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Improve performance of binary COPY FROM through better buffering.

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At least on Linux and macOS, fread() turns out to have far higher
per-call overhead than one could wish.  Reading 64KB of data at a time
and then parceling it out with our own memcpy logic makes binary COPY
from a file significantly faster --- around 30% in simple testing for
cases with narrow text columns (on Linux ... even more on macOS).

In binary COPY from frontend, there's no per-call fread(), and this
patch introduces an extra layer of memcpy'ing, but it still manages
to eke out a small win.  Apparently, the control-logic overhead in
CopyGetData() is enough to be worth avoiding for small fetches.

Bharath Rupireddy and Amit Langote, reviewed by Vignesh C,
cosmetic tweaks by me

Discussion: https://postgr.es/m/CALj2ACU5Bz06HWLwqSzNMN=Gupoj6Rcn_QVC+k070V4em9wu=A@mail.gmail.com
This commit is contained in:
Tom Lane 2020-07-25 16:34:35 -04:00
parent 8a37951eeb
commit 0a0727ccfc
1 changed files with 83 additions and 35 deletions
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118
src/backend/commands/copy.c
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@ -187,15 +187,15 @@ typedef struct CopyStateData
TransitionCaptureState *transition_capture;
/*
* These variables are used to reduce overhead in textual COPY FROM.
* These variables are used to reduce overhead in COPY FROM.
*
* attribute_buf holds the separated, de-escaped text for each field of
* the current line. The CopyReadAttributes functions return arrays of
* pointers into this buffer. We avoid palloc/pfree overhead by re-using
* the buffer on each cycle.
*
* (In binary COPY FROM, attribute_buf holds the binary data for the
* current field, while the other variables are not used.)
* In binary COPY FROM, attribute_buf holds the binary data for the
* current field, but the usage is otherwise similar.
*/
StringInfoData attribute_buf;
@ -209,7 +209,8 @@ typedef struct CopyStateData
* input cycle is first to read the whole line into line_buf, convert it
* to server encoding there, and then extract the individual attribute
* fields into attribute_buf. line_buf is preserved unmodified so that we
* can display it in error messages if appropriate.
* can display it in error messages if appropriate. (In binary mode,
* line_buf is not used.)
*/
StringInfoData line_buf;
bool line_buf_converted; /* converted to server encoding? */
@ -217,15 +218,18 @@ typedef struct CopyStateData
/*
* Finally, raw_buf holds raw data read from the data source (file or
* client connection). CopyReadLine parses this data sufficiently to
* locate line boundaries, then transfers the data to line_buf and
* converts it. Note: we guarantee that there is a \0 at
* raw_buf[raw_buf_len].
* client connection). In text mode, CopyReadLine parses this data
* sufficiently to locate line boundaries, then transfers the data to
* line_buf and converts it. In binary mode, CopyReadBinaryData fetches
* appropriate amounts of data from this buffer. In both modes, we
* guarantee that there is a \0 at raw_buf[raw_buf_len].
*/
#define RAW_BUF_SIZE 65536 /* we palloc RAW_BUF_SIZE+1 bytes */
char *raw_buf;
int raw_buf_index; /* next byte to process */
int raw_buf_len; /* total # of bytes stored */
/* Shorthand for number of unconsumed bytes available in raw_buf */
#define RAW_BUF_BYTES(cstate) ((cstate)->raw_buf_len - (cstate)->raw_buf_index)
} CopyStateData;
/* DestReceiver for COPY (query) TO */
@ -394,6 +398,8 @@ static void CopySendInt32(CopyState cstate, int32 val);
static bool CopyGetInt32(CopyState cstate, int32 *val);
static void CopySendInt16(CopyState cstate, int16 val);
static bool CopyGetInt16(CopyState cstate, int16 *val);
static bool CopyLoadRawBuf(CopyState cstate);
static int CopyReadBinaryData(CopyState cstate, char *dest, int nbytes);
/*
@ -723,7 +729,7 @@ CopyGetData(CopyState cstate, void *databuf, int minread, int maxread)
/*
* CopySendInt32 sends an int32 in network byte order
*/
static void
static inline void
CopySendInt32(CopyState cstate, int32 val)
{
uint32 buf;
@ -737,12 +743,12 @@ CopySendInt32(CopyState cstate, int32 val)
*
* Returns true if OK, false if EOF
*/
static bool
static inline bool
CopyGetInt32(CopyState cstate, int32 *val)
{
uint32 buf;
if (CopyGetData(cstate, &buf, sizeof(buf), sizeof(buf)) != sizeof(buf))
if (CopyReadBinaryData(cstate, (char *) &buf, sizeof(buf)) != sizeof(buf))
{
*val = 0; /* suppress compiler warning */
return false;
@ -754,7 +760,7 @@ CopyGetInt32(CopyState cstate, int32 *val)
/*
* CopySendInt16 sends an int16 in network byte order
*/
static void
static inline void
CopySendInt16(CopyState cstate, int16 val)
{
uint16 buf;
@ -766,12 +772,12 @@ CopySendInt16(CopyState cstate, int16 val)
/*
* CopyGetInt16 reads an int16 that appears in network byte order
*/
static bool
static inline bool
CopyGetInt16(CopyState cstate, int16 *val)
{
uint16 buf;
if (CopyGetData(cstate, &buf, sizeof(buf), sizeof(buf)) != sizeof(buf))
if (CopyReadBinaryData(cstate, (char *) &buf, sizeof(buf)) != sizeof(buf))
{
*val = 0; /* suppress compiler warning */
return false;
@ -786,26 +792,20 @@ CopyGetInt16(CopyState cstate, int16 *val)
*
* Returns true if able to obtain at least one more byte, else false.
*
* If raw_buf_index < raw_buf_len, the unprocessed bytes are transferred
* down to the start of the buffer and then we load more data after that.
* This case is used only when a frontend multibyte character crosses a
* bufferload boundary.
* If RAW_BUF_BYTES(cstate) > 0, the unprocessed bytes are moved to the start
* of the buffer and then we load more data after that. This case occurs only
* when a multibyte character crosses a bufferload boundary.
*/
static bool
CopyLoadRawBuf(CopyState cstate)
{
int nbytes;
int nbytes = RAW_BUF_BYTES(cstate);
int inbytes;
if (cstate->raw_buf_index < cstate->raw_buf_len)
{
/* Copy down the unprocessed data */
nbytes = cstate->raw_buf_len - cstate->raw_buf_index;
/* Copy down the unprocessed data if any. */
if (nbytes > 0)
memmove(cstate->raw_buf, cstate->raw_buf + cstate->raw_buf_index,
nbytes);
}
else
nbytes = 0; /* no data need be saved */
inbytes = CopyGetData(cstate, cstate->raw_buf + nbytes,
1, RAW_BUF_SIZE - nbytes);
@ -816,6 +816,54 @@ CopyLoadRawBuf(CopyState cstate)
return (inbytes > 0);
}
/*
* CopyReadBinaryData
*
* 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(CopyState cstate, char *dest, int nbytes)
{
int copied_bytes = 0;
if (RAW_BUF_BYTES(cstate) >= nbytes)
{
/* Enough bytes are present in the buffer. */
memcpy(dest, cstate->raw_buf + cstate->raw_buf_index, nbytes);
cstate->raw_buf_index += nbytes;
copied_bytes = nbytes;
}
else
{
/*
* Not enough bytes in the buffer, so must read from the file. Need
* to loop since 'nbytes' could be larger than the buffer size.
*/
do
{
int copy_bytes;
/* Load more data if buffer is empty. */
if (RAW_BUF_BYTES(cstate) == 0)
{
if (!CopyLoadRawBuf(cstate))
break; /* EOF */
}
/* Transfer some bytes. */
copy_bytes = Min(nbytes - copied_bytes, RAW_BUF_BYTES(cstate));
memcpy(dest, cstate->raw_buf + cstate->raw_buf_index, copy_bytes);
cstate->raw_buf_index += copy_bytes;
dest += copy_bytes;
copied_bytes += copy_bytes;
} while (copied_bytes < nbytes);
}
return copied_bytes;
}
/*
* DoCopy executes the SQL COPY statement
@ -3366,17 +3414,17 @@ BeginCopyFrom(ParseState *pstate,
cstate->cur_attval = NULL;
/*
* Set up variables to avoid per-attribute overhead. attribute_buf is
* used in both text and binary modes, but we use line_buf and raw_buf
* Set up variables to avoid per-attribute overhead. attribute_buf and
* raw_buf are used in both text and binary modes, but we use line_buf
* only in text mode.
*/
initStringInfo(&cstate->attribute_buf);
cstate->raw_buf = (char *) palloc(RAW_BUF_SIZE + 1);
cstate->raw_buf_index = cstate->raw_buf_len = 0;
if (!cstate->binary)
{
initStringInfo(&cstate->line_buf);
cstate->line_buf_converted = false;
cstate->raw_buf = (char *) palloc(RAW_BUF_SIZE + 1);
cstate->raw_buf_index = cstate->raw_buf_len = 0;
}
/* Assign range table, we'll need it in CopyFrom. */
@ -3527,7 +3575,7 @@ BeginCopyFrom(ParseState *pstate,
int32 tmp;
/* Signature */
if (CopyGetData(cstate, readSig, 11, 11) != 11 ||
if (CopyReadBinaryData(cstate, readSig, 11) != 11 ||
memcmp(readSig, BinarySignature, 11) != 0)
ereport(ERROR,
(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
@ -3555,7 +3603,7 @@ BeginCopyFrom(ParseState *pstate,
/* Skip extension header, if present */
while (tmp-- > 0)
{
if (CopyGetData(cstate, readSig, 1, 1) != 1)
if (CopyReadBinaryData(cstate, readSig, 1) != 1)
ereport(ERROR,
(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
errmsg("invalid COPY file header (wrong length)")));
@ -3771,7 +3819,7 @@ NextCopyFrom(CopyState cstate, ExprContext *econtext,
char dummy;
if (cstate->copy_dest != COPY_OLD_FE &&
CopyGetData(cstate, &dummy, 1, 1) > 0)
CopyReadBinaryData(cstate, &dummy, 1) > 0)
ereport(ERROR,
(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
errmsg("received copy data after EOF marker")));
@ -4744,8 +4792,8 @@ CopyReadBinaryAttribute(CopyState cstate, FmgrInfo *flinfo,
resetStringInfo(&cstate->attribute_buf);
enlargeStringInfo(&cstate->attribute_buf, fld_size);
if (CopyGetData(cstate, cstate->attribute_buf.data,
fld_size, fld_size) != fld_size)
if (CopyReadBinaryData(cstate, cstate->attribute_buf.data,
fld_size) != fld_size)
ereport(ERROR,
(errcode(ERRCODE_BAD_COPY_FILE_FORMAT),
errmsg("unexpected EOF in COPY data")));