diff --git a/package.json b/package.json
index 66d5af2..ce6206b 100644
--- a/package.json
+++ b/package.json
@@ -21,6 +21,7 @@
     "eslint-plugin-react-hooks": "^2.3.0",
     "leaflet": "^1.6.0",
     "lodash": "^4.17.15",
+    "object-hash": "^2.0.1",
     "prop-types": "^15.6.0",
     "react": "^16.12.0",
     "react-dom": "^16.12.0",
diff --git a/src/database.js b/src/database.js
index a9a1135..340d3fc 100644
--- a/src/database.js
+++ b/src/database.js
@@ -1,17 +1,19 @@
-import React, { useEffect, useState } from 'react';
+import React, { useEffect, useState, useContext } from 'react';
 import NodeEnvironment from 'jest-environment-node';
 
+import { add_polygon_to_store, get_polygon_from_store } from './polygons.js';
+
 export async function sqljs_async_queries(sqljs_object, queries) {
   //var t0 = performance.now();
   for (let i = 0; i < (queries.length - 1); i++) {
-    console.log("Query: ", queries[i]);
+    //console.log("Query: ", queries[i]);
     try {
       sqljs_object.exec(queries[i]);
     } catch (e) {
       throw e;
     }
   }
-  console.log("Query: ", queries[queries.length - 1]);
+  //console.log("Query: ", queries[queries.length - 1]);
   try {
     var r = sqljs_object.exec(queries[queries.length - 1]);
   } catch (e) {
@@ -47,13 +49,13 @@ export function regexp_match(string, regex) {
   return string.match(regex) != null;
 }
 
-export function is_in_geo_polygon(lat, long, polyid) {
-  return true;
+export function is_in_polygon(x, y, poly) {
+  return false;
 }
 
-export function add_custom_functions(db) {
-  db.create_function("REGEXP", regexp_match);
-  db.create_function("IS_IN_GEO_POLYGON", is_in_geo_polygon);
+export function is_in_geo_polygon_from_store(lat, long, polygon_hash) {
+  const poly = get_polygon_from_store(polygon_hash);
+  return is_in_polygon(lat, long, poly);
 }
 
 // Digikam stores its tree of tags as individual tags,
@@ -102,8 +104,6 @@ export async function add_full_tag_info(db) {
     db.exec(query);
   });
 
-  console.log(db.exec("PRAGMA table_info([Tags]);"));
-
   return db;
 }
 
@@ -116,7 +116,8 @@ export function ProvideDB(props) {
     fetch_sqljs_db_from_sqlite(db_url)
       .then(db => {
         add_full_tag_info(db).then((newdb) => {
-          add_custom_functions(newdb);
+          db.create_function("REGEXP", regexp_match);
+          db.create_function("IS_IN_GEO_POLYGON", is_in_geo_polygon_from_store);
           setError(false);
           setDb(newdb);
         })
@@ -129,9 +130,5 @@ export function ProvideDB(props) {
     db_error: error,
   };
 
-  if (db != null) {
-    console.log("Provided DB tags schema:", db.exec("PRAGMA table_info([Tags]);"));
-  }
-
   return children({ ...child_props });
 }
\ No newline at end of file
diff --git a/src/gridgallery.js b/src/gridgallery.js
index a03b360..01c80ec 100644
--- a/src/gridgallery.js
+++ b/src/gridgallery.js
@@ -3,6 +3,8 @@ import Gallery from 'react-grid-gallery';
 
 import { makeStyles } from '@material-ui/core/styles';
 
+// TODO: some nice options: ModuloBox, 
+
 const useStyles = makeStyles(theme => ({
     root: {
         width: "100%",
diff --git a/src/main.js b/src/main.js
index ccf78c3..10a1704 100644
--- a/src/main.js
+++ b/src/main.js
@@ -12,7 +12,6 @@ import { UserQuery, user_query_from_search_string, maybe_image_query, do_image_q
 import { Browser } from './browser.js';
 import { UserQueryWidget } from './userquerywidget.js';
 import { ResultsView } from './resultsview.js';
-import { PolygonStoreProvider } from './polygons.js';
 
 const useStyles = makeStyles(theme => ({
     root: {
@@ -126,18 +125,16 @@ export function LoadedMainPage(props) {
 
     return (
         <>
-            <PolygonStoreProvider>
-                <Box className={classes.root}>
-                    <Box className={classes.navigator}>
-                        <Box className={classes.margined}>{albums && <Browser albums={allAlbums} tags={allTags} onNewQuery={onNewQuery} />}</Box>
-                    </Box>
-                    <Box className={classes.searchandview}>
-                        <Box className={classes.margined}><SearchBar onSubmit={onSearch} /></Box>
-                        <Box className={classes.margined}><UserQueryWidget userQuery={gallery_user_query} onChange={onNewQuery} /></Box>
-                        <Box className={classes.margined}>{photos && <ResultsView photos={photos ? photos : []} albums={albums ? albums : []} tags={tags ? tags : []} />}</Box>
-                    </Box>
+            <Box className={classes.root}>
+                <Box className={classes.navigator}>
+                    <Box className={classes.margined}>{albums && <Browser albums={allAlbums} tags={allTags} onNewQuery={onNewQuery} />}</Box>
                 </Box>
-            </PolygonStoreProvider>
+                <Box className={classes.searchandview}>
+                    <Box className={classes.margined}><SearchBar onSubmit={onSearch} /></Box>
+                    <Box className={classes.margined}><UserQueryWidget userQuery={gallery_user_query} onChange={onNewQuery} /></Box>
+                    <Box className={classes.margined}>{photos && <ResultsView photos={photos ? photos : []} albums={albums ? albums : []} tags={tags ? tags : []} />}</Box>
+                </Box>
+            </Box>
         </>
     );
 }
diff --git a/src/map.js b/src/map.js
index 67e9b22..0874132 100644
--- a/src/map.js
+++ b/src/map.js
@@ -58,7 +58,7 @@ export function MapView(props) {
         fetch("http://nominatim.openstreetmap.org/search?polygon_geojson=1&polygon_threshold=0.001&format=json&limit=5&q=" + query)
             .then(res => res.json())
             .then(jsonres => {
-                console.log(jsonres);
+                //console.log("Nominatim result: ", jsonres);
                 if (Array.isArray(jsonres) && jsonres.length > 0) {
                     showNominatimResult(jsonres[0]);
                 }
diff --git a/src/polygons.js b/src/polygons.js
index 2462584..476433c 100644
--- a/src/polygons.js
+++ b/src/polygons.js
@@ -1,21 +1,22 @@
-import React, { createContext, useReducer } from 'react';
+var g_PolygonStore = {};
 
-const polygonStore = createContext({});
-const { Provider } = polygonStore;
+export function hash_polygon(polygon) {
+    var hash = require('object-hash');
+    return hash(polygon);
+}
 
-const PolygonStoreProvider = ({ children }) => {
-    const [state, dispatch] = useReducer((state, action) => {
-        switch (action.type) {
-            case 'add polygon':
-                const newstate = state;
-                newstate[action.payload.id] = action.payload.data;
-                return newstate;
-            default:
-                throw new Error();
-        };
-    }, {});
+export function add_polygon_to_store(polygon) {
+    var h = hash_polygon(polygon);
+    if(!(h in g_PolygonStore)) {
+        g_PolygonStore[h] = polygon;
+    }
 
-    return <Provider value={{ state, dispatch }}>{children}</Provider>;
-};
+    return h;
+}
 
-export { polygonStore, PolygonStoreProvider }
\ No newline at end of file
+export function get_polygon_from_store(polygon_hash) {
+    if(polygon_hash in g_PolygonStore) {
+        return g_PolygonStore[polygon_hash];
+    }
+    throw new Error("Requested non-existent polygon from store.");
+}
\ No newline at end of file
diff --git a/src/queries.js b/src/queries.js
index 70ec079..d0a8bd3 100644
--- a/src/queries.js
+++ b/src/queries.js
@@ -2,6 +2,7 @@
 import { create_photo, create_album, create_tag } from './media.js';
 import { sqljs_async_queries } from './database.js';
 import { format } from 'date-fns';
+import { add_polygon_to_store } from './polygons.js';
 
 export function escape_regex(s) {
     return s.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');
@@ -12,7 +13,7 @@ export function do_image_query(query, database, collection_path, collection_thum
         var queries = [];
         queries.push(query);
         sqljs_async_queries(database, queries).then(res => {
-            console.log("response: ", res);
+            //console.log("Query result: ", res);
             var photos = [];
             if (res && Array.isArray(res) && res.length > 0) {
                 var cols = res[0].columns;
@@ -61,7 +62,6 @@ export function do_tag_query(query, database) {
     return new Promise(function (resolve, reject) {
         var queries = [];
         queries.push(query);
-        console.log("Provided DB tags schema before query:", database.exec("PRAGMA table_info([Tags]);"));
         sqljs_async_queries(database, queries).then(res => {
             var tags = [];
             if (res && Array.isArray(res) && res.length > 0) {
@@ -136,7 +136,6 @@ export class NegationFilter extends ResultFilter {
 
     simplify() {
         var f = this.body.simplify();
-        console.log("NOT body:", f);
         if (f.is_true()) {
             return new ConstFilter(this.result_type, false);
         }
@@ -248,7 +247,6 @@ export class MatchingFilter extends ResultFilter {
                 + '(\/[^\/]+)*"))';
         }
 
-        console.log(this);
         throw new Error("Unsupported matching filter for SQL generation.");
     }
     simplify() { return this; }
@@ -306,10 +304,9 @@ export class LogicalOperatorFilter extends ResultFilter {
 export class LocationFilter extends ResultFilter {
     // The location filter always compares object locations (points)
     // to a location polygon and filters objects outside said polygon.
-    constructor(rtype, polygon, polygon_store_dispatch) {
+    constructor(rtype, polygon) {
         super(rtype);
         this.polygon = polygon;
-        this.polygon_store_dispatch = polygon_store_dispatch;
     }
 
     to_sql_where() {
@@ -319,13 +316,8 @@ export class LocationFilter extends ResultFilter {
         // by the custom comparison function invoked by SQL.js.
         // We need to store our polygon in said state and then return the query to guarantee that
         // it will have access to said polygon.
-        const _ = require('lodash');
-        const poly = {
-            id: _.uniqueId('polygon_'),
-            data: this.polygon
-        }
-        this.polygon_store_dispatch({ type: 'add polygon', payload: poly });
-        return 'IS_IN_GEO_POLYGON(ImagePositions.latitude, ImagePositions.longitude, "' + poly.id + '")';
+        const hash = add_polygon_to_store(this.polygon);
+        return 'IS_IN_GEO_POLYGON(ImagePositions.latitude, ImagePositions.longitude, "' + hash + '")';
     }
 
     simplify() { return this; }
diff --git a/src/userquerywidget.js b/src/userquerywidget.js
index 5303eef..5688206 100644
--- a/src/userquerywidget.js
+++ b/src/userquerywidget.js
@@ -24,8 +24,6 @@ import { format } from 'date-fns';
 
 import { makeStyles } from '@material-ui/core/styles';
 
-import { polygonStore } from './polygons.js';
-
 import {
     filter_is_const_false, ConstFilter, LogicalOperatorFilter, MatchingFilter,
     ResultTypeEnum, LogicalOperatorEnum, MatchTypeEnum, NegationFilter, TimeFilterTypeEnum,
@@ -239,8 +237,6 @@ export function EditFilterExpressionDialog(props) {
     const { onClose, startingFilter, open } = props;
     const [filter, setFilter] = React.useState(startingFilter);
 
-    const polygons_dispatch = useContext(polygonStore).dispatch;
-
     const FilterTypeEnum = {
         CONST: 0,
         NEGATION: 1,
@@ -270,7 +266,7 @@ export function EditFilterExpressionDialog(props) {
         } else if (val == FilterTypeEnum.IMAGETYPE) {
             setFilter(new ImageTypeFilter(filter.result_type, ImageTypeEnum.PHOTO));
         } else if (val == FilterTypeEnum.LOCATION) {
-            setFilter(new LocationFilter(filter.result_type, [[0.0, 0.0]], polygons_dispatch));
+            setFilter(new LocationFilter(filter.result_type, [[0.0, 0.0]]));
         } else {
             throw new Error('Unsupported filter type: ' + val);
         }
@@ -483,12 +479,12 @@ export function LogicalOperatorFilterExpressionControl(props) {
                 <Box className={classes.logic_op_sbs}>
                     <Box>
                         <Box className={classes.logic_op_subexpr}>
-                            <FilterExpressionControl expr={expr.sub_filter_a} onChange={handleAChanged} isRoot={false} />
+                            <FilterExpressionControl expr={expr.sub_filter_a} onChange={handleAChanged} mayBeRemoved={true} />
                         </Box>
                     </Box>
                     <Box>
                         <Box className={classes.logic_op_subexpr}>
-                            <FilterExpressionControl expr={expr.sub_filter_b} onChange={handleBChanged} isRoot={false} />
+                            <FilterExpressionControl expr={expr.sub_filter_b} onChange={handleBChanged} mayBeRemoved={true} />
                         </Box>
                     </Box>
                 </Box>
@@ -532,13 +528,16 @@ export function NegationExpressionControl(props) {
         onChange(new_filter);
     }
 
+    // Only nodes which are transformation nodes may normally be removed.
+    const may_be_removed = expr instanceof NegationFilter;
+
     return (
         <>
             <Box className={classes.logic_op_outer}>
                 <Box className={classes.logic_op_sbs}>
                     <Box>
                         <Box className={classes.logic_op_subexpr}>
-                            <FilterExpressionControl expr={expr.body} onChange={handleBodyChanged} isRoot={false} />
+                            <FilterExpressionControl expr={expr.body} onChange={handleBodyChanged} mayBeRemoved={may_be_removed} />
                         </Box>
                     </Box>
                 </Box>
@@ -624,7 +623,7 @@ export function LocationFilterExpressionControl(props) {
 }
 
 export function FilterExpressionControl(props) {
-    const { expr, onChange, isRoot } = props;
+    const { expr, onChange, mayBeRemoved } = props;
     const [anchorEl, setAnchorEl] = React.useState(null);
     const [editDialogOpen, setEditDialogOpen] = React.useState(false);
     const [combineDialogOpen, setCombineDialogOpen] = React.useState(false);
@@ -718,11 +717,6 @@ export function FilterExpressionControl(props) {
         throw new Error('Unsupported filter expression');
     }
 
-    // If this is the root node, removing it is not allowed.
-    // Other nodes may be removed.
-    // The only exception is a negation node: removing that will replace it by its child.
-    var allowRemove = !isRoot || (expr instanceof NegationFilter);
-
     return (
         <>
             {filter_elem}
@@ -737,7 +731,7 @@ export function FilterExpressionControl(props) {
                 <MenuItem onClick={handleAnd}>And...</MenuItem>
                 <MenuItem onClick={handleOr}>Or...</MenuItem>
                 <MenuItem onClick={handleNegation}>Negate</MenuItem>
-                {allowRemove && <MenuItem onClick={handleRemove}>Remove</MenuItem>}
+                {mayBeRemoved && <MenuItem onClick={handleRemove}>Remove</MenuItem>}
             </Menu>
             <EditFilterExpressionDialog
                 onClose={handleCloseEditFilterDialog}
@@ -768,6 +762,10 @@ export function FilterControl(props) {
         }
     }
 
+    // The root node may in principle never be removed,
+    // except if it is a transformation node (then the body becomes the new root).
+    const may_be_removed = filter instanceof NegationFilter;
+
     return (
         <>
             <Box className={classes.filtercontrol}>
@@ -781,7 +779,7 @@ export function FilterControl(props) {
                     }
                     label={resultTypeString + ':'}
                 />
-                <FilterExpressionControl expr={filter} onChange={onChange} isRoot={true} />
+                <FilterExpressionControl expr={filter} onChange={onChange} mayBeRemoved={may_be_removed} />
             </Box>
         </>
     );
diff --git a/yarn.lock b/yarn.lock
index 3728018..0acfb3f 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7252,6 +7252,11 @@ object-hash@^1.3.1:
   resolved "https://registry.yarnpkg.com/object-hash/-/object-hash-1.3.1.tgz#fde452098a951cb145f039bb7d455449ddc126df"
   integrity sha512-OSuu/pU4ENM9kmREg0BdNrUDIl1heYa4mBZacJc+vVWz4GtAwu7jO8s4AIt2aGRUTqxykpWzI3Oqnsm13tTMDA==
 
+object-hash@^2.0.1:
+  version "2.0.1"
+  resolved "https://registry.yarnpkg.com/object-hash/-/object-hash-2.0.1.tgz#cef18a0c940cc60aa27965ecf49b782cbf101d96"
+  integrity sha512-HgcGMooY4JC2PBt9sdUdJ6PMzpin+YtY3r/7wg0uTifP+HJWW8rammseSEHuyt0UeShI183UGssCJqm1bJR7QA==
+
 object-inspect@^1.7.0:
   version "1.7.0"
   resolved "https://registry.yarnpkg.com/object-inspect/-/object-inspect-1.7.0.tgz#f4f6bd181ad77f006b5ece60bd0b6f398ff74a67"