Subject: [PATCH v6 4/8] Add support for implementing custom COPY TO format as extension

From: Sutou Kouhei <[email-masked]>
Date: Tue, 23 Jan 2024 15:12:43 +0900

* Add CopyToStateData::opaque that can be used to keep data for custom
  COPY TO format implementation
* Export CopySendEndOfRow() to flush data in CopyToStateData::fe_msgbuf
* Rename CopySendEndOfRow() to CopyToStateFlush() because it's a
  method for CopyToState and it's used for flushing. End-of-row related
  codes were moved to CopyToTextSendEndOfRow().
---
 src/backend/commands/copyto.c  | 15 +++++++--------
 src/include/commands/copyapi.h |  5 +++++
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index cfc74ee7b1..b5d8678394 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -69,7 +69,6 @@ static void SendCopyEnd(CopyToState cstate);
 static void CopySendData(CopyToState cstate, const void *databuf, int datasize);
 static void CopySendString(CopyToState cstate, const char *str);
 static void CopySendChar(CopyToState cstate, char c);
-static void CopySendEndOfRow(CopyToState cstate);
 static void CopySendInt32(CopyToState cstate, int32 val);
 static void CopySendInt16(CopyToState cstate, int16 val);
 
@@ -117,7 +116,7 @@ CopyToTextSendEndOfRow(CopyToState cstate)
 		default:
 			break;
 	}
-	CopySendEndOfRow(cstate);
+	CopyToStateFlush(cstate);
 }
 
 static void
@@ -302,7 +301,7 @@ CopyToBinaryOneRow(CopyToState cstate, TupleTableSlot *slot)
 		}
 	}
 
-	CopySendEndOfRow(cstate);
+	CopyToStateFlush(cstate);
 }
 
 static void
@@ -311,7 +310,7 @@ CopyToBinaryEnd(CopyToState cstate)
 	/* Generate trailer for a binary copy */
 	CopySendInt16(cstate, -1);
 	/* Need to flush out the trailer */
-	CopySendEndOfRow(cstate);
+	CopyToStateFlush(cstate);
 }
 
 CopyToRoutine CopyToRoutineText = {
@@ -377,8 +376,8 @@ SendCopyEnd(CopyToState cstate)
  * CopySendData sends output data to the destination (file or frontend)
  * CopySendString does the same for null-terminated strings
  * CopySendChar does the same for single characters
- * CopySendEndOfRow does the appropriate thing at end of each data row
- *	(data is not actually flushed except by CopySendEndOfRow)
+ * CopyToStateFlush flushes the buffered data
+ *	(data is not actually flushed except by CopyToStateFlush)
  *
  * NB: no data conversion is applied by these functions
  *----------
@@ -401,8 +400,8 @@ CopySendChar(CopyToState cstate, char c)
 	appendStringInfoCharMacro(cstate->fe_msgbuf, c);
 }
 
-static void
-CopySendEndOfRow(CopyToState cstate)
+void
+CopyToStateFlush(CopyToState cstate)
 {
 	StringInfo	fe_msgbuf = cstate->fe_msgbuf;
 
diff --git a/src/include/commands/copyapi.h b/src/include/commands/copyapi.h
index a869d78d72..ffad433a21 100644
--- a/src/include/commands/copyapi.h
+++ b/src/include/commands/copyapi.h
@@ -174,6 +174,11 @@ typedef struct CopyToStateData
 	FmgrInfo   *out_functions;	/* lookup info for output functions */
 	MemoryContext rowcontext;	/* per-row evaluation context */
 	uint64		bytes_processed;	/* number of bytes processed so far */
+
+	/* For custom format implementation */
+	void	   *opaque;			/* private space */
 } CopyToStateData;
 
+extern void CopyToStateFlush(CopyToState cstate);
+
 #endif							/* COPYAPI_H */
-- 
2.43.0

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