mvt.c

Go to the documentation of this file.

/**********************************************************************
 *
 * PostGIS - Spatial Types for PostgreSQL
 * http://postgis.net
 *
 * PostGIS 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.
 *
 * PostGIS 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 PostGIS.  If not, see <http://www.gnu.org/licenses/>.
 *
 **********************************************************************
 *
 * Copyright (C) 2016-2017 Björn Harrtell <bjorn@wololo.org>
 *
 **********************************************************************/
 
#include "mvt.h"
#include "lwgeom_geos.h"
 
#ifdef HAVE_LIBPROTOBUF
 
#if POSTGIS_PGSQL_VERSION >= 94
#include "utils/jsonb.h"
#endif
 
#if POSTGIS_PGSQL_VERSION < 110
/* See trac ticket #3867 */
# define DatumGetJsonbP DatumGetJsonb
#endif
 
#include "uthash.h"
 
#define FEATURES_CAPACITY_INITIAL 50
 
enum mvt_cmd_id
{
        CMD_MOVE_TO = 1,
        CMD_LINE_TO = 2,
        CMD_CLOSE_PATH = 7
};
 
enum mvt_type
{
        MVT_POINT = 1,
        MVT_LINE = 2,
        MVT_RING = 3
};
 
struct mvt_kv_key
{
        char *name;
        uint32_t id;
        UT_hash_handle hh;
};
 
struct mvt_kv_string_value
{
        char *string_value;
        uint32_t id;
        UT_hash_handle hh;
};
 
struct mvt_kv_float_value
{
        float float_value;
        uint32_t id;
        UT_hash_handle hh;
};
 
struct mvt_kv_double_value
{
        double double_value;
        uint32_t id;
        UT_hash_handle hh;
};
 
struct mvt_kv_uint_value
{
        uint64_t uint_value;
        uint32_t id;
        UT_hash_handle hh;
};
 
struct mvt_kv_sint_value
{
        int64_t sint_value;
        uint32_t id;
        UT_hash_handle hh;
};
 
struct mvt_kv_bool_value
{
        protobuf_c_boolean bool_value;
        uint32_t id;
        UT_hash_handle hh;
};
 
static inline uint32_t c_int(enum mvt_cmd_id id, uint32_t count)
{
        return (id & 0x7) | (count << 3);
}
 
static inline uint32_t p_int(int32_t value)
{
        return (value << 1) ^ (value >> 31);
}
 
static uint32_t encode_ptarray(__attribute__((__unused__)) mvt_agg_context *ctx,
                               enum mvt_type type, POINTARRAY *pa, uint32_t *buffer,
                               int32_t *px, int32_t *py)
{
        uint32_t offset = 0;
        uint32_t i, c = 0;
        int32_t dx, dy, x, y;
        const POINT2D *p;
 
        /* loop points and add to buffer */
        for (i = 0; i < pa->npoints; i++)
        {
                /* move offset for command */
                if (i == 0 || (i == 1 && type > MVT_POINT))
                        offset++;
                /* skip closing point for rings */
                if (type == MVT_RING && i == pa->npoints - 1)
                        break;
                p = getPoint2d_cp(pa, i);
                x = p->x;
                y = p->y;
                dx = x - *px;
                dy = y - *py;
                buffer[offset++] = p_int(dx);
                buffer[offset++] = p_int(dy);
                *px = x;
                *py = y;
                c++;
        }
 
        /* determine initial move and eventual line command */
        if (type == MVT_POINT)
        {
                /* point or multipoint, use actual number of point count */
                buffer[0] = c_int(CMD_MOVE_TO, c);
        }
        else
        {
                /* line or polygon, assume count 1 */
                buffer[0] = c_int(CMD_MOVE_TO, 1);
                /* line command with move point subtracted from count */
                buffer[3] = c_int(CMD_LINE_TO, c - 1);
        }
 
        /* add close command if ring */
        if (type == MVT_RING)
                buffer[offset++] = c_int(CMD_CLOSE_PATH, 1);
 
        return offset;
}
 
static uint32_t encode_ptarray_initial(mvt_agg_context *ctx,
                                       enum mvt_type type,
                                       POINTARRAY *pa, uint32_t *buffer)
{
        int32_t px = 0, py = 0;
        return encode_ptarray(ctx, type, pa, buffer, &px, &py);
}
 
static void encode_point(mvt_agg_context *ctx, LWPOINT *point)
{
        VectorTile__Tile__Feature *feature = ctx->feature;
        feature->type = VECTOR_TILE__TILE__GEOM_TYPE__POINT;
        feature->has_type = 1;
        feature->n_geometry = 3;
        feature->geometry = palloc(sizeof(*feature->geometry) * 3);
        encode_ptarray_initial(ctx, MVT_POINT, point->point, feature->geometry);
}
 
static void encode_mpoint(mvt_agg_context *ctx, LWMPOINT *mpoint)
{
        size_t c;
        VectorTile__Tile__Feature *feature = ctx->feature;
        // NOTE: inefficient shortcut LWMPOINT->LWLINE
        LWLINE *lwline = lwline_from_lwmpoint(mpoint->srid, mpoint);
        feature->type = VECTOR_TILE__TILE__GEOM_TYPE__POINT;
        feature->has_type = 1;
        c = 1 + lwline->points->npoints * 2;
        feature->geometry = palloc(sizeof(*feature->geometry) * c);
        feature->n_geometry = encode_ptarray_initial(ctx, MVT_POINT,
                lwline->points, feature->geometry);
}
 
static void encode_line(mvt_agg_context *ctx, LWLINE *lwline)
{
        size_t c;
        VectorTile__Tile__Feature *feature = ctx->feature;
        feature->type = VECTOR_TILE__TILE__GEOM_TYPE__LINESTRING;
        feature->has_type = 1;
        c = 2 + lwline->points->npoints * 2;
        feature->geometry = palloc(sizeof(*feature->geometry) * c);
        feature->n_geometry = encode_ptarray_initial(ctx, MVT_LINE,
                lwline->points, feature->geometry);
}
 
static void encode_mline(mvt_agg_context *ctx, LWMLINE *lwmline)
{
        uint32_t i;
        int32_t px = 0, py = 0;
        size_t c = 0, offset = 0;
        VectorTile__Tile__Feature *feature = ctx->feature;
        feature->type = VECTOR_TILE__TILE__GEOM_TYPE__LINESTRING;
        feature->has_type = 1;
        for (i = 0; i < lwmline->ngeoms; i++)
                c += 2 + lwmline->geoms[i]->points->npoints * 2;
        feature->geometry = palloc(sizeof(*feature->geometry) * c);
        for (i = 0; i < lwmline->ngeoms; i++)
                offset += encode_ptarray(ctx, MVT_LINE,
                        lwmline->geoms[i]->points,
                        feature->geometry + offset, &px, &py);
        feature->n_geometry = offset;
}
 
static void encode_poly(mvt_agg_context *ctx, LWPOLY *lwpoly)
{
        uint32_t i;
        int32_t px = 0, py = 0;
        size_t c = 0, offset = 0;
        VectorTile__Tile__Feature *feature = ctx->feature;
        feature->type = VECTOR_TILE__TILE__GEOM_TYPE__POLYGON;
        feature->has_type = 1;
        for (i = 0; i < lwpoly->nrings; i++)
                c += 3 + ((lwpoly->rings[i]->npoints - 1) * 2);
        feature->geometry = palloc(sizeof(*feature->geometry) * c);
        for (i = 0; i < lwpoly->nrings; i++)
                offset += encode_ptarray(ctx, MVT_RING,
                        lwpoly->rings[i],
                        feature->geometry + offset, &px, &py);
        feature->n_geometry = offset;
}
 
static void encode_mpoly(mvt_agg_context *ctx, LWMPOLY *lwmpoly)
{
        uint32_t i, j;
        int32_t px = 0, py = 0;
        size_t c = 0, offset = 0;
        LWPOLY *poly;
        VectorTile__Tile__Feature *feature = ctx->feature;
        feature->type = VECTOR_TILE__TILE__GEOM_TYPE__POLYGON;
        feature->has_type = 1;
        for (i = 0; i < lwmpoly->ngeoms; i++)
                for (j = 0; poly = lwmpoly->geoms[i], j < poly->nrings; j++)
                        c += 3 + ((poly->rings[j]->npoints - 1) * 2);
        feature->geometry = palloc(sizeof(*feature->geometry) * c);
        for (i = 0; i < lwmpoly->ngeoms; i++)
                for (j = 0; poly = lwmpoly->geoms[i], j < poly->nrings; j++)
                        offset += encode_ptarray(ctx, MVT_RING,
                                poly->rings[j], feature->geometry + offset,
                                &px, &py);
        feature->n_geometry = offset;
}
 
static void encode_geometry(mvt_agg_context *ctx, LWGEOM *lwgeom)
{
        int type = lwgeom->type;
 
        switch (type)
        {
        case POINTTYPE:
                return encode_point(ctx, (LWPOINT*)lwgeom);
        case LINETYPE:
                return encode_line(ctx, (LWLINE*)lwgeom);
        case POLYGONTYPE:
                return encode_poly(ctx, (LWPOLY*)lwgeom);
        case MULTIPOINTTYPE:
                return encode_mpoint(ctx, (LWMPOINT*)lwgeom);
        case MULTILINETYPE:
                return encode_mline(ctx, (LWMLINE*)lwgeom);
        case MULTIPOLYGONTYPE:
                return encode_mpoly(ctx, (LWMPOLY*)lwgeom);
        default: elog(ERROR, "encode_geometry: '%s' geometry type not supported",
                lwtype_name(type));
        }
}
 
static TupleDesc get_tuple_desc(mvt_agg_context *ctx)
{
        Oid tupType = HeapTupleHeaderGetTypeId(ctx->row);
        int32 tupTypmod = HeapTupleHeaderGetTypMod(ctx->row);
        TupleDesc tupdesc = lookup_rowtype_tupdesc(tupType, tupTypmod);
        return tupdesc;
}
 
static uint32_t get_key_index_with_size(mvt_agg_context *ctx, const char *name, size_t size)
{
        struct mvt_kv_key *kv;
        HASH_FIND(hh, ctx->keys_hash, name, size, kv);
        if (!kv)
                return UINT32_MAX;
        return kv->id;
}
 
static uint32_t add_key(mvt_agg_context *ctx, char *name)
{
        struct mvt_kv_key *kv;
        size_t size = strlen(name);
        kv = palloc(sizeof(*kv));
        kv->id = ctx->keys_hash_i++;
        kv->name = name;
        HASH_ADD_KEYPTR(hh, ctx->keys_hash, name, size, kv);
        return kv->id;
}
 
static void parse_column_keys(mvt_agg_context *ctx)
{
        uint32_t i, natts;
        bool geom_found = false;
 
        POSTGIS_DEBUG(2, "parse_column_keys called");
 
        ctx->column_cache.tupdesc = get_tuple_desc(ctx);
        natts = ctx->column_cache.tupdesc->natts;
 
        ctx->column_cache.column_keys_index = palloc(sizeof(uint32_t) * natts);
        ctx->column_cache.column_oid = palloc(sizeof(uint32_t) * natts);
        ctx->column_cache.values = palloc(sizeof(Datum) * natts);
        ctx->column_cache.nulls = palloc(sizeof(bool) * natts);
 
        for (i = 0; i < natts; i++)
        {
#if POSTGIS_PGSQL_VERSION < 110
                Oid typoid = getBaseType(ctx->column_cache.tupdesc->attrs[i]->atttypid);
                char *tkey = ctx->column_cache.tupdesc->attrs[i]->attname.data;
#else
                Oid typoid = getBaseType(ctx->column_cache.tupdesc->attrs[i].atttypid);
                char *tkey = ctx->column_cache.tupdesc->attrs[i].attname.data;
#endif
 
                ctx->column_cache.column_oid[i] = typoid;
#if POSTGIS_PGSQL_VERSION >= 94
                if (typoid == JSONBOID)
                {
                        ctx->column_cache.column_keys_index[i] = UINT32_MAX;
                        continue;
                }
#endif
 
                if (ctx->geom_name == NULL)
                {
                        if (!geom_found && typoid == postgis_oid(GEOMETRYOID))
                        {
                                ctx->geom_index = i;
                                geom_found = true;
                                continue;
                        }
                }
                else
                {
                        if (!geom_found && strcmp(tkey, ctx->geom_name) == 0)
                        {
                                ctx->geom_index = i;
                                geom_found = true;
                                continue;
                        }
                }
 
                ctx->column_cache.column_keys_index[i] = add_key(ctx, pstrdup(tkey));
        }
 
        if (!geom_found)
                elog(ERROR, "parse_column_keys: no geometry column found");
}
 
static void encode_keys(mvt_agg_context *ctx)
{
        struct mvt_kv_key *kv;
        size_t n_keys = ctx->keys_hash_i;
        char **keys = palloc(n_keys * sizeof(*keys));
        for (kv = ctx->keys_hash; kv != NULL; kv=kv->hh.next)
                keys[kv->id] = kv->name;
        ctx->layer->n_keys = n_keys;
        ctx->layer->keys = keys;
 
        HASH_CLEAR(hh, ctx->keys_hash);
}
 
static VectorTile__Tile__Value *create_value()
{
        VectorTile__Tile__Value *value = palloc(sizeof(*value));
        vector_tile__tile__value__init(value);
        return value;
}
 
#define MVT_CREATE_VALUES(kvtype, hash, hasfield, valuefield) \
{ \
        POSTGIS_DEBUG(2, "MVT_CREATE_VALUES called"); \
        { \
                struct kvtype *kv; \
                for (kv = ctx->hash; kv != NULL; kv=kv->hh.next) \
                { \
                        VectorTile__Tile__Value *value = create_value(); \
                        value->hasfield = 1; \
                        value->valuefield = kv->valuefield; \
                        values[kv->id] = value; \
                } \
        } \
}
 
static void encode_values(mvt_agg_context *ctx)
{
        VectorTile__Tile__Value **values;
        struct mvt_kv_string_value *kv;
 
        POSTGIS_DEBUG(2, "encode_values called");
 
        values = palloc(ctx->values_hash_i * sizeof(*values));
        for (kv = ctx->string_values_hash; kv != NULL; kv=kv->hh.next)
        {
                VectorTile__Tile__Value *value = create_value();
                value->string_value = kv->string_value;
                values[kv->id] = value;
        }
        MVT_CREATE_VALUES(mvt_kv_float_value,
                float_values_hash, has_float_value, float_value);
        MVT_CREATE_VALUES(mvt_kv_double_value,
                double_values_hash, has_double_value, double_value);
        MVT_CREATE_VALUES(mvt_kv_uint_value,
                uint_values_hash, has_uint_value, uint_value);
        MVT_CREATE_VALUES(mvt_kv_sint_value,
                sint_values_hash, has_sint_value, sint_value);
        MVT_CREATE_VALUES(mvt_kv_bool_value,
                bool_values_hash, has_bool_value, bool_value);
 
        POSTGIS_DEBUGF(3, "encode_values n_values: %d", ctx->values_hash_i);
        ctx->layer->n_values = ctx->values_hash_i;
        ctx->layer->values = values;
 
        HASH_CLEAR(hh, ctx->string_values_hash);
        HASH_CLEAR(hh, ctx->float_values_hash);
        HASH_CLEAR(hh, ctx->double_values_hash);
        HASH_CLEAR(hh, ctx->uint_values_hash);
        HASH_CLEAR(hh, ctx->sint_values_hash);
        HASH_CLEAR(hh, ctx->bool_values_hash);
 
        pfree(ctx->column_cache.column_keys_index);
        pfree(ctx->column_cache.column_oid);
        pfree(ctx->column_cache.values);
        pfree(ctx->column_cache.nulls);
        ReleaseTupleDesc(ctx->column_cache.tupdesc);
        memset(&ctx->column_cache, 0, sizeof(ctx->column_cache));
 
}
 
#define MVT_PARSE_VALUE(value, kvtype, hash, valuefield, size) \
{ \
        POSTGIS_DEBUG(2, "MVT_PARSE_VALUE called"); \
        { \
                struct kvtype *kv; \
                HASH_FIND(hh, ctx->hash, &value, size, kv); \
                if (!kv) \
                { \
                        POSTGIS_DEBUG(4, "MVT_PARSE_VALUE value not found"); \
                        kv = palloc(sizeof(*kv)); \
                        POSTGIS_DEBUGF(4, "MVT_PARSE_VALUE new hash key: %d", \
                                ctx->values_hash_i); \
                        kv->id = ctx->values_hash_i++; \
                        kv->valuefield = value; \
                        HASH_ADD(hh, ctx->hash, valuefield, size, kv); \
                } \
                tags[ctx->row_columns*2] = k; \
                tags[ctx->row_columns*2+1] = kv->id; \
        } \
}
 
#define MVT_PARSE_INT_VALUE(value) \
{ \
        if (value >= 0) \
        { \
                uint64_t cvalue = value; \
                MVT_PARSE_VALUE(cvalue, mvt_kv_uint_value, \
                                uint_values_hash, uint_value, \
                                sizeof(uint64_t)) \
        } \
        else \
        { \
                int64_t cvalue = value; \
                MVT_PARSE_VALUE(cvalue, mvt_kv_sint_value, \
                                sint_values_hash, sint_value, \
                                sizeof(int64_t)) \
        } \
}
 
#define MVT_PARSE_DATUM(type, kvtype, hash, valuefield, datumfunc, size) \
{ \
        type value = datumfunc(datum); \
        MVT_PARSE_VALUE(value, kvtype, hash, valuefield, size); \
}
 
#define MVT_PARSE_INT_DATUM(type, datumfunc) \
{ \
        type value = datumfunc(datum); \
        MVT_PARSE_INT_VALUE(value); \
}
 
static void add_value_as_string_with_size(mvt_agg_context *ctx,
        char *value, size_t size, uint32_t *tags, uint32_t k)
{
        struct mvt_kv_string_value *kv;
        POSTGIS_DEBUG(2, "add_value_as_string called");
        HASH_FIND(hh, ctx->string_values_hash, value, size, kv);
        if (!kv)
        {
                POSTGIS_DEBUG(4, "add_value_as_string value not found");
                kv = palloc(sizeof(*kv));
                POSTGIS_DEBUGF(4, "add_value_as_string new hash key: %d",
                        ctx->values_hash_i);
                kv->id = ctx->values_hash_i++;
                kv->string_value = value;
                HASH_ADD_KEYPTR(hh, ctx->string_values_hash, kv->string_value,
                        size, kv);
        }
        tags[ctx->row_columns*2] = k;
        tags[ctx->row_columns*2+1] = kv->id;
}
 
static void add_value_as_string(mvt_agg_context *ctx,
        char *value, uint32_t *tags, uint32_t k)
{
        return add_value_as_string_with_size(ctx, value, strlen(value), tags, k);
}
 
static void parse_datum_as_string(mvt_agg_context *ctx, Oid typoid,
        Datum datum, uint32_t *tags, uint32_t k)
{
        Oid foutoid;
        bool typisvarlena;
        char *value;
        POSTGIS_DEBUG(2, "parse_value_as_string called");
        getTypeOutputInfo(typoid, &foutoid, &typisvarlena);
        value = OidOutputFunctionCall(foutoid, datum);
        POSTGIS_DEBUGF(4, "parse_value_as_string value: %s", value);
        add_value_as_string(ctx, value, tags, k);
}
 
#if POSTGIS_PGSQL_VERSION >= 94
static uint32_t *parse_jsonb(mvt_agg_context *ctx, Jsonb *jb,
        uint32_t *tags)
{
        JsonbIterator *it;
        JsonbValue v;
        bool skipNested = false;
        JsonbIteratorToken r;
        uint32_t k;
 
        if (!JB_ROOT_IS_OBJECT(jb))
                return tags;
 
        it = JsonbIteratorInit(&jb->root);
 
        while ((r = JsonbIteratorNext(&it, &v, skipNested)) != WJB_DONE)
        {
                skipNested = true;
 
                if (r == WJB_KEY && v.type != jbvNull)
                {
 
                        k = get_key_index_with_size(ctx, v.val.string.val, v.val.string.len);
                        if (k == UINT32_MAX)
                        {
                                char *key;
                                uint32_t newSize = ctx->keys_hash_i + 1;
 
                                key = palloc(v.val.string.len + 1);
                                memcpy(key, v.val.string.val, v.val.string.len);
                                key[v.val.string.len] = '\0';
 
                                tags = repalloc(tags, newSize * 2 * sizeof(*tags));
                                k = add_key(ctx, key);
                        }
 
                        r = JsonbIteratorNext(&it, &v, skipNested);
 
                        if (v.type == jbvString)
                        {
                                char *value;
                                value = palloc(v.val.string.len + 1);
                                memcpy(value, v.val.string.val, v.val.string.len);
                                value[v.val.string.len] = '\0';
                                add_value_as_string(ctx, value, tags, k);
                                ctx->row_columns++;
                        }
                        else if (v.type == jbvBool)
                        {
                                MVT_PARSE_VALUE(v.val.boolean, mvt_kv_bool_value,
                                        bool_values_hash, bool_value, sizeof(protobuf_c_boolean));
                                ctx->row_columns++;
                        }
                        else if (v.type == jbvNumeric)
                        {
                                char *str;
                                double d;
                                long l;
                                str = DatumGetCString(DirectFunctionCall1(numeric_out,
                                        PointerGetDatum(v.val.numeric)));
                                d = strtod(str, NULL);
                                l = strtol(str, NULL, 10);
                                if (FP_NEQUALS(d, (double)l))
                                {
                                        MVT_PARSE_VALUE(d, mvt_kv_double_value, double_values_hash,
                                                double_value, sizeof(double));
                                }
                                else
                                {
                                        MVT_PARSE_INT_VALUE(l);
                                }
                                ctx->row_columns++;
                        }
                }
        }
 
        return tags;
}
#endif
 
static void parse_values(mvt_agg_context *ctx)
{
        uint32_t n_keys = ctx->keys_hash_i;
        uint32_t *tags = palloc(n_keys * 2 * sizeof(*tags));
        uint32_t i;
        mvt_column_cache cc = ctx->column_cache;
        uint32_t natts = (uint32_t) cc.tupdesc->natts;
 
        HeapTupleData tuple;
 
        POSTGIS_DEBUG(2, "parse_values called");
        ctx->row_columns = 0;
 
        /* Build a temporary HeapTuple control structure */
        tuple.t_len = HeapTupleHeaderGetDatumLength(ctx->row);
        ItemPointerSetInvalid(&(tuple.t_self));
        tuple.t_tableOid = InvalidOid;
        tuple.t_data = ctx->row;
 
        /* We use heap_deform_tuple as it costs only O(N) vs O(N^2) of GetAttributeByNum */
        heap_deform_tuple(&tuple, cc.tupdesc, cc.values, cc.nulls);
 
        POSTGIS_DEBUGF(3, "parse_values natts: %d", natts);
 
        for (i = 0; i < natts; i++)
        {
                char *key;
                Oid typoid;
                uint32_t k;
                Datum datum = cc.values[i];
 
                if (i == ctx->geom_index)
                        continue;
 
                if (cc.nulls[i])
                {
                        POSTGIS_DEBUG(3, "parse_values isnull detected");
                        continue;
                }
 
#if POSTGIS_PGSQL_VERSION < 110
                key = cc.tupdesc->attrs[i]->attname.data;
#else
                key = cc.tupdesc->attrs[i].attname.data;
#endif
                k = cc.column_keys_index[i];
                typoid = cc.column_oid[i];
 
#if POSTGIS_PGSQL_VERSION >= 94
                if (k == UINT32_MAX && typoid != JSONBOID)
                        elog(ERROR, "parse_values: unexpectedly could not find parsed key name '%s'", key);
                if (typoid == JSONBOID)
                {
                        tags = parse_jsonb(ctx, DatumGetJsonbP(datum), tags);
                        continue;
                }
#else
                if (k == UINT32_MAX)
                        elog(ERROR, "parse_values: unexpectedly could not find parsed key name '%s'", key);
#endif
 
                switch (typoid)
                {
                case BOOLOID:
                        MVT_PARSE_DATUM(protobuf_c_boolean, mvt_kv_bool_value,
                                bool_values_hash, bool_value,
                                DatumGetBool, sizeof(protobuf_c_boolean));
                        break;
                case INT2OID:
                        MVT_PARSE_INT_DATUM(int16_t, DatumGetInt16);
                        break;
                case INT4OID:
                        MVT_PARSE_INT_DATUM(int32_t, DatumGetInt32);
                        break;
                case INT8OID:
                        MVT_PARSE_INT_DATUM(int64_t, DatumGetInt64);
                        break;
                case FLOAT4OID:
                        MVT_PARSE_DATUM(float, mvt_kv_float_value,
                                float_values_hash, float_value,
                                DatumGetFloat4, sizeof(float));
                        break;
                case FLOAT8OID:
                        MVT_PARSE_DATUM(double, mvt_kv_double_value,
                                double_values_hash, double_value,
                                DatumGetFloat8, sizeof(double));
                        break;
                default:
                        parse_datum_as_string(ctx, typoid, datum, tags, k);
                        break;
                }
                ctx->row_columns++;
        }
 
 
        ctx->feature->n_tags = ctx->row_columns * 2;
        ctx->feature->tags = tags;
 
        POSTGIS_DEBUGF(3, "parse_values n_tags %zd", ctx->feature->n_tags);
}
 
/* For a given geometry, look for the highest dimensional basic type, that is,
 * point, line or polygon */
static uint8
lwgeom_get_basic_type(LWGEOM *geom)
{
        switch(geom->type)
        {
        case POINTTYPE:
        case LINETYPE:
        case POLYGONTYPE:
                return geom->type;
        case MULTIPOINTTYPE:
        case MULTILINETYPE:
        case MULTIPOLYGONTYPE:
                return geom->type - 3; /* Based on LWTYPE positions */
        case COLLECTIONTYPE:
        {
                uint32_t i;
                uint8 type = 0;
                LWCOLLECTION *g = (LWCOLLECTION*)geom;
                for (i = 0; i < g->ngeoms; i++)
                {
                        LWGEOM *sg = g->geoms[i];
                        type = Max(type, lwgeom_get_basic_type(sg));
                }
                return type;
        }
        default:
                elog(ERROR, "%s: Invalid type (%d)", __func__, geom->type);
        }
}
 
 
static inline LWGEOM *
lwgeom_to_basic_type(LWGEOM *geom, uint8 original_type)
{
        LWGEOM *geom_out = geom;
        if (lwgeom_get_type(geom) == COLLECTIONTYPE)
        {
                LWCOLLECTION *g = (LWCOLLECTION*)geom;
                geom_out = (LWGEOM *)lwcollection_extract(g, original_type);
        }
 
        /* If a collection only contains 1 geometry return than instead */
        if (lwgeom_is_collection(geom_out))
        {
                LWCOLLECTION *g = (LWCOLLECTION *)geom_out;
                if (g->ngeoms == 1)
                {
                        geom_out = g->geoms[0];
                }
        }
 
        geom_out->srid = geom->srid;
        return geom_out;
}
 
/* Clips a geometry using lwgeom_clip_by_rect. Might return NULL */
static LWGEOM *
mvt_unsafe_clip_by_box(LWGEOM *lwg_in, GBOX *clip_box)
{
        LWGEOM *geom_clipped;
        GBOX geom_box;
 
        gbox_init(&geom_box);
        FLAGS_SET_GEODETIC(geom_box.flags, 0);
        lwgeom_calculate_gbox(lwg_in, &geom_box);
 
        if (!gbox_overlaps_2d(&geom_box, clip_box))
        {
                POSTGIS_DEBUG(3, "mvt_geom: geometry outside clip box");
                return NULL;
        }
 
        if (gbox_contains_2d(clip_box, &geom_box))
        {
                POSTGIS_DEBUG(3, "mvt_geom: geometry contained fully inside the box");
                return lwg_in;
        }
 
        geom_clipped = lwgeom_clip_by_rect(lwg_in, clip_box->xmin, clip_box->ymin, clip_box->xmax, clip_box->ymax);
        if (!geom_clipped || lwgeom_is_empty(geom_clipped))
                return NULL;
        return geom_clipped;
}
 
static LWGEOM *
mvt_safe_clip_polygon_by_box(LWGEOM *lwg_in, GBOX *clip_box)
{
        LWGEOM *geom_clipped, *envelope;
        GBOX geom_box;
        GEOSGeometry *geos_input, *geos_box, *geos_result;
 
        gbox_init(&geom_box);
        FLAGS_SET_GEODETIC(geom_box.flags, 0);
        lwgeom_calculate_gbox(lwg_in, &geom_box);
 
        if (!gbox_overlaps_2d(&geom_box, clip_box))
        {
                POSTGIS_DEBUG(3, "mvt_geom: geometry outside clip box");
                return NULL;
        }
 
        if (gbox_contains_2d(clip_box, &geom_box))
        {
                POSTGIS_DEBUG(3, "mvt_geom: geometry contained fully inside the box");
                return lwg_in;
        }
 
        initGEOS(lwnotice, lwgeom_geos_error);
        if (!(geos_input = LWGEOM2GEOS(lwg_in, 1)))
                return NULL;
 
        envelope = (LWGEOM *)lwpoly_construct_envelope(
            lwg_in->srid, clip_box->xmin, clip_box->ymin, clip_box->xmax, clip_box->ymax);
        geos_box = LWGEOM2GEOS(envelope, 1);
        lwgeom_free(envelope);
        if (!geos_box)
        {
                GEOSGeom_destroy(geos_input);
                return NULL;
        }
 
        geos_result = GEOSIntersection(geos_input, geos_box);
        if (!geos_result)
        {
                POSTGIS_DEBUG(3, "mvt_geom: no geometry after intersection. Retrying after validation");
                GEOSGeom_destroy(geos_input);
                lwg_in = lwgeom_make_valid(lwg_in);
                if (!(geos_input = LWGEOM2GEOS(lwg_in, 1)))
                {
                        GEOSGeom_destroy(geos_box);
                        return NULL;
                }
                geos_result = GEOSIntersection(geos_input, geos_box);
                if (!geos_result)
                {
                        GEOSGeom_destroy(geos_box);
                        GEOSGeom_destroy(geos_input);
                        return NULL;
                }
        }
 
        GEOSSetSRID(geos_result, lwg_in->srid);
        geom_clipped = GEOS2LWGEOM(geos_result, 0);
 
        GEOSGeom_destroy(geos_box);
        GEOSGeom_destroy(geos_input);
        GEOSGeom_destroy(geos_result);
 
        if (!geom_clipped || lwgeom_is_empty(geom_clipped))
        {
                POSTGIS_DEBUG(3, "mvt_geom: no geometry after clipping");
                return NULL;
        }
 
        return geom_clipped;
}
 
static LWGEOM *
mvt_iterate_clip_by_box_geos(LWGEOM *lwgeom, GBOX *clip_gbox, uint8_t basic_type)
{
        if (basic_type != POLYGONTYPE)
        {
                return mvt_unsafe_clip_by_box(lwgeom, clip_gbox);
        }
 
        if (lwgeom->type != MULTIPOLYGONTYPE || ((LWMPOLY *)lwgeom)->ngeoms == 1)
        {
                return mvt_safe_clip_polygon_by_box(lwgeom, clip_gbox);
        }
        else
        {
                GBOX geom_box;
                uint32_t i;
                LWCOLLECTION *lwmg;
                LWCOLLECTION *res;
 
                gbox_init(&geom_box);
                FLAGS_SET_GEODETIC(geom_box.flags, 0);
                lwgeom_calculate_gbox(lwgeom, &geom_box);
 
                lwmg = ((LWCOLLECTION *)lwgeom);
                res = lwcollection_construct_empty(
                    MULTIPOLYGONTYPE, lwgeom->srid, FLAGS_GET_Z(lwgeom->flags), FLAGS_GET_M(lwgeom->flags));
                for (i = 0; i < lwmg->ngeoms; i++)
                {
                        LWGEOM *clipped = mvt_safe_clip_polygon_by_box(lwcollection_getsubgeom(lwmg, i), clip_gbox);
                        if (clipped)
                        {
                                clipped = lwgeom_to_basic_type(clipped, POLYGONTYPE);
                                if (!lwgeom_is_empty(clipped) &&
                                    (clipped->type == POLYGONTYPE || clipped->type == MULTIPOLYGONTYPE))
                                {
                                        if (!lwgeom_is_collection(clipped))
                                        {
                                                lwcollection_add_lwgeom(res, clipped);
                                        }
                                        else
                                        {
                                                uint32_t j;
                                                for (j = 0; j < ((LWCOLLECTION *)clipped)->ngeoms; j++)
                                                        lwcollection_add_lwgeom(
                                                            res, lwcollection_getsubgeom((LWCOLLECTION *)clipped, j));
                                        }
                                }
                        }
                }
                return lwcollection_as_lwgeom(res);
        }
}
 
static LWGEOM *
mvt_grid_and_validate_geos(LWGEOM *ng, uint8_t basic_type)
{
        gridspec grid = {0, 0, 0, 0, 1, 1, 0, 0};
        ng = lwgeom_to_basic_type(ng, basic_type);
 
        if (basic_type != POLYGONTYPE)
        {
                /* Make sure there is no pending float values (clipping can do that) */
                lwgeom_grid_in_place(ng, &grid);
        }
        else
        {
                /* For polygons we have to both snap to the integer grid and force validation.
                 * The problem with this procedure is that snapping to the grid can create
                 * an invalid geometry and making it valid can create float values; so
                 * we iterate several times (up to 3) to generate a valid geom with int coordinates
                 */
                GEOSGeometry *geo;
                uint32_t iterations = 0;
                static const uint32_t max_iterations = 3;
                bool valid = false;
 
                /* Grid to int */
                lwgeom_grid_in_place(ng, &grid);
 
                initGEOS(lwgeom_geos_error, lwgeom_geos_error);
                geo = LWGEOM2GEOS(ng, 0);
                if (!geo)
                        return NULL;
                valid = GEOSisValid(geo) == 1;
 
                while (!valid && iterations < max_iterations)
                {
#if POSTGIS_GEOS_VERSION < 38
                        GEOSGeometry *geo_valid = LWGEOM_GEOS_makeValid(geo);
#else
                        GEOSGeometry *geo_valid = GEOSMakeValid(geo);
#endif
                        GEOSGeom_destroy(geo);
                        if (!geo_valid)
                                return NULL;
 
                        ng = GEOS2LWGEOM(geo_valid, 0);
                        GEOSGeom_destroy(geo_valid);
                        if (!ng)
                                return NULL;
 
                        lwgeom_grid_in_place(ng, &grid);
                        ng = lwgeom_to_basic_type(ng, basic_type);
                        geo = LWGEOM2GEOS(ng, 0);
                        valid = GEOSisValid(geo) == 1;
                        iterations++;
                }
                GEOSGeom_destroy(geo);
 
                if (!valid)
                {
                        POSTGIS_DEBUG(1, "mvt_geom: Could not transform into a valid MVT geometry");
                        return NULL;
                }
 
                /* In image coordinates CW actually comes out a CCW, so we reverse */
                lwgeom_force_clockwise(ng);
                lwgeom_reverse_in_place(ng);
        }
        return ng;
}
 
/* Clips and validates a geometry for MVT using GEOS
 * Might return NULL
 */
static LWGEOM *
mvt_clip_and_validate_geos(LWGEOM *lwgeom, uint8_t basic_type, uint32_t extent, uint32_t buffer, bool clip_geom)
{
        LWGEOM *ng = lwgeom;
 
        if (clip_geom)
        {
                GBOX bgbox;
                gbox_init(&bgbox);
                bgbox.xmax = bgbox.ymax = (double)extent + (double)buffer;
                bgbox.xmin = bgbox.ymin = -(double)buffer;
                FLAGS_SET_GEODETIC(bgbox.flags, 0);
 
                ng = mvt_iterate_clip_by_box_geos(lwgeom, &bgbox, basic_type);
                if (!ng || lwgeom_is_empty(ng))
                {
                        POSTGIS_DEBUG(3, "mvt_geom: no geometry after clip");
                        return NULL;
                }
        }
 
        ng = mvt_grid_and_validate_geos(ng, basic_type);
 
        /* Make sure we return the expected type */
        if (!ng || basic_type != lwgeom_get_basic_type(ng))
        {
                /* Drop type changes to play nice with MVT renderers */
                POSTGIS_DEBUG(1, "mvt_geom: Dropping geometry after type change");
                return NULL;
        }
 
        return ng;
}
 
LWGEOM *mvt_geom(LWGEOM *lwgeom, const GBOX *gbox, uint32_t extent, uint32_t buffer,
        bool clip_geom)
{
        AFFINE affine = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
        gridspec grid = {0, 0, 0, 0, 1, 1, 0, 0};
        double width = gbox->xmax - gbox->xmin;
        double height = gbox->ymax - gbox->ymin;
        double resx, resy, res, fx, fy;
        const uint8_t basic_type = lwgeom_get_basic_type(lwgeom);
        int preserve_collapsed = LW_FALSE;
        POSTGIS_DEBUG(2, "mvt_geom called");
 
        /* Simplify it as soon as possible */
        lwgeom = lwgeom_to_basic_type(lwgeom, basic_type);
 
        /* Short circuit out on EMPTY */
        if (lwgeom_is_empty(lwgeom))
                return NULL;
 
        if (width == 0 || height == 0)
                elog(ERROR, "mvt_geom: bounds width or height cannot be 0");
 
        if (extent == 0)
                elog(ERROR, "mvt_geom: extent cannot be 0");
 
        resx = width / extent;
        resy = height / extent;
        res = (resx < resy ? resx : resy)/2;
        fx = extent / width;
        fy = -(extent / height);
 
        /* Remove all non-essential points (under the output resolution) */
        lwgeom_remove_repeated_points_in_place(lwgeom, res);
        lwgeom_simplify_in_place(lwgeom, res, preserve_collapsed);
 
        /* If geometry has disappeared, you're done */
        if (lwgeom_is_empty(lwgeom))
                return NULL;
 
        /* transform to tile coordinate space */
        affine.afac = fx;
        affine.efac = fy;
        affine.ifac = 1;
        affine.xoff = -gbox->xmin * fx;
        affine.yoff = -gbox->ymax * fy;
        lwgeom_affine(lwgeom, &affine);
 
        /* snap to integer precision, removing duplicate points */
        lwgeom_grid_in_place(lwgeom, &grid);
 
        if (lwgeom == NULL || lwgeom_is_empty(lwgeom))
                return NULL;
 
        lwgeom = mvt_clip_and_validate_geos(lwgeom, basic_type, extent, buffer, clip_geom);
        if (lwgeom == NULL || lwgeom_is_empty(lwgeom))
                return NULL;
 
        return lwgeom;
}
 
void mvt_agg_init_context(mvt_agg_context *ctx)
{
        VectorTile__Tile__Layer *layer;
 
        POSTGIS_DEBUG(2, "mvt_agg_init_context called");
 
        if (ctx->extent == 0)
                elog(ERROR, "mvt_agg_init_context: extent cannot be 0");
 
        ctx->tile = NULL;
        ctx->features_capacity = FEATURES_CAPACITY_INITIAL;
        ctx->keys_hash = NULL;
        ctx->string_values_hash = NULL;
        ctx->float_values_hash = NULL;
        ctx->double_values_hash = NULL;
        ctx->uint_values_hash = NULL;
        ctx->sint_values_hash = NULL;
        ctx->bool_values_hash = NULL;
        ctx->values_hash_i = 0;
        ctx->keys_hash_i = 0;
        ctx->geom_index = UINT32_MAX;
 
        memset(&ctx->column_cache, 0, sizeof(ctx->column_cache));
 
        layer = palloc(sizeof(*layer));
        vector_tile__tile__layer__init(layer);
        layer->version = 2;
        layer->name = ctx->name;
        layer->has_extent = 1;
        layer->extent = ctx->extent;
        layer->features = palloc (ctx->features_capacity *
                sizeof(*layer->features));
 
        ctx->layer = layer;
}
 
void mvt_agg_transfn(mvt_agg_context *ctx)
{
        bool isnull = false;
        Datum datum;
        GSERIALIZED *gs;
        LWGEOM *lwgeom;
        VectorTile__Tile__Feature *feature;
        VectorTile__Tile__Layer *layer = ctx->layer;
/*      VectorTile__Tile__Feature **features = layer->features; */
        POSTGIS_DEBUG(2, "mvt_agg_transfn called");
 
        if (layer->n_features >= ctx->features_capacity)
        {
                size_t new_capacity = ctx->features_capacity * 2;
                layer->features = repalloc(layer->features, new_capacity *
                        sizeof(*layer->features));
                ctx->features_capacity = new_capacity;
                POSTGIS_DEBUGF(3, "mvt_agg_transfn new_capacity: %zd", new_capacity);
        }
 
        if (ctx->geom_index == UINT32_MAX)
                parse_column_keys(ctx);
 
        datum = GetAttributeByNum(ctx->row, ctx->geom_index + 1, &isnull);
        POSTGIS_DEBUGF(3, "mvt_agg_transfn ctx->geom_index: %d", ctx->geom_index);
        POSTGIS_DEBUGF(3, "mvt_agg_transfn isnull: %u", isnull);
        POSTGIS_DEBUGF(3, "mvt_agg_transfn datum: %lu", datum);
        if (isnull) /* Skip rows that have null geometry */
        {
                POSTGIS_DEBUG(3, "mvt_agg_transfn got null geom");
                return;
        }
 
        feature = palloc(sizeof(*feature));
        vector_tile__tile__feature__init(feature);
 
        ctx->feature = feature;
 
        gs = (GSERIALIZED *) PG_DETOAST_DATUM(datum);
        lwgeom = lwgeom_from_gserialized(gs);
 
        POSTGIS_DEBUGF(3, "mvt_agg_transfn encoded feature count: %zd", layer->n_features);
        layer->features[layer->n_features++] = feature;
 
        encode_geometry(ctx, lwgeom);
        lwgeom_free(lwgeom);
        // TODO: free detoasted datum?
        parse_values(ctx);
}
 
static VectorTile__Tile * mvt_ctx_to_tile(mvt_agg_context *ctx)
{
        int n_layers = 1;
        VectorTile__Tile *tile;
        encode_keys(ctx);
        encode_values(ctx);
 
        tile = palloc(sizeof(VectorTile__Tile));
        vector_tile__tile__init(tile);
        tile->layers = palloc(sizeof(VectorTile__Tile__Layer*) * n_layers);
        tile->layers[0] = ctx->layer;
        tile->n_layers = n_layers;
        return tile;
}
 
static bytea *mvt_ctx_to_bytea(mvt_agg_context *ctx)
{
        /* Fill out the file slot, if it's not already filled. */
        /* We should only have a filled slow when all the work of building */
        /* out the data is complete, so after a serialize/deserialize cycle */
        /* or after a context combine */
        size_t len;
        bytea *ba;
 
        if (!ctx->tile)
        {
                ctx->tile = mvt_ctx_to_tile(ctx);
        }
 
        /* Zero features => empty bytea output */
        if (ctx && ctx->layer && ctx->layer->n_features == 0)
        {
                bytea *ba = palloc(VARHDRSZ);
                SET_VARSIZE(ba, VARHDRSZ);
                return ba;
        }
 
        /* Serialize the Tile */
        len = VARHDRSZ + vector_tile__tile__get_packed_size(ctx->tile);
        ba = palloc(len);
        vector_tile__tile__pack(ctx->tile, (uint8_t*)VARDATA(ba));
        SET_VARSIZE(ba, len);
        return ba;
}
 
 
bytea * mvt_ctx_serialize(mvt_agg_context *ctx)
{
        return mvt_ctx_to_bytea(ctx);
}
 
static void * mvt_allocator(__attribute__((__unused__)) void *data, size_t size)
{
        return palloc(size);
}
 
static void mvt_deallocator(__attribute__((__unused__)) void *data, void *ptr)
{
        return pfree(ptr);
}
 
mvt_agg_context * mvt_ctx_deserialize(const bytea *ba)
{
        ProtobufCAllocator allocator =
        {
                mvt_allocator,
                mvt_deallocator,
                NULL
        };
 
        size_t len = VARSIZE(ba) - VARHDRSZ;
        VectorTile__Tile *tile = vector_tile__tile__unpack(&allocator, len, (uint8_t*)VARDATA(ba));
        mvt_agg_context *ctx = palloc(sizeof(mvt_agg_context));
        memset(ctx, 0, sizeof(mvt_agg_context));
        ctx->tile = tile;
        return ctx;
}
 
static VectorTile__Tile__Value *
tile_value_copy(const VectorTile__Tile__Value *value)
{
        VectorTile__Tile__Value *nvalue = palloc(sizeof(VectorTile__Tile__Value));
        memcpy(nvalue, value, sizeof(VectorTile__Tile__Value));
        if (value->string_value)
                nvalue->string_value = pstrdup(value->string_value);
        return nvalue;
}
 
static VectorTile__Tile__Feature *
tile_feature_copy(const VectorTile__Tile__Feature *feature, int key_offset, int value_offset)
{
        uint32_t i;
        VectorTile__Tile__Feature *nfeature;
 
        /* Null in => Null out */
        if (!feature) return NULL;
 
        /* Init object */
        nfeature = palloc(sizeof(VectorTile__Tile__Feature));
        vector_tile__tile__feature__init(nfeature);
 
        /* Copy settings straight over */
        nfeature->has_id = feature->has_id;
        nfeature->id = feature->id;
        nfeature->has_type = feature->has_type;
        nfeature->type = feature->type;
 
        /* Copy tags over, offsetting indexes so they match the dictionaries */
        /* at the Tile_Layer level */
        if (feature->n_tags > 0)
        {
                nfeature->n_tags = feature->n_tags;
                nfeature->tags = palloc(sizeof(uint32_t)*feature->n_tags);
                for (i = 0; i < feature->n_tags/2; i++)
                {
                        nfeature->tags[2*i] = feature->tags[2*i] + key_offset;
                        nfeature->tags[2*i+1] = feature->tags[2*i+1] + value_offset;
                }
        }
 
        /* Copy the raw geometry data over literally */
        if (feature->n_geometry > 0)
        {
                nfeature->n_geometry = feature->n_geometry;
                nfeature->geometry = palloc(sizeof(uint32_t)*feature->n_geometry);
                memcpy(nfeature->geometry, feature->geometry, sizeof(uint32_t)*feature->n_geometry);
        }
 
        /* Done */
        return nfeature;
}
 
static VectorTile__Tile__Layer *
vectortile_layer_combine(const VectorTile__Tile__Layer *layer1, const VectorTile__Tile__Layer *layer2)
{
        uint32_t i, j;
        int key2_offset, value2_offset;
        VectorTile__Tile__Layer *layer = palloc(sizeof(VectorTile__Tile__Layer));
        vector_tile__tile__layer__init(layer);
 
        /* Take globals from layer1 */
        layer->version = layer1->version;
        layer->name = pstrdup(layer1->name);
        layer->has_extent = layer1->has_extent;
        layer->extent = layer1->extent;
 
        /* Copy keys into new layer */
        j = 0;
        layer->n_keys = layer1->n_keys + layer2->n_keys;
        layer->keys = layer->n_keys ? palloc(layer->n_keys * sizeof(void*)) : NULL;
        for (i = 0; i < layer1->n_keys; i++)
                layer->keys[j++] = pstrdup(layer1->keys[i]);
        key2_offset = j;
        for (i = 0; i < layer2->n_keys; i++)
                layer->keys[j++] = pstrdup(layer2->keys[i]);
 
        /* Copy values into new layer */
        /* TODO, apply hash logic here too, so that merged tiles */
        /* retain unique value maps */
        layer->n_values = layer1->n_values + layer2->n_values;
        layer->values = layer->n_values ? palloc(layer->n_values * sizeof(void*)) : NULL;
        j = 0;
        for (i = 0; i < layer1->n_values; i++)
                layer->values[j++] = tile_value_copy(layer1->values[i]);
        value2_offset = j;
        for (i = 0; i < layer2->n_values; i++)
                layer->values[j++] = tile_value_copy(layer2->values[i]);
 
 
        layer->n_features = layer1->n_features + layer2->n_features;
        layer->features = layer->n_features ? palloc(layer->n_features * sizeof(void*)) : NULL;
        j = 0;
        for (i = 0; i < layer1->n_features; i++)
                layer->features[j++] = tile_feature_copy(layer1->features[i], 0, 0);
        for (i = 0; i < layer2->n_features; i++)
                layer->features[j++] = tile_feature_copy(layer2->features[i], key2_offset, value2_offset);
 
        return layer;
}
 
 
static VectorTile__Tile *
vectortile_tile_combine(VectorTile__Tile *tile1, VectorTile__Tile *tile2)
{
        uint32_t i, j;
        VectorTile__Tile *tile;
 
        /* Hopelessly messing up memory ownership here */
        if (tile1->n_layers == 0 && tile2->n_layers == 0)
                return tile1;
        else if (tile1->n_layers == 0)
                return tile2;
        else if (tile2->n_layers == 0)
                return tile1;
 
        tile = palloc(sizeof(VectorTile__Tile));
        vector_tile__tile__init(tile);
        tile->layers = palloc(sizeof(void*));
        tile->n_layers = 0;
 
        /* Merge all matching layers in the files (basically always only one) */
        for (i = 0; i < tile1->n_layers; i++)
        {
                for (j = 0; j < tile2->n_layers; j++)
                {
                        VectorTile__Tile__Layer *l1 = tile1->layers[i];
                        VectorTile__Tile__Layer *l2 = tile2->layers[j];
                        if (strcmp(l1->name, l2->name)==0)
                        {
                                VectorTile__Tile__Layer *layer = vectortile_layer_combine(l1, l2);
                                if (!layer)
                                        continue;
                                tile->layers[tile->n_layers++] = layer;
                                /* Add a spare slot at the end of the array */
                                tile->layers = repalloc(tile->layers, (tile->n_layers+1) * sizeof(void*));
                        }
                }
        }
        return tile;
}
 
mvt_agg_context * mvt_ctx_combine(mvt_agg_context *ctx1, mvt_agg_context *ctx2)
{
        if (ctx1 || ctx2)
        {
                if (ctx1 && ! ctx2) return ctx1;
                if (ctx2 && ! ctx1) return ctx2;
                if (ctx1 && ctx2 && ctx1->tile && ctx2->tile)
                {
                        mvt_agg_context *ctxnew = palloc(sizeof(mvt_agg_context));
                        memset(ctxnew, 0, sizeof(mvt_agg_context));
                        ctxnew->tile = vectortile_tile_combine(ctx1->tile, ctx2->tile);
                        return ctxnew;
                }
                else
                {
                        elog(DEBUG2, "ctx1->tile = %p", ctx1->tile);
                        elog(DEBUG2, "ctx2->tile = %p", ctx2->tile);
                        elog(ERROR, "%s: unable to combine contexts where tile attribute is null", __func__);
                        return NULL;
                }
        }
        else
        {
                return NULL;
        }
}
 
bytea *mvt_agg_finalfn(mvt_agg_context *ctx)
{
        return mvt_ctx_to_bytea(ctx);
}
 
 
#endif