Added cast for vector to real[]

CHANGELOG.md

@@ -1,6 +1,10 @@
+## 0.1.8 (unreleased)
+
+- Added cast for `vector` to `real[]`
+
 ## 0.1.7 (2021-06-13)
 
-- Added cast for `numeric[]`
+- Added cast for `numeric[]` to `vector`
 
 ## 0.1.6 (2021-06-09)
 

sql/vector--0.1.7--0.1.8.sql

@@ -0,0 +1,8 @@
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "ALTER EXTENSION vector UPDATE TO '0.1.8'" to load this file. \quit
+
+CREATE FUNCTION vector_to_float4(vector, integer, boolean) RETURNS real[]
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
+CREATE CAST (vector AS real[])
+	WITH FUNCTION vector_to_float4(vector, integer, boolean) AS IMPLICIT;

sql/vector.sql

@@ -100,6 +100,9 @@ CREATE FUNCTION array_to_vector(double precision[], integer, boolean) RETURNS ve
 CREATE FUNCTION array_to_vector(numeric[], integer, boolean) RETURNS vector
 	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION vector_to_float4(vector, integer, boolean) RETURNS real[]
+	AS 'MODULE_PATHNAME' LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 -- casts
 
 CREATE CAST (vector AS vector)
@@ -117,6 +120,9 @@ CREATE CAST (double precision[] AS vector)
 CREATE CAST (numeric[] AS vector)
 	WITH FUNCTION array_to_vector(numeric[], integer, boolean) AS IMPLICIT;
 
+CREATE CAST (vector AS real[])
+	WITH FUNCTION vector_to_float4(vector, integer, boolean) AS IMPLICIT;
+
 -- operators
 
 CREATE OPERATOR <-> (

src/vector.c

@@ -359,6 +359,29 @@ array_to_vector(PG_FUNCTION_ARGS)
 	PG_RETURN_POINTER(result);
 }
 
+/*
+ * Convert vector to float4[]
+ */
+PG_FUNCTION_INFO_V1(vector_to_float4);
+Datum
+vector_to_float4(PG_FUNCTION_ARGS)
+{
+	Vector	   *vec = PG_GETARG_VECTOR_P(0);
+	Datum	   *d;
+	ArrayType  *result;
+	int			i;
+
+	d = (Datum *) palloc(sizeof(Datum) * vec->dim);
+
+	for (i = 0; i < vec->dim; i++)
+		d[i] = Float4GetDatum(vec->x[i]);
+
+	/* Use TYPALIGN_INT for float4 */
+	result = construct_array(d, vec->dim, FLOAT4OID, sizeof(float4), true, TYPALIGN_INT);
+
+	PG_RETURN_POINTER(result);
+}
+
 /*
  * Get the L2 distance between vectors
  */

test/expected/cast.out

@@ -34,5 +34,11 @@ SELECT '{-Infinity}'::real[]::vector;
 ERROR:  infinite value not allowed in vector
 SELECT '{}'::real[]::vector;
 ERROR:  vector must have at least 1 dimension
+SELECT '[1,2,3]'::vector::real[];
+ float4  
+---------
+ {1,2,3}
+(1 row)
+
 SELECT array_agg(n)::vector FROM generate_series(1, 1025) n;
 ERROR:  vector cannot have more than 1024 dimensions

test/sql/cast.sql

@@ -10,4 +10,5 @@ SELECT '{NaN}'::real[]::vector;
 SELECT '{Infinity}'::real[]::vector;
 SELECT '{-Infinity}'::real[]::vector;
 SELECT '{}'::real[]::vector;
+SELECT '[1,2,3]'::vector::real[];
 SELECT array_agg(n)::vector FROM generate_series(1, 1025) n;