From 22daacbd77c6dd0e13fe11e30fba90f7595ff6c1 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Mon, 4 Mar 2024 13:52:34 +0900
Subject: [PATCH v18 1/5] Add CopyFromRoutine/CopyToRountine

They are for implementing custom COPY FROM/TO format. But this is not
enough to implement custom COPY FROM/TO format yet. We'll export some
APIs to receive/send data and add "format" option to COPY FROM/TO
later.

Existing text/csv/binary format implementations don't use
CopyFromRoutine/CopyToRoutine for now. We have a patch for it but we
defer it. Because there are some mysterious profile results in spite
of we get faster runtimes. See [1] for details.

[1] https://www.postgresql.org/message-id/ZdbtQJ-p5H1_EDwE%40paquier.xyz

Note that this doesn't change existing text/csv/binary format
implementations.
---
 src/backend/commands/copyfrom.c          |  24 +++++-
 src/backend/commands/copyfromparse.c     |   5 ++
 src/backend/commands/copyto.c            |  31 ++++++-
 src/include/commands/copyapi.h           | 100 +++++++++++++++++++++++
 src/include/commands/copyfrom_internal.h |   4 +
 src/tools/pgindent/typedefs.list         |   2 +
 6 files changed, 158 insertions(+), 8 deletions(-)
 create mode 100644 src/include/commands/copyapi.h

diff --git a/src/backend/commands/copyfrom.c b/src/backend/commands/copyfrom.c
index ce4d62e707c..ff13b3e3592 100644
--- a/src/backend/commands/copyfrom.c
+++ b/src/backend/commands/copyfrom.c
@@ -1618,12 +1618,22 @@ BeginCopyFrom(ParseState *pstate,
 
 		/* Fetch the input function and typioparam info */
 		if (cstate->opts.binary)
+		{
 			getTypeBinaryInputInfo(att->atttypid,
 								   &in_func_oid, &typioparams[attnum - 1]);
+			fmgr_info(in_func_oid, &in_functions[attnum - 1]);
+		}
+		else if (cstate->routine)
+			cstate->routine->CopyFromInFunc(cstate, att->atttypid,
+											&in_functions[attnum - 1],
+											&typioparams[attnum - 1]);
+
 		else
+		{
 			getTypeInputInfo(att->atttypid,
 							 &in_func_oid, &typioparams[attnum - 1]);
-		fmgr_info(in_func_oid, &in_functions[attnum - 1]);
+			fmgr_info(in_func_oid, &in_functions[attnum - 1]);
+		}
 
 		/* Get default info if available */
 		defexprs[attnum - 1] = NULL;
@@ -1763,10 +1773,13 @@ BeginCopyFrom(ParseState *pstate,
 		/* Read and verify binary header */
 		ReceiveCopyBinaryHeader(cstate);
 	}
-
-	/* create workspace for CopyReadAttributes results */
-	if (!cstate->opts.binary)
+	else if (cstate->routine)
 	{
+		cstate->routine->CopyFromStart(cstate, tupDesc);
+	}
+	else
+	{
+		/* create workspace for CopyReadAttributes results */
 		AttrNumber	attr_count = list_length(cstate->attnumlist);
 
 		cstate->max_fields = attr_count;
@@ -1784,6 +1797,9 @@ BeginCopyFrom(ParseState *pstate,
 void
 EndCopyFrom(CopyFromState cstate)
 {
+	if (cstate->routine)
+		cstate->routine->CopyFromEnd(cstate);
+
 	/* No COPY FROM related resources except memory. */
 	if (cstate->is_program)
 	{
diff --git a/src/backend/commands/copyfromparse.c b/src/backend/commands/copyfromparse.c
index 7efcb891598..92b8d5e72d5 100644
--- a/src/backend/commands/copyfromparse.c
+++ b/src/backend/commands/copyfromparse.c
@@ -1012,6 +1012,11 @@ NextCopyFrom(CopyFromState cstate, ExprContext *econtext,
 
 		Assert(fieldno == attr_count);
 	}
+	else if (cstate->routine)
+	{
+		if (!cstate->routine->CopyFromOneRow(cstate, econtext, values, nulls))
+			return false;
+	}
 	else
 	{
 		/* binary */
diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index ae8b2e36d72..ff19c457abf 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -20,6 +20,7 @@
 
 #include "access/tableam.h"
 #include "commands/copy.h"
+#include "commands/copyapi.h"
 #include "commands/progress.h"
 #include "executor/execdesc.h"
 #include "executor/executor.h"
@@ -64,6 +65,9 @@ typedef enum CopyDest
  */
 typedef struct CopyToStateData
 {
+	/* format routine */
+	const CopyToRoutine *routine;
+
 	/* low-level state data */
 	CopyDest	copy_dest;		/* type of copy source/destination */
 	FILE	   *copy_file;		/* used if copy_dest == COPY_FILE */
@@ -771,14 +775,22 @@ DoCopyTo(CopyToState cstate)
 		Form_pg_attribute attr = TupleDescAttr(tupDesc, attnum - 1);
 
 		if (cstate->opts.binary)
+		{
 			getTypeBinaryOutputInfo(attr->atttypid,
 									&out_func_oid,
 									&isvarlena);
+			fmgr_info(out_func_oid, &cstate->out_functions[attnum - 1]);
+		}
+		else if (cstate->routine)
+			cstate->routine->CopyToOutFunc(cstate, attr->atttypid,
+										   &cstate->out_functions[attnum - 1]);
 		else
+		{
 			getTypeOutputInfo(attr->atttypid,
 							  &out_func_oid,
 							  &isvarlena);
-		fmgr_info(out_func_oid, &cstate->out_functions[attnum - 1]);
+			fmgr_info(out_func_oid, &cstate->out_functions[attnum - 1]);
+		}
 	}
 
 	/*
@@ -805,6 +817,8 @@ DoCopyTo(CopyToState cstate)
 		tmp = 0;
 		CopySendInt32(cstate, tmp);
 	}
+	else if (cstate->routine)
+		cstate->routine->CopyToStart(cstate, tupDesc);
 	else
 	{
 		/*
@@ -886,6 +900,8 @@ DoCopyTo(CopyToState cstate)
 		/* Need to flush out the trailer */
 		CopySendEndOfRow(cstate);
 	}
+	else if (cstate->routine)
+		cstate->routine->CopyToEnd(cstate);
 
 	MemoryContextDelete(cstate->rowcontext);
 
@@ -910,15 +926,22 @@ CopyOneRowTo(CopyToState cstate, TupleTableSlot *slot)
 	MemoryContextReset(cstate->rowcontext);
 	oldcontext = MemoryContextSwitchTo(cstate->rowcontext);
 
+	/* Make sure the tuple is fully deconstructed */
+	slot_getallattrs(slot);
+
+	if (cstate->routine)
+	{
+		cstate->routine->CopyToOneRow(cstate, slot);
+		MemoryContextSwitchTo(oldcontext);
+		return;
+	}
+
 	if (cstate->opts.binary)
 	{
 		/* Binary per-tuple header */
 		CopySendInt16(cstate, list_length(cstate->attnumlist));
 	}
 
-	/* Make sure the tuple is fully deconstructed */
-	slot_getallattrs(slot);
-
 	foreach(cur, cstate->attnumlist)
 	{
 		int			attnum = lfirst_int(cur);
diff --git a/src/include/commands/copyapi.h b/src/include/commands/copyapi.h
new file mode 100644
index 00000000000..635c4cbff27
--- /dev/null
+++ b/src/include/commands/copyapi.h
@@ -0,0 +1,100 @@
+/*-------------------------------------------------------------------------
+ *
+ * copyapi.h
+ *	  API for COPY TO/FROM handlers
+ *
+ *
+ * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/commands/copyapi.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef COPYAPI_H
+#define COPYAPI_H
+
+#include "executor/tuptable.h"
+#include "nodes/execnodes.h"
+
+/* These are private in commands/copy[from|to].c */
+typedef struct CopyFromStateData *CopyFromState;
+typedef struct CopyToStateData *CopyToState;
+
+/*
+ * API structure for a COPY FROM format implementation.  Note this must be
+ * allocated in a server-lifetime manner, typically as a static const struct.
+ */
+typedef struct CopyFromRoutine
+{
+	/*
+	 * Called when COPY FROM is started to set up the input functions
+	 * associated to the relation's attributes writing to.  `finfo` can be
+	 * optionally filled to provide the catalog information of the input
+	 * function.  `typioparam` can be optionally filled to define the OID of
+	 * the type to pass to the input function.  `atttypid` is the OID of data
+	 * type used by the relation's attribute.
+	 */
+	void		(*CopyFromInFunc) (CopyFromState cstate, Oid atttypid,
+								   FmgrInfo *finfo, Oid *typioparam);
+
+	/*
+	 * Called when COPY FROM is started.
+	 *
+	 * `tupDesc` is the tuple descriptor of the relation where the data needs
+	 * to be copied.  This can be used for any initialization steps required
+	 * by a format.
+	 */
+	void		(*CopyFromStart) (CopyFromState cstate, TupleDesc tupDesc);
+
+	/*
+	 * Copy one row to a set of `values` and `nulls` of size tupDesc->natts.
+	 *
+	 * 'econtext' is used to evaluate default expression for each column that
+	 * is either not read from the file or is using the DEFAULT option of COPY
+	 * FROM.  It is NULL if no default values are used.
+	 *
+	 * Returns false if there are no more tuples to copy.
+	 */
+	bool		(*CopyFromOneRow) (CopyFromState cstate, ExprContext *econtext,
+								   Datum *values, bool *nulls);
+
+	/* Called when COPY FROM has ended. */
+	void		(*CopyFromEnd) (CopyFromState cstate);
+} CopyFromRoutine;
+
+/*
+ * API structure for a COPY TO format implementation.   Note this must be
+ * allocated in a server-lifetime manner, typically as a static const struct.
+ */
+typedef struct CopyToRoutine
+{
+	/*
+	 * Called when COPY TO is started to set up the output functions
+	 * associated to the relation's attributes reading from.  `finfo` can be
+	 * optionally filled.  `atttypid` is the OID of data type used by the
+	 * relation's attribute.
+	 */
+	void		(*CopyToOutFunc) (CopyToState cstate, Oid atttypid,
+								  FmgrInfo *finfo);
+
+	/*
+	 * Called when COPY TO is started.
+	 *
+	 * `tupDesc` is the tuple descriptor of the relation from where the data
+	 * is read.
+	 */
+	void		(*CopyToStart) (CopyToState cstate, TupleDesc tupDesc);
+
+	/*
+	 * Copy one row for COPY TO.
+	 *
+	 * `slot` is the tuple slot where the data is emitted.
+	 */
+	void		(*CopyToOneRow) (CopyToState cstate, TupleTableSlot *slot);
+
+	/* Called when COPY TO has ended */
+	void		(*CopyToEnd) (CopyToState cstate);
+} CopyToRoutine;
+
+#endif							/* COPYAPI_H */
diff --git a/src/include/commands/copyfrom_internal.h b/src/include/commands/copyfrom_internal.h
index cad52fcc783..509b9e92a18 100644
--- a/src/include/commands/copyfrom_internal.h
+++ b/src/include/commands/copyfrom_internal.h
@@ -15,6 +15,7 @@
 #define COPYFROM_INTERNAL_H
 
 #include "commands/copy.h"
+#include "commands/copyapi.h"
 #include "commands/trigger.h"
 #include "nodes/miscnodes.h"
 
@@ -58,6 +59,9 @@ typedef enum CopyInsertMethod
  */
 typedef struct CopyFromStateData
 {
+	/* format routine */
+	const CopyFromRoutine *routine;
+
 	/* low-level state data */
 	CopySource	copy_src;		/* type of copy source */
 	FILE	   *copy_file;		/* used if copy_src == COPY_FILE */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index b4d7f9217ce..3ce855c8f17 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -490,6 +490,7 @@ ConvertRowtypeExpr
 CookedConstraint
 CopyDest
 CopyFormatOptions
+CopyFromRoutine
 CopyFromState
 CopyFromStateData
 CopyHeaderChoice
@@ -501,6 +502,7 @@ CopyMultiInsertInfo
 CopyOnErrorChoice
 CopySource
 CopyStmt
+CopyToRoutine
 CopyToState
 CopyToStateData
 Cost
-- 
2.45.2

