Add ESTIMATED_ENVELOPE system function

h2/src/docsrc/help/help.csv

@@ -4736,6 +4736,23 @@ Throw an SQLException with the passed SQLState and reason.
 CALL SIGNAL('23505', 'Duplicate user ID: ' || user_id);
 "
 
+"Functions (System)","ESTIMATED_ENVELOPE","
+ESTIMATED_ENVELOPE(tableNameString, columnNameString)
+","
+Returns the estimated minimum bounding box that encloses all specified GEOMETRY values.
+Only 2D coordinate plane is supported.
+NULL values are ignored.
+This function is only supported by MVStore engine.
+Column must have a spatial index.
+This function is fast, but estimation may include uncommitted data (including data from other transactions),
+may return approximate bounds, or be different with actual value due to other reasons.
+Use with caution.
+If estimation is not available this function returns NULL.
+For accurate and reliable result use ESTIMATE aggregate function instead.
+","
+CALL ESTIMATED_ENVELOPE('MY_TABLE', 'GEOMETRY_COLUMN');
+"
+
 "Functions (System)","FILE_READ","
 FILE_READ(fileNameString [,encodingString])
 ","

h2/src/main/org/h2/expression/Function.java

@@ -27,9 +27,11 @@ import org.h2.engine.Constants;
 import org.h2.engine.Database;
 import org.h2.engine.Mode;
 import org.h2.engine.Session;
+import org.h2.index.Index;
 import org.h2.message.DbException;
 import org.h2.mode.FunctionsMSSQLServer;
 import org.h2.mode.FunctionsMySQL;
+import org.h2.mvstore.db.MVSpatialIndex;
 import org.h2.schema.Schema;
 import org.h2.schema.Sequence;
 import org.h2.security.BlockCipher;
@@ -116,7 +118,7 @@ public class Function extends Expression implements FunctionCall {
     public static final int DATABASE = 150, USER = 151, CURRENT_USER = 152,
             IDENTITY = 153, SCOPE_IDENTITY = 154, AUTOCOMMIT = 155,
             READONLY = 156, DATABASE_PATH = 157, LOCK_TIMEOUT = 158,
-            DISK_SPACE_USED = 159, SIGNAL = 160;
+            DISK_SPACE_USED = 159, SIGNAL = 160, ESTIMATED_ENVELOPE = 161;
 
     private static final Pattern SIGNAL_PATTERN = Pattern.compile("[0-9A-Z]{5}");
 
@@ -456,6 +458,7 @@ public class Function extends Expression implements FunctionCall {
         addFunctionNotDeterministic("DISK_SPACE_USED", DISK_SPACE_USED,
                 1, Value.LONG);
         addFunctionWithNull("SIGNAL", SIGNAL, 2, Value.NULL);
+        addFunctionNotDeterministic("ESTIMATED_ENVELOPE", ESTIMATED_ENVELOPE, 2, Value.LONG);
         addFunction("H2VERSION", H2VERSION, 0, Value.STRING);
 
         // TableFunction
@@ -883,6 +886,9 @@ public class Function extends Expression implements FunctionCall {
         case DISK_SPACE_USED:
             result = ValueLong.get(getDiskSpaceUsed(session, v0));
             break;
+        case ESTIMATED_ENVELOPE:
+            result = getEstimatedEnvelope(session, v0, values[1]);
+            break;
         case CAST:
         case CONVERT: {
             Mode mode = database.getMode();
@@ -1096,11 +1102,27 @@ public class Function extends Expression implements FunctionCall {
         return false;
     }
 
-    private static long getDiskSpaceUsed(Session session, Value v0) {
-        Parser p = new Parser(session);
-        String sql = v0.getString();
-        Table table = p.parseTableName(sql);
-        return table.getDiskSpaceUsed();
+    private static long getDiskSpaceUsed(Session session, Value tableName) {
+        return getTable(session, tableName).getDiskSpaceUsed();
+    }
+
+    private static Value getEstimatedEnvelope(Session session, Value tableName, Value columnName) {
+        Table table = getTable(session, tableName);
+        Column column = table.getColumn(columnName.getString());
+        ArrayList<Index> indexes = table.getIndexes();
+        if (indexes != null) {
+            for (int i = 1, size = indexes.size(); i < size; i++) {
+                Index index = indexes.get(i);
+                if (index instanceof MVSpatialIndex && index.isFirstColumn(column)) {
+                    return ((MVSpatialIndex) index).getEstimatedBounds(session);
+                }
+            }
+        }
+        return ValueNull.INSTANCE;
+    }
+
+    private static Table getTable(Session session, Value tableName) {
+        return new Parser(session).parseTableName(tableName.getString());
     }
 
     protected static Value getNullOrValue(Session session, Expression[] args,

h2/src/main/org/h2/mvstore/db/MVSpatialIndex.java

@@ -234,6 +234,42 @@ public class MVSpatialIndex extends BaseIndex implements SpatialIndex, MVIndex {
         return cursor.getBounds();
     }
 
+    /**
+     * Returns the estimated minimum bounding box that encloses all keys.
+     *
+     * The returned value may be incorrect.
+     *
+     * @param session the session
+     * @return the estimated minimum bounding box that encloses all keys, or null
+     */
+    public Value getEstimatedBounds(Session session) {
+        Page p = spatialMap.getRootPage();
+        int count = p.getKeyCount();
+        if (count > 0) {
+            SpatialKey key = (SpatialKey) p.getKey(0);
+            float bminxf = key.min(0), bmaxxf = key.max(0), bminyf = key.min(1), bmaxyf = key.max(1);
+            for (int i = 1; i < count; i++) {
+                key = (SpatialKey) p.getKey(i);
+                float minxf = key.min(0), maxxf = key.max(0), minyf = key.min(1), maxyf = key.max(1);
+                if (minxf < bminxf) {
+                    bminxf = minxf;
+                }
+                if (maxxf > bmaxxf) {
+                    bmaxxf = maxxf;
+                }
+                if (minyf < bminyf) {
+                    bminyf = minyf;
+                }
+                if (maxyf > bmaxyf) {
+                    bmaxyf = maxyf;
+                }
+            }
+            return ValueGeometry.getFromGeometry(new GeometryFactory().toGeometry(
+                    new Envelope(bminxf, bmaxxf, bminyf, bmaxyf)));
+        }
+        return ValueNull.INSTANCE;
+    }
+
     private SpatialKey getKey(SearchRow row) {
         Value v = row.getValue(columnIds[0]);
         if (v == ValueNull.INSTANCE) {

h2/src/test/org/h2/test/scripts/functions/aggregate/envelope.sql

@@ -66,6 +66,9 @@ SELECT ENVELOPE(N) FROM (SELECT V AS N FROM TEST);
 SELECT ENVELOPE(V) FROM TEST;
 >> null
 
+SELECT ESTIMATED_ENVELOPE('TEST', 'V');
+>> null
+
 SELECT RAND(1000) * 0;
 >> 0.0
 
@@ -80,6 +83,10 @@ SELECT ENVELOPE(N) FROM (SELECT V AS N FROM TEST);
 SELECT ENVELOPE(V) FROM TEST;
 >> POLYGON ((68 78, 68 99951, 99903 99951, 99903 78, 68 78))
 
+SELECT ESTIMATED_ENVELOPE('TEST', 'V');
+#+mvStore#>> POLYGON ((68 78, 68 99951, 99903 99951, 99903 78, 68 78))
+#-mvStore#>> null
+
 TRUNCATE TABLE TEST;
 > ok
 

h2/src/tools/org/h2/build/doc/dictionary.txt

@@ -789,6 +789,6 @@ inconsistencies discover eliminated violates tweaks postpone leftovers
 tied ties
 launched unavailable smallmoney erroneously multiplier newid pan streamline unmap preview unexpectedly presumably
 converging smth rng curs casts unmapping unmapper
-immediate hhmmss scheduled hhmm prematurely postponed arranges subexpression subexpressions encloses plane
+immediate hhmmss scheduled hhmm prematurely postponed arranges subexpression subexpressions encloses plane caution
 minxf maxxf minyf maxyf bminxf bmaxxf bminyf bmaxyf
 minxd maxxd minyd maxyd bminxd bmaxxd bminyd bmaxyd