Add support for const functions in CASE expressions

src/query_handler_test.go

@@ -542,6 +542,10 @@ func TestHandleQuery(t *testing.T) {
 			"description": {"id", "name", "is_superuser", "can_create_role"},
 			"values":      {},
 		},
+		"SELECT CASE WHEN TRUE THEN pg_catalog.pg_is_in_recovery() END AS CASE": {
+			"description": {"case"},
+			"values":      {"f"},
+		},
 		// WHERE pg functions
 		"SELECT gss_authenticated, encrypted FROM (SELECT false, false, false, false, false WHERE false) t(pid, gss_authenticated, principal, encrypted, credentials_delegated) WHERE pid = pg_backend_pid()": {
 			"description": {"gss_authenticated", "encrypted"},

src/select_remapper.go

@@ -170,6 +170,10 @@ func (selectRemapper *SelectRemapper) remapCaseExpressions(selectStatement *pgQu
 							subSelect := subLink.Subselect.GetSelectStmt()
 							subSelect = selectRemapper.remapSelectStatement(subSelect, indentLevel+1)
 						}
+						if funcCall := whenClause.Result.GetFuncCall(); funcCall != nil {
+							selectRemapper.traceTreeTraversal("CASE THEN function", indentLevel+1)
+							whenClause.Result = selectRemapper.remapperSelect.remappedToConstant(funcCall)
+						}
 					}
 				}
 			}
@@ -180,6 +184,10 @@ func (selectRemapper *SelectRemapper) remapCaseExpressions(selectStatement *pgQu
 					subSelect := subLink.Subselect.GetSelectStmt()
 					subSelect = selectRemapper.remapSelectStatement(subSelect, indentLevel+1)
 				}
+				if funcCall := caseExpr.Defresult.GetFuncCall(); funcCall != nil {
+					selectRemapper.traceTreeTraversal("CASE ELSE function", indentLevel+1)
+					caseExpr.Defresult = selectRemapper.remapperSelect.remappedToConstant(funcCall)
+				}
 			}
 		}
 	}

src/select_remapper_select.go

@@ -15,6 +15,7 @@ var REMAPPED_CONSTANT_BY_PG_FUNCTION_NAME = map[string]string{
 	"pg_tablespace_location":             "",
 	"pg_encoding_to_char":                "UTF8",
 	"pg_backend_pid":                     "0",
+	"pg_is_in_recovery":                  "f",
 }
 
 type SelectRemapperSelect struct {