOT return to calling function ***
 *
 * Send a NOTICE like:
 *
 * elog(NOTICE, "Invalid band index (must use 1-based). Returning NULL");
 *
 * when arguments (e.g. x, y, band) are NULL or out of range so that some or
 * most rows can be processed anyway
 *
 * in this case,
 * for SET functions or function normally returning a modified raster, return
 * the original raster
 * for GET functions, return NULL
 * try to deduce a valid parameter value if it makes sence (e.g. out of range
 * index for addBand)
 *
 * Do not put the name of the faulty function for NOTICEs, only with ERRORs.
 *
 ****************************************************************/
 
/******************************************************************************
 * Some notes on memory management...
 *
 * Every time a SQL function is called, PostgreSQL creates a  new memory context.
 * So, all the memory allocated with palloc/repalloc in that context is
 * automatically free'd at the end of the function. If you want some data to
 * live between function calls, you have 2 options:
 *
 * - Use fcinfo->flinfo->fn_mcxt contex to store the data (by pointing the
 *   data you want to keep with fcinfo->flinfo->fn_extra)
 * - Use SRF funcapi, and storing the data at multi_call_memory_ctx (by pointing
 *   the data you want to keep with funcctx->user_fctx. funcctx is created by
 *   funcctx = SPI_FIRSTCALL_INIT()). Recommended way in functions returning rows,
 *   like RASTER_dumpAsPolygons (see section 34.9.9 at
 *   http://www.postgresql.org/docs/8.4/static/xfunc-c.html).
 *
 * But raster code follows the same philosophy than the rest of PostGIS: keep
 * memory as clean as possible. So, we free all allocated memory.
 *
 * TODO: In case of functions returning NULL, we should free the memory too.
 *****************************************************************************/
 
/******************************************************************************
 * Notes for use of PG_DETOAST_DATUM(), PG_DETOAST_DATUM_SLICE()
 *   and PG_DETOAST_DATUM_COPY()
 *
 * When ONLY getting raster (not band) metadata, use PG_DETOAST_DATUM_SLICE()
 *   as it is generally quicker to get only the chunk of memory that contains
 *   the raster metadata.
 *
 *   Example: PG_DETOAST_DATUM_SLICE(PG_GETARG_DATUM(0), 0,
 *     sizeof(struct rt_raster_serialized_t))
 *
 * When ONLY setting raster or band(s) metadata OR reading band data, use
 *   PG_DETOAST_DATUM() as rt_raster_deserialize() allocates local memory
 *   for the raster and band(s) metadata.
 *
 *   Example: PG_DETOAST_DATUM(PG_GETARG_DATUM(0))
 *
 * When SETTING band pixel values, use PG_DETOAST_DATUM_COPY().  This is
 *   because band data (not metadata) is just a pointer to the correct
 *   memory location in the detoasted datum.  What is returned from
 *   PG_DETOAST_DATUM() may or may not be a copy of the input datum.
 *
 *   From the comments in postgresql/src/include/fmgr.h...
 *
 *     pg_detoast_datum() gives you either the input datum (if not toasted)
 *     or a detoasted copy allocated with palloc().
 *
 *   From the mouth of Tom Lane...
 *   http://archives.postgresql.org/pgsql-hackers/2002-01/msg01289.php
 *
 *     PG_DETOAST_DATUM_COPY guarantees to give you a copy, even if the
 *     original wasn't toasted.  This allows you to scribble on the input,
 *     in case that happens to be a useful way of forming your result.
 *     Without a forced copy, a routine for a pass-by-ref datatype must
 *     NEVER, EVER scribble on its input ... because very possibly it'd
 *     be scribbling on a valid tuple in a disk buffer, or a valid entry
 *     in the syscache.
 *
 *   The key detail above is that the raster datatype is a varlena, a
 *     passed by reference datatype.
 *
 *   Example: PG_DETOAST_DATUM_COPY(PG_GETARG_DATUM(0))
 *
 * If in doubt, use PG_DETOAST_DATUM_COPY() as that guarantees that the input
 *   datum is copied for use.
 *****************************************************************************/
 
#include <postgres.h> /* for palloc */
#include <fmgr.h> /* for PG_MODULE_MAGIC */
#include "utils/guc.h"
#include "utils/memutils.h"
 
#include "../../postgis_config.h"
#include "lwgeom_pg.h"
 
#include "rtpostgis.h"
#include "rtpg_internal.h"
#include "stringlist.h"
#include "optionlist.h"
 
#ifndef __GNUC__
# define __attribute__ (x)
#endif
 
/*
 * This is required for builds against pgsql
 */
PG_MODULE_MAGIC;
 
/* Module load callback */
void _PG_init(void);
 
/* Module unload callback */
void _PG_fini(void);
 
#define RT_MSG_MAXLEN 256
 
 
/* ---------------------------------------------------------------- */
/*  Memory allocation / error reporting hooks                       */
/* ---------------------------------------------------------------- */
 
static void *
rt_pg_alloc(size_t size)
{
    void * result;
 
    POSTGIS_RT_DEBUGF(5, "rt_pgalloc(%ld) called", (long int) size);
 
    result = palloc(size);
 
    return result;
}
 
static void *
rt_pg_realloc(void *mem, size_t size)
{
    void * result;
 
    POSTGIS_RT_DEBUGF(5, "rt_pg_realloc(%ld) called", (long int) size);
 
    if (mem)
        result = repalloc(mem, size);
 
    else
        result = palloc(size);
 
    return result;
}
 
static void
rt_pg_free(void *ptr)
{
    POSTGIS_RT_DEBUG(5, "rt_pfree called");
    pfree(ptr);
}
 
static void rt_pg_error(const char *fmt, va_list ap)
  __attribute__(( format(printf,1,0) ));
 
static void
rt_pg_error(const char *fmt, va_list ap)
{
    char errmsg[RT_MSG_MAXLEN+1];
 
    vsnprintf (errmsg, RT_MSG_MAXLEN, fmt, ap);
 
    errmsg[RT_MSG_MAXLEN]='\0';
    ereport(ERROR, (errmsg_internal("%s", errmsg)));
}
 
static void rt_pg_notice(const char *fmt, va_list ap)
  __attribute__(( format(printf,1,0) ));
 
static void
rt_pg_notice(const char *fmt, va_list ap)
{
    char msg[RT_MSG_MAXLEN+1];
 
    vsnprintf (msg, RT_MSG_MAXLEN, fmt, ap);
 
    msg[RT_MSG_MAXLEN]='\0';
    ereport(NOTICE, (errmsg_internal("%s", msg)));
}
 
static void rt_pg_debug(const char *fmt, va_list ap)
  __attribute__(( format(printf,1,0) ));
 
static void
rt_pg_debug(const char *fmt, va_list ap)
{
    char msg[RT_MSG_MAXLEN+1];
 
    vsnprintf (msg, RT_MSG_MAXLEN, fmt, ap);
 
    msg[RT_MSG_MAXLEN]='\0';
    ereport(DEBUG1, (errmsg_internal("%s", msg)));
}
 
static char *
rt_pg_options(const char* varname)
{
        char optname[128];
        char *optvalue;
        snprintf(optname, 128, "postgis.%s", varname);
        /* GetConfigOptionByName(name, found_name, missing_ok) */
        optvalue = GetConfigOptionByName(optname, NULL, true);
        if (optvalue && strlen(optvalue) == 0)
                return NULL;
        else
                return optvalue;
}
 
/* ---------------------------------------------------------------- */
/*  GDAL allowed config options for VSI filesystems */
/* ---------------------------------------------------------------- */
 
stringlist_t *vsi_option_stringlist = NULL;
 
 
#if POSTGIS_GDAL_VERSION < 23
 
/*
* For older versions of GDAL we  have extracted the list of options
* that were available at the 2.2 release and use that
* as our set of allowed VSI network file options.
*/
static void
rt_pg_vsi_load_all_options(void)
{
        const char * gdaloption;
        const char * const gdaloptions[] = {
                "aws_access_key_id",
                "aws_https",
                "aws_max_keys",
                "aws_s3_endpoint",
                "aws_region",
                "aws_request_payer",
                "aws_secret_access_key",
                "aws_session_token",
                "aws_timestamp",
                "aws_virtual_hosting",
                "cpl_gs_timestamp",
                "cpl_gs_endpoint",
                "gs_secret_access_key",
                "gs_access_key_id",
                "goa2_client_id",
                "goa2_client_secret",
                "cpl_curl_enable_vsimem",
                "cpl_curl_gzip",
                "cpl_curl_verbose",
                "gdal_http_auth",
                "gdal_http_connecttimeout",
                "gdal_http_cookie",
                "gdal_http_header_file",
                "gdal_http_low_speed_time",
                "gdal_http_low_speed_limit",
                "gdal_http_max_retry",
                "gdal_http_netrc",
                "gdal_http_proxy",
                "gdal_http_proxyuserpwd",
                "gdal_http_retry_delay",
                "gdal_http_userpwd",
                "gdal_http_timeout",
                "gdal_http_unsafessl",
                "gdal_http_useragent",
                "gdal_disable_readdir_on_open",
                "gdal_proxy_auth",
                "curl_ca_bundle",
                "ssl_cert_file",
                "vsi_cache_size",
                "cpl_vsil_curl_use_head",
                "cpl_vsil_curl_use_s3_redirect",
                "cpl_vsil_curl_max_ranges",
                "cpl_vsil_curl_use_cache",
                "cpl_vsil_curl_allowed_filename",
                "cpl_vsil_curl_allowed_extensions",
                "cpl_vsil_curl_slow_get_size",
                "vsi_cache",
                "vsis3_chunk_size",
                NULL
        };
        const char * const * gdaloptionsptr = gdaloptions;
 
        vsi_option_stringlist = stringlist_create();
        while((gdaloption = *gdaloptionsptr++))
        {
                stringlist_add_string_nosort(vsi_option_stringlist, gdaloption);
        }
        stringlist_sort(vsi_option_stringlist);
}
 
#else /* POSTGIS_GDAL_VERSION < 23 */
 
/*
* For newer versions of GDAL the VSIGetFileSystemOptions() call returns
* all the allowed options for each VSI network file type, and we just have
* to keep the list of VSI types statically in rt_pg_vsi_load_all_options().
*/
static void
rt_pg_vsi_load_options(const char* vsiname, stringlist_t *s)
{
        CPLXMLNode *root, *optNode;
        const char *xml = VSIGetFileSystemOptions(vsiname);
        if (!xml) return;
 
        root = CPLParseXMLString(xml);
        if (!root) {
                elog(ERROR, "%s: Unable to read options for VSI %s", __func__, vsiname);
                return;
        }
        optNode = CPLSearchXMLNode(root, "Option");
        if (!optNode) {
                CPLDestroyXMLNode(root);
                elog(ERROR, "%s: Unable to find <Option> in VSI XML %s", __func__, vsiname);
                return;
        }
        while(optNode)
        {
                const char *option = CPLGetXMLValue(optNode, "name", NULL);
                if (option) {
                        char *optionstr = pstrdup(option);
                        char *ptr = optionstr;
                        /* The options parser used in rt_util_gdal_open()
                           lowercases keys, so we'll lower case our list
                           of options before storing them in the stringlist. */
                        while (*ptr) {
                                *ptr = tolower(*ptr);
                                ptr++;
                        }
                        elog(DEBUG4, "GDAL %s option: %s", vsiname, optionstr);
                        stringlist_add_string_nosort(s, optionstr);
                }
                optNode = optNode->psNext;
        }
        CPLDestroyXMLNode(root);
}
 
static void
rt_pg_vsi_load_all_options(void)
{
        const char * vsiname;
        const char * const vsilist[] = {
                "/vsicurl/",
                "/vsis3/",
                "/vsigs/",
                "/vsiaz/",
                "/vsioss/",
                "/vsihdfs/",
                "/vsiwebhdfs/",
                "/vsiswift/",
                "/vsiadls/",
                NULL
        };
        const char * const * vsilistptr = vsilist;
 
        vsi_option_stringlist = stringlist_create();
        while((vsiname = *vsilistptr++))
        {
                rt_pg_vsi_load_options(vsiname, vsi_option_stringlist);
        }
        stringlist_sort(vsi_option_stringlist);
}
 
#endif /* POSTGIS_GDAL_VERSION < 23 */
 
 
static bool
rt_pg_vsi_check_options(char **newval, void **extra, GucSource source)
{
        size_t olist_sz, i;
        char *olist[OPTION_LIST_SIZE];
        const char *found = NULL;
        char *newoptions;
 
        memset(olist, 0, sizeof(olist));
        if (!newval || !*newval)
                return false;
        newoptions = pstrdup(*newval);
 
        /* Cache the legal options if they aren't already loaded */
        if (!vsi_option_stringlist)
                rt_pg_vsi_load_all_options();
 
        elog(DEBUG5, "%s: processing VSI options: %s", __func__, newoptions);
        option_list_parse(newoptions, olist);
        olist_sz = option_list_length(olist);
        if (olist_sz % 2 != 0)
                return false;
 
        for (i = 0; i < olist_sz; i += 2)
        {
                found = stringlist_find(vsi_option_stringlist, olist[i]);
                if (!found)
                {
                        elog(WARNING, "'%s' is not a legal VSI network file option", olist[i]);
                        pfree(newoptions);
                        return false;
                }
        }
        return true;
}
 
 
/* ---------------------------------------------------------------- */
/*  PostGIS raster GUCs                                             */
/* ---------------------------------------------------------------- */
 
static char *gdal_datapath = NULL;
static char *gdal_vsi_options = NULL;
 
static char *gdal_enabled_drivers = NULL;
static bool enable_outdb_rasters = false;
 
/* ---------------------------------------------------------------- */
/*  Useful variables                                                */
/* ---------------------------------------------------------------- */
 
static char *env_postgis_gdal_enabled_drivers = NULL;
static char *boot_postgis_gdal_enabled_drivers = NULL;
static char *env_postgis_enable_outdb_rasters = NULL;
 
/* postgis.gdal_datapath */
static void
rtpg_assignHookGDALDataPath(const char *newpath, void *extra) {
        POSTGIS_RT_DEBUGF(4, "newpath = %s", newpath);
        POSTGIS_RT_DEBUGF(4, "gdaldatapath = %s", gdal_datapath);
 
        /* clear finder cache */
        CPLFinderClean();
 
        /* clear cached OSR */
        OSRCleanup();
 
        /* set GDAL_DATA */
        CPLSetConfigOption("GDAL_DATA", newpath);
        POSTGIS_RT_DEBUGF(4, "GDAL_DATA = %s", CPLGetConfigOption("GDAL_DATA", ""));
}
 
/* postgis.gdal_enabled_drivers */
static void
rtpg_assignHookGDALEnabledDrivers(const char *enabled_drivers, void *extra) {
        int enable_all = 0;
        int disable_all = 0;
        int vsicurl = 0;
 
        char **enabled_drivers_array = NULL;
        uint32_t enabled_drivers_count = 0;
        bool *enabled_drivers_found = NULL;
        char *gdal_skip = NULL;
 
        uint32_t i;
        uint32_t j;
 
        POSTGIS_RT_DEBUGF(4, "GDAL_SKIP = %s", CPLGetConfigOption("GDAL_SKIP", ""));
        POSTGIS_RT_DEBUGF(4, "enabled_drivers = %s", enabled_drivers);
 
        /* if NULL, nothing to do */
        if (enabled_drivers == NULL)
                return;
 
        elog(DEBUG4, "Enabling GDAL drivers: %s", enabled_drivers);
 
        /* destroy the driver manager */
        /* this is the only way to ensure GDAL_SKIP is recognized */
        GDALDestroyDriverManager();
        CPLSetConfigOption("GDAL_SKIP", NULL);
 
        /* force wrapper function to call GDALAllRegister() */
        rt_util_gdal_register_all(1);
 
        enabled_drivers_array = rtpg_strsplit(enabled_drivers, " ", &enabled_drivers_count);
        enabled_drivers_found = palloc(sizeof(bool) * enabled_drivers_count);
        memset(enabled_drivers_found, FALSE, sizeof(bool) * enabled_drivers_count);
 
        /* scan for keywords DISABLE_ALL and ENABLE_ALL */
        disable_all = 0;
        enable_all = 0;
        if (strstr(enabled_drivers, GDAL_DISABLE_ALL) != NULL) {
                for (i = 0; i < enabled_drivers_count; i++) {
                        if (strstr(enabled_drivers_array[i], GDAL_DISABLE_ALL) != NULL) {
                                enabled_drivers_found[i] = TRUE;
                                disable_all = 1;
                        }
                }
        }
        else if (strstr(enabled_drivers, GDAL_ENABLE_ALL) != NULL) {
                for (i = 0; i < enabled_drivers_count; i++) {
                        if (strstr(enabled_drivers_array[i], GDAL_ENABLE_ALL) != NULL) {
                                enabled_drivers_found[i] = TRUE;
                                enable_all = 1;
                        }
                }
        }
        else if (strstr(enabled_drivers, GDAL_VSICURL) != NULL) {
                for (i = 0; i < enabled_drivers_count; i++) {
                        if (strstr(enabled_drivers_array[i], GDAL_VSICURL) != NULL) {
                                enabled_drivers_found[i] = TRUE;
                                vsicurl = 1;
                        }
                }
        }
 
        if (!enable_all) {
                int found = 0;
                uint32_t drv_count = 0;
                rt_gdaldriver drv_set = rt_raster_gdal_drivers(&drv_count, 0);
 
                POSTGIS_RT_DEBUGF(4, "driver count = %d", drv_count);
 
                /* all other drivers than those in new drivers are added to GDAL_SKIP */
                for (i = 0; i < drv_count; i++) {
                        found = 0;
 
                        if (!disable_all) {
                                /* gdal driver found in enabled_drivers, continue to thorough search */
                                if (strstr(enabled_drivers, drv_set[i].short_name) != NULL) {
                                        /* thorough search of enabled_drivers */
                                        for (j = 0; j < enabled_drivers_count; j++) {
                                                /* driver found */
                                                if (strcmp(enabled_drivers_array[j], drv_set[i].short_name) == 0) {
                                                        enabled_drivers_found[j] = TRUE;
                                                        found = 1;
                                                }
                                        }
                                }
                        }
 
                        /* driver found, continue */
                        if (found)
                                continue;
 
                        /* driver not found, add to gdal_skip */
                        if (gdal_skip == NULL) {
                                gdal_skip = palloc(sizeof(char) * (strlen(drv_set[i].short_name) + 1));
                                gdal_skip[0] = '\0';
                        }
                        else {
                                gdal_skip = repalloc(
                                        gdal_skip,
                                        sizeof(char) * (
                                                strlen(gdal_skip) + 1 + strlen(drv_set[i].short_name) + 1
                                        )
                                );
                                strcat(gdal_skip, " ");
                        }
                        strcat(gdal_skip, drv_set[i].short_name);
                }
 
                for (i = 0; i < drv_count; i++) {
                        pfree(drv_set[i].short_name);
                        pfree(drv_set[i].long_name);
                        pfree(drv_set[i].create_options);
                }
                if (drv_count) pfree(drv_set);
 
        }
 
        for (i = 0; i < enabled_drivers_count; i++) {
                if (enabled_drivers_found[i])
                        continue;
 
                if (disable_all)
                        elog(WARNING, "%s set. Ignoring GDAL driver: %s", GDAL_DISABLE_ALL, enabled_drivers_array[i]);
                else if (enable_all)
                        elog(WARNING, "%s set. Ignoring GDAL driver: %s", GDAL_ENABLE_ALL, enabled_drivers_array[i]);
                else
                        elog(WARNING, "Unknown GDAL driver: %s", enabled_drivers_array[i]);
        }
 
        if (vsicurl)
                elog(WARNING, "%s set.", GDAL_VSICURL);
 
        /* destroy the driver manager */
        /* this is the only way to ensure GDAL_SKIP is recognized */
        GDALDestroyDriverManager();
 
        /* set GDAL_SKIP */
        POSTGIS_RT_DEBUGF(4, "gdal_skip = %s", gdal_skip);
        CPLSetConfigOption("GDAL_SKIP", gdal_skip);
        if (gdal_skip != NULL) pfree(gdal_skip);
 
        /* force wrapper function to call GDALAllRegister() */
        rt_util_gdal_register_all(1);
 
        pfree(enabled_drivers_array);
        pfree(enabled_drivers_found);
        POSTGIS_RT_DEBUGF(4, "GDAL_SKIP = %s", CPLGetConfigOption("GDAL_SKIP", ""));
}
 
/* postgis.enable_outdb_rasters */
static void
rtpg_assignHookEnableOutDBRasters(bool enable, void *extra) {
        /* do nothing for now */
}
 
 
/* Module load callback */
void
_PG_init(void) {
 
        bool boot_postgis_enable_outdb_rasters = false;
        MemoryContext old_context;
 
        /*
         * Change to context for memory allocation calls like palloc() in the
         * extension initialization routine
         */
        old_context = MemoryContextSwitchTo(TopMemoryContext);
 
        /*
         use POSTGIS_GDAL_ENABLED_DRIVERS to set the bootValue
         of GUC postgis.gdal_enabled_drivers
        */
        env_postgis_gdal_enabled_drivers = getenv("POSTGIS_GDAL_ENABLED_DRIVERS");
        if (env_postgis_gdal_enabled_drivers == NULL) {
                size_t sz = sizeof(char) * (strlen(GDAL_DISABLE_ALL) + 1);
                boot_postgis_gdal_enabled_drivers = palloc(sz);
                snprintf(boot_postgis_gdal_enabled_drivers, sz, "%s", GDAL_DISABLE_ALL);
        }
        else {
                boot_postgis_gdal_enabled_drivers = rtpg_trim(
                        env_postgis_gdal_enabled_drivers
                );
        }
        POSTGIS_RT_DEBUGF(
                4,
                "boot_postgis_gdal_enabled_drivers = %s",
                boot_postgis_gdal_enabled_drivers
        );
 
        /*
         use POSTGIS_ENABLE_OUTDB_RASTERS to set the bootValue
         of GUC postgis.enable_outdb_rasters
        */
        env_postgis_enable_outdb_rasters = getenv("POSTGIS_ENABLE_OUTDB_RASTERS");
        if (env_postgis_enable_outdb_rasters != NULL) {
                char *env = rtpg_trim(env_postgis_enable_outdb_rasters);
 
                /* out of memory */
                if (env == NULL) {
                        elog(ERROR, "_PG_init: Cannot process environmental variable: POSTGIS_ENABLE_OUTDB_RASTERS");
                        return;
                }
 
                if (strcmp(env, "1") == 0)
                        boot_postgis_enable_outdb_rasters = true;
 
                if (env != env_postgis_enable_outdb_rasters)
                        pfree(env);
        }
        POSTGIS_RT_DEBUGF(
                4,
                "boot_postgis_enable_outdb_rasters = %s",
                boot_postgis_enable_outdb_rasters ? "TRUE" : "FALSE"
        );
 
        /* Install liblwgeom handlers */
        pg_install_lwgeom_handlers();
 
        /* Install rtcore handlers */
        rt_set_handlers_options(rt_pg_alloc, rt_pg_realloc, rt_pg_free,
                rt_pg_error, rt_pg_debug, rt_pg_notice,
                rt_pg_options);
 
        /* Define custom GUC variables. */
        if ( postgis_guc_find_option("postgis.gdal_datapath") )
        {
                /* In this narrow case the previously installed GUC is tied to the callback in */
                /* the previously loaded library. Probably this is happening during an */
                /* upgrade, so the old library is where the callback ties to. */
                elog(WARNING, "'%s' is already set and cannot be changed until you reconnect", "postgis.gdal_datapath");
        }
        else
        {
                DefineCustomStringVariable(
                        "postgis.gdal_datapath", /* name */
                        "Path to GDAL data files.", /* short_desc */
                        "Physical path to directory containing GDAL data files (sets the GDAL_DATA config option).", /* long_desc */
                        &gdal_datapath, /* valueAddr */
                        NULL, /* bootValue */
                        PGC_SUSET, /* GucContext context */
                        0, /* int flags */
                        NULL, /* GucStringCheckHook check_hook */
                        rtpg_assignHookGDALDataPath, /* GucStringAssignHook assign_hook */
                        NULL  /* GucShowHook show_hook */
                );
        }
 
        if ( postgis_guc_find_option("postgis.gdal_enabled_drivers") )
        {
                /* In this narrow case the previously installed GUC is tied to the callback in */
                /* the previously loaded library. Probably this is happening during an */
                /* upgrade, so the old library is where the callback ties to. */
                elog(WARNING, "'%s' is already set and cannot be changed until you reconnect", "postgis.gdal_enabled_drivers");
        }
        else
        {
                DefineCustomStringVariable(
                        "postgis.gdal_enabled_drivers", /* name */
                        "Enabled GDAL drivers.", /* short_desc */
                        "List of enabled GDAL drivers by short name. To enable/disable all drivers, use 'ENABLE_ALL' or 'DISABLE_ALL' (sets the GDAL_SKIP config option).", /* long_desc */
                        &gdal_enabled_drivers, /* valueAddr */
                        boot_postgis_gdal_enabled_drivers, /* bootValue */
                        PGC_SUSET, /* GucContext context */
                        0, /* int flags */
                        NULL, /* GucStringCheckHook check_hook */
                        rtpg_assignHookGDALEnabledDrivers, /* GucStringAssignHook assign_hook */
                        NULL  /* GucShowHook show_hook */
                );
        }
 
        if ( postgis_guc_find_option("postgis.enable_outdb_rasters") )
        {
                /* In this narrow case the previously installed GUC is tied to the callback in */
                /* the previously loaded library. Probably this is happening during an */
                /* upgrade, so the old library is where the callback ties to. */
                elog(WARNING, "'%s' is already set and cannot be changed until you reconnect", "postgis.enable_outdb_rasters");
        }
        else
        {
                DefineCustomBoolVariable(
                        "postgis.enable_outdb_rasters", /* name */
                        "Enable Out-DB raster bands", /* short_desc */
                        "If true, rasters can access data located outside the database", /* long_desc */
                        &enable_outdb_rasters, /* valueAddr */
                        boot_postgis_enable_outdb_rasters, /* bootValue */
                        PGC_SUSET, /* GucContext context */
                        0, /* int flags */
                        NULL, /* GucBoolCheckHook check_hook */
                        rtpg_assignHookEnableOutDBRasters, /* GucBoolAssignHook assign_hook */
                        NULL  /* GucShowHook show_hook */
                );
        }
 
        if ( postgis_guc_find_option("postgis.gdal_vsi_options") )
        {
                elog(WARNING, "'%s' is already set and cannot be changed until you reconnect", "postgis.gdal_vsi_options");
        }
        else
        {
                DefineCustomStringVariable(
                        "postgis.gdal_vsi_options", /* name */
                        "VSI config options", /* short_desc */
                        "Set the config options to be used when opening /vsi/ network files", /* long_desc */
                        &gdal_vsi_options, /* valueAddr */
                        "", /* bootValue */
                        PGC_USERSET, /* GucContext context */
                        0, /* int flags */
                        rt_pg_vsi_check_options, /* GucStringCheckHook check_hook */
                        NULL, /* GucStringAssignHook assign_hook */
                        NULL  /* GucShowHook show_hook */
                );
        }
 
        /* Revert back to old context */
        MemoryContextSwitchTo(old_context);
}
 
/* Module unload callback */
void
_PG_fini(void) {
 
        MemoryContext old_context;
 
        old_context = MemoryContextSwitchTo(TopMemoryContext);
 
        /* Clean up */
        pfree(env_postgis_gdal_enabled_drivers);
        pfree(boot_postgis_gdal_enabled_drivers);
        pfree(env_postgis_enable_outdb_rasters);
 
        env_postgis_gdal_enabled_drivers = NULL;
        boot_postgis_gdal_enabled_drivers = NULL;
        env_postgis_enable_outdb_rasters = NULL;
 
        /* Revert back to old context */
        MemoryContextSwitchTo(old_context);
}