Support MotherDuck views (#822)

This adds support for creating, querying and syncing VIEWs from
MotherDuck.

Views created by `CREATE VIEW` get created in MotherDuck if one of the
following conditions is met:

1. The view is created in a `ddb$` schema.
2. The query of the view accesses DuckDB tables or DuckDB views.
3. `duckdb.force_motherduck_views` is set to `true`.

Fixes #474

Author: JelteF

.github/workflows/docker.yaml

@@ -63,7 +63,7 @@ jobs:
 
           # If main or tag, then push to `pgduckdb/pgduckdb`
           git fetch --tags --force
-          if [ "$BRANCH" = "main" ] || git rev-parse --verify $BRANCH^{tag} > /dev/null 2>&1; then
+          if [ "$BRANCH" = "main" ] || [ "$BRANCH" = "duckdb-views" ] || git rev-parse --verify $BRANCH^{tag} > /dev/null 2>&1; then
             TARGET_REPO='pgduckdb/pgduckdb'
           else
             TARGET_REPO='pgduckdb/ci-builds'

include/pgduckdb/pg/declarations.hpp

@@ -87,5 +87,7 @@ struct PlanState;
 
 struct Plan;
 
+struct FuncExpr;
+
 typedef struct FunctionCallInfoBaseData *FunctionCallInfo;
 }

include/pgduckdb/pgduckdb_ddl.hpp

@@ -3,9 +3,12 @@
 #include "pgduckdb/pg/declarations.hpp"
 
 namespace pgduckdb {
-enum class DDLType { NONE, CREATE_TABLE, ALTER_TABLE, REFRESH_MATERIALIZED_VIEW };
+enum class DDLType { NONE, CREATE_TABLE, ALTER_TABLE, REFRESH_MATERIALIZED_VIEW, RENAME_VIEW };
 /* Tracks the type of DDL statement that is currently being executed */
 extern DDLType top_level_duckdb_ddl_type;
+bool IsMotherDuckView(Form_pg_class relation);
+bool IsMotherDuckView(Relation relation);
+FuncExpr *GetDuckdbViewExprFromQuery(Query *query);
 } // namespace pgduckdb
 
 void DuckdbTruncateTable(Oid relation_oid);

include/pgduckdb/pgduckdb_guc.hpp

@@ -19,6 +19,7 @@ extern int duckdb_threads_for_postgres_scan;
 extern int duckdb_max_workers_per_postgres_scan;
 extern char *duckdb_postgres_role;
 extern char *duckdb_motherduck_session_hint;
+extern bool duckdb_force_motherduck_views;
 extern char *duckdb_temporary_directory;
 extern char *duckdb_extension_directory;
 extern char *duckdb_max_temp_directory_size;

include/pgduckdb/pgduckdb_ruleutils.h

@@ -13,7 +13,7 @@ char *pgduckdb_function_name(Oid function_oid, bool *use_variadic_p);
 char *pgduckdb_get_querydef(Query *);
 char *pgduckdb_get_tabledef(Oid relation_id);
 char *pgduckdb_get_alter_tabledef(Oid relation_oid, AlterTableStmt *alter_stmt);
-char *pgduckdb_get_rename_tabledef(Oid relation_oid, RenameStmt *rename_stmt);
+char *pgduckdb_get_rename_relationdef(Oid relation_oid, RenameStmt *rename_stmt);
 bool pgduckdb_is_not_default_expr(Node *node, void *context);
 List *pgduckdb_db_and_schema(const char *postgres_schema_name, bool is_duckdb_table);
 const char *pgduckdb_db_and_schema_string(const char *postgres_schema_name, bool is_duckdb_table);
@@ -24,12 +24,15 @@ bool pgduckdb_var_is_duckdb_row(Var *var);
 bool pgduckdb_func_returns_duckdb_row(RangeTblFunction *rtfunc);
 Var *pgduckdb_duckdb_row_subscript_var(Expr *expr);
 bool pgduckdb_reconstruct_star_step(StarReconstructionContext *ctx, ListCell *tle_cell);
+bool pgduckdb_replace_subquery_with_view(Query *query, StringInfo buf);
 int pgduckdb_show_type(Const *constval, int original_showtype);
 bool pgduckdb_subscript_has_custom_alias(Plan *plan, List *rtable, Var *subscript_var, char *colname);
 SubscriptingRef *pgduckdb_strip_first_subscript(SubscriptingRef *sbsref, StringInfo buf);
 char *pgduckdb_write_row_refname(StringInfo buf, char *refname, bool is_top_level);
 bool is_system_sampling(const char *tsm_name, int num_args);
 bool is_bernoulli_sampling(const char *tsm_name, int num_args);
 void pgduckdb_add_tablesample_percent(const char *tsm_name, StringInfo buf, int num_args);
+char *pgduckdb_get_viewdef(const ViewStmt *stmt, const char *postgres_schema_name, const char *view_name,
+                           const char *duckdb_query_string);
 
 extern bool outermost_query;

include/pgduckdb/utility/rename_ruleutils.h

@@ -1,5 +1,8 @@
 #pragma once
 
+#include "postgres.h"
+#include "fmgr.h"
+
 /*
  * This file contains the renaming of the functions exposed by
  * vendor/pg_ruleutils.h functions to avoid conflicts with the PostgreSQL
@@ -29,3 +32,24 @@
  */
 #define generate_qualified_relation_name          pgduckdb_relation_name
 #define generate_relation_name(relid, namespaces) pgduckdb_relation_name(relid)
+
+#define declare_pgduckdb_ruleutils_function(original_name) extern Datum pgduckdb_##original_name(PG_FUNCTION_ARGS);
+
+#define pg_get_viewdef           pgduckdb_pg_get_viewdef
+#define pg_get_viewdef_ext       pgduckdb_pg_get_viewdef_ext
+#define pg_get_viewdef_wrap      pgduckdb_pg_get_viewdef_wrap
+#define pg_get_viewdef_name      pgduckdb_pg_get_viewdef_name
+#define pg_get_viewdef_name_ext  pgduckdb_pg_get_viewdef_name_ext
+#define pg_get_triggerdef        pgduckdb_pg_get_triggerdef
+#define pg_get_triggerdef_ext    pgduckdb_pg_get_triggerdef_ext
+#define pg_get_indexdef_name     pgduckdb_pg_get_indexdef_name
+#define pg_get_indexdef_name_ext pgduckdb_pg_get_indexdef_name_ext
+declare_pgduckdb_ruleutils_function(pg_get_viewdef);
+declare_pgduckdb_ruleutils_function(pg_get_viewdef_ext);
+declare_pgduckdb_ruleutils_function(pg_get_viewdef_wrap);
+declare_pgduckdb_ruleutils_function(pg_get_viewdef_name);
+declare_pgduckdb_ruleutils_function(pg_get_viewdef_name_ext);
+declare_pgduckdb_ruleutils_function(pg_get_triggerdef);
+declare_pgduckdb_ruleutils_function(pg_get_triggerdef_ext);
+declare_pgduckdb_ruleutils_function(pg_get_indexdef);
+declare_pgduckdb_ruleutils_function(pg_get_indexdef_ext);

sql/pg_duckdb--0.3.0--1.0.0.sql

@@ -781,3 +781,9 @@ LANGUAGE C AS 'MODULE_PATHNAME', 'pgduckdb_create_azure_secret';
 ALTER TABLE duckdb.extensions ADD COLUMN repository TEXT NOT NULL DEFAULT 'core';
 ALTER TABLE duckdb.extensions RENAME COLUMN enabled TO autoload;
 ALTER TABLE duckdb.extensions ALTER COLUMN autoload SET NOT NULL;
+
+CREATE FUNCTION duckdb.view(dbname text, schema text, view_name text, query text)
+RETURNS SETOF duckdb.row
+SET search_path = pg_catalog, pg_temp
+AS 'MODULE_PATHNAME', 'duckdb_only_function'
+LANGUAGE C;