diff --git a/src/type_compat.rs b/src/type_compat.rs
index 5d1ba00..061f992 100644
--- a/src/type_compat.rs
+++ b/src/type_compat.rs
@@ -1,2 +1,3 @@
 pub(crate) mod geometry;
+pub(crate) mod map;
 pub(crate) mod pg_arrow_type_conversions;
diff --git a/src/type_compat/map.rs b/src/type_compat/map.rs
new file mode 100644
index 0000000..29b274b
--- /dev/null
+++ b/src/type_compat/map.rs
@@ -0,0 +1,169 @@
+use once_cell::sync::OnceCell;
+use pgrx::{
+    datum::UnboxDatum,
+    pg_sys::{
+        self, Anum_pg_type_oid, AsPgCStr, GetSysCacheOid, InvalidOid, Oid,
+        SysCacheIdentifier::TYPEOID,
+    },
+    prelude::PgHeapTuple,
+    AllocatedByRust, FromDatum, IntoDatum,
+};
+
+use crate::{
+    pgrx_missing_declerations::{get_extension_oid, get_extension_schema},
+    pgrx_utils::is_domain_of_array_type,
+};
+
+// we need to reset the crunchy_map context at each copy start
+static mut CRUNCHY_MAP_CONTEXT: OnceCell<CrunchyMapContext> = OnceCell::new();
+
+fn get_crunchy_map_context() -> &'static mut CrunchyMapContext {
+    unsafe {
+        CRUNCHY_MAP_CONTEXT
+            .get_mut()
+            .expect("crunchy_map context is not initialized")
+    }
+}
+
+pub(crate) fn reset_crunchy_map_context() {
+    unsafe { CRUNCHY_MAP_CONTEXT.take() };
+
+    unsafe {
+        CRUNCHY_MAP_CONTEXT
+            .set(CrunchyMapContext::new())
+            .expect("failed to reset crunchy_map context")
+    };
+}
+
+pub(crate) fn is_crunchy_map_typoid(typoid: Oid) -> bool {
+    let crunchy_map_context = get_crunchy_map_context();
+
+    if crunchy_map_context.crunchy_map_ext_schema_oid.is_none() {
+        return false;
+    }
+
+    // crunchy map is a domain type over array of key-value pairs
+    if !is_domain_of_array_type(typoid) {
+        return false;
+    }
+
+    let crunchy_map_ext_schema_oid = crunchy_map_context
+        .crunchy_map_ext_schema_oid
+        .expect("expected crunchy_map is created");
+
+    let found_typoid = unsafe {
+        GetSysCacheOid(
+            TYPEOID as _,
+            Anum_pg_type_oid as _,
+            typoid.into_datum().unwrap(),
+            crunchy_map_ext_schema_oid.into_datum().unwrap(),
+            pg_sys::Datum::from(0),
+            pg_sys::Datum::from(0),
+        )
+    };
+
+    let is_crunchy_map = found_typoid != InvalidOid;
+
+    if is_crunchy_map {
+        crunchy_map_context
+            .per_crunchy_map_context
+            .set_current_crunchy_map_typoid(typoid);
+    }
+
+    is_crunchy_map
+}
+
+#[derive(Debug, PartialEq, Clone)]
+struct CrunchyMapPerTypeContext {
+    current_crunchy_map_typoid: Option<Oid>,
+}
+
+impl CrunchyMapPerTypeContext {
+    fn set_current_crunchy_map_typoid(&mut self, typoid: Oid) {
+        self.current_crunchy_map_typoid = Some(typoid);
+    }
+}
+
+#[derive(Debug, PartialEq, Clone)]
+struct CrunchyMapContext {
+    crunchy_map_ext_oid: Option<Oid>,
+    crunchy_map_ext_schema_oid: Option<Oid>,
+    per_crunchy_map_context: CrunchyMapPerTypeContext,
+}
+
+impl CrunchyMapContext {
+    fn new() -> Self {
+        let crunchy_map_ext_oid = unsafe { get_extension_oid("crunchy_map".as_pg_cstr(), true) };
+        let crunchy_map_ext_oid = if crunchy_map_ext_oid == InvalidOid {
+            None
+        } else {
+            Some(crunchy_map_ext_oid)
+        };
+
+        let crunchy_map_ext_schema_oid = crunchy_map_ext_oid
+            .map(|crunchy_map_ext_oid| unsafe { get_extension_schema(crunchy_map_ext_oid) });
+
+        Self {
+            crunchy_map_ext_oid,
+            crunchy_map_ext_schema_oid,
+            per_crunchy_map_context: CrunchyMapPerTypeContext {
+                current_crunchy_map_typoid: None,
+            },
+        }
+    }
+}
+
+// crunchy_map is a domain type over array of key-value pairs
+pub(crate) struct CrunchyMap<'a> {
+    pub(crate) entries: pgrx::Array<'a, PgHeapTuple<'a, AllocatedByRust>>,
+}
+
+impl IntoDatum for CrunchyMap<'_> {
+    fn into_datum(self) -> Option<pg_sys::Datum> {
+        self.entries.into_datum()
+    }
+
+    fn type_oid() -> pg_sys::Oid {
+        get_crunchy_map_context()
+            .per_crunchy_map_context
+            .current_crunchy_map_typoid
+            .expect("crunchy_map type context is not initialized")
+    }
+}
+
+impl FromDatum for CrunchyMap<'_> {
+    unsafe fn from_polymorphic_datum(
+        datum: pg_sys::Datum,
+        is_null: bool,
+        _typoid: pg_sys::Oid,
+    ) -> Option<Self>
+    where
+        Self: Sized,
+    {
+        if is_null {
+            None
+        } else {
+            let entries = pgrx::Array::<PgHeapTuple<AllocatedByRust>>::from_datum(datum, false)
+                .expect("cannot convert datum to crunchy_map entries");
+
+            Some(CrunchyMap { entries })
+        }
+    }
+}
+
+unsafe impl<'a> UnboxDatum for CrunchyMap<'a> {
+    type As<'src> = Self
+    where
+        Self: 'src;
+
+    unsafe fn unbox<'src>(datum: pgrx::datum::Datum<'src>) -> Self::As<'src>
+    where
+        Self: 'src,
+    {
+        let entries =
+            pgrx::Array::<PgHeapTuple<AllocatedByRust>>::from_datum(datum.sans_lifetime(), false)
+                .expect("cannot convert datum to crunchy_map entries");
+
+        CrunchyMap { entries }
+    }
+}