Subject: [PATCH v18 5/5] Add support for implementing custom COPY TO/FROM format as extension

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

For custom COPY TO format implementation:

* 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().

For custom COPY FROM format implementation:

* Add CopyFromStateData::opaque that can be used to keep data for
  custom COPY From format implementation
* Export CopyReadBinaryData() to read the next data
* Rename CopyReadBinaryData() to CopyFromStateRead() because it's a
  method for CopyFromState and "BinaryData" is redundant.
---
 src/backend/commands/copyfromparse.c | 21 ++++++++++-----------
 src/backend/commands/copyto.c        | 15 +++++++--------
 src/include/commands/copyapi.h       | 10 ++++++++++
 3 files changed, 27 insertions(+), 19 deletions(-)

diff --git a/src/backend/commands/copyfromparse.c b/src/backend/commands/copyfromparse.c
index 74844103228..cd80d34f3da 100644
--- a/src/backend/commands/copyfromparse.c
+++ b/src/backend/commands/copyfromparse.c
@@ -164,7 +164,6 @@ static int	CopyGetData(CopyFromState cstate, void *databuf,
 static inline bool CopyGetInt32(CopyFromState cstate, int32 *val);
 static inline bool CopyGetInt16(CopyFromState cstate, int16 *val);
 static void CopyLoadInputBuf(CopyFromState cstate);
-static int	CopyReadBinaryData(CopyFromState cstate, char *dest, int nbytes);
 
 void
 ReceiveCopyBegin(CopyFromState cstate)
@@ -193,7 +192,7 @@ ReceiveCopyBinaryHeader(CopyFromState cstate)
 	int32		tmp;
 
 	/* Signature */
-	if (CopyReadBinaryData(cstate, readSig, 11) != 11 ||
+	if (CopyFromStateRead(cstate, readSig, 11) != 11 ||
 		memcmp(readSig, BinarySignature, 11) != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
@@ -221,7 +220,7 @@ ReceiveCopyBinaryHeader(CopyFromState cstate)
 	/* Skip extension header, if present */
 	while (tmp-- > 0)
 	{
-		if (CopyReadBinaryData(cstate, readSig, 1) != 1)
+		if (CopyFromStateRead(cstate, readSig, 1) != 1)
 			ereport(ERROR,
 					(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
 					 errmsg("invalid COPY file header (wrong length)")));
@@ -363,7 +362,7 @@ CopyGetInt32(CopyFromState cstate, int32 *val)
 {
 	uint32		buf;
 
-	if (CopyReadBinaryData(cstate, (char *) &buf, sizeof(buf)) != sizeof(buf))
+	if (CopyFromStateRead(cstate, (char *) &buf, sizeof(buf)) != sizeof(buf))
 	{
 		*val = 0;				/* suppress compiler warning */
 		return false;
@@ -380,7 +379,7 @@ CopyGetInt16(CopyFromState cstate, int16 *val)
 {
 	uint16		buf;
 
-	if (CopyReadBinaryData(cstate, (char *) &buf, sizeof(buf)) != sizeof(buf))
+	if (CopyFromStateRead(cstate, (char *) &buf, sizeof(buf)) != sizeof(buf))
 	{
 		*val = 0;				/* suppress compiler warning */
 		return false;
@@ -691,14 +690,14 @@ CopyLoadInputBuf(CopyFromState cstate)
 }
 
 /*
- * CopyReadBinaryData
+ * CopyFromStateRead
  *
  * Reads up to 'nbytes' bytes from cstate->copy_file via cstate->raw_buf
  * and writes them to 'dest'.  Returns the number of bytes read (which
  * would be less than 'nbytes' only if we reach EOF).
  */
-static int
-CopyReadBinaryData(CopyFromState cstate, char *dest, int nbytes)
+int
+CopyFromStateRead(CopyFromState cstate, char *dest, int nbytes)
 {
 	int			copied_bytes = 0;
 
@@ -1078,7 +1077,7 @@ CopyFromBinaryOneRow(CopyFromState cstate, ExprContext *econtext,
 		 */
 		char		dummy;
 
-		if (CopyReadBinaryData(cstate, &dummy, 1) > 0)
+		if (CopyFromStateRead(cstate, &dummy, 1) > 0)
 			ereport(ERROR,
 					(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
 					 errmsg("received copy data after EOF marker")));
@@ -2103,8 +2102,8 @@ CopyReadBinaryAttribute(CopyFromState cstate, FmgrInfo *flinfo,
 	resetStringInfo(&cstate->attribute_buf);
 
 	enlargeStringInfo(&cstate->attribute_buf, fld_size);
-	if (CopyReadBinaryData(cstate, cstate->attribute_buf.data,
-						   fld_size) != fld_size)
+	if (CopyFromStateRead(cstate, cstate->attribute_buf.data,
+						  fld_size) != fld_size)
 		ereport(ERROR,
 				(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
 				 errmsg("unexpected EOF in COPY data")));
diff --git a/src/backend/commands/copyto.c b/src/backend/commands/copyto.c
index 54aa6cdecaf..cd9e352533a 100644
--- a/src/backend/commands/copyto.c
+++ b/src/backend/commands/copyto.c
@@ -63,7 +63,6 @@ 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);
 
@@ -99,7 +98,7 @@ CopyToTextLikeSendEndOfRow(CopyToState cstate)
 	}
 
 	/* Now take the actions related to the end of a row */
-	CopySendEndOfRow(cstate);
+	CopyToStateFlush(cstate);
 }
 
 /*
@@ -325,7 +324,7 @@ CopyToBinaryOneRow(CopyToState cstate, TupleTableSlot *slot)
 		}
 	}
 
-	CopySendEndOfRow(cstate);
+	CopyToStateFlush(cstate);
 }
 
 /*
@@ -339,7 +338,7 @@ CopyToBinaryEnd(CopyToState cstate)
 	/* Generate trailer for a binary copy */
 	CopySendInt16(cstate, -1);
 	/* Need to flush out the trailer */
-	CopySendEndOfRow(cstate);
+	CopyToStateFlush(cstate);
 }
 
 /*
@@ -419,8 +418,8 @@ 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
  *----------
@@ -443,8 +442,8 @@ 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 3104d99ea9f..0820b47a2d2 100644
--- a/src/include/commands/copyapi.h
+++ b/src/include/commands/copyapi.h
@@ -299,8 +299,13 @@ typedef struct CopyFromStateData
 #define RAW_BUF_BYTES(cstate) ((cstate)->raw_buf_len - (cstate)->raw_buf_index)
 
 	uint64		bytes_processed;	/* number of bytes processed so far */
+
+	/* For custom format implementation */
+	void	   *opaque;			/* private space */
 } CopyFromStateData;
 
+extern int	CopyFromStateRead(CopyFromState cstate, char *dest, int nbytes);
+
 
 typedef struct CopyToStateData *CopyToState;
 
@@ -401,6 +406,11 @@ 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 */
-- 
2.45.2

----Next_Part(Wed_Jul_24_17_30_59_2024_070)----