/* ----------
* toast_compress_datum -
*
* Create a compressed version of a varlena datum
*
* If we fail (ie, compressed result is actually bigger than original)
* then return NULL. We must not use compressed data if it'd expand
* the tuple!
*
* We use VAR{SIZE,DATA}_ANY so we can handle short varlenas here without
* copying them. But we can't handle external or compressed datums.
* ----------
*/
Datum
toast_compress_datum(Datum value)
{
varattrib *tmp;
int32 valsize = VARSIZE_ANY_EXHDR_D(value);
Assert(!VARATT_IS_EXTERNAL(DatumGetPointer(value)));
Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
/*
* No point in wasting a palloc cycle if value size is out of the allowed
* range for compression
*/
if (valsize < PGLZ_strategy_default->min_input_size ||
valsize > PGLZ_strategy_default->max_input_size)
return PointerGetDatum(NULL);
tmp = (varattrib *) palloc(PGLZ_MAX_OUTPUT(valsize));
if (pglz_compress(VARDATA_ANY_D(value), valsize,
(PGLZ_Header *) tmp, PGLZ_strategy_default) &&
VARSIZE(tmp) < VARSIZE_ANY_D(value))
{
/* successful compression */
VARATT_SET_COMPRESSED(tmp);
return PointerGetDatum(tmp);
}
else
{
/* incompressible data */
pfree(tmp);
return PointerGetDatum(NULL);
}
}
/* ----------
* toast_compress_datum -
*
* Create a compressed version of a varlena datum
*
* If we fail (ie, compressed result is actually bigger than original)
* then return NULL. We must not use compressed data if it'd expand
* the tuple!
*
* We use VAR{SIZE,DATA}_ANY so we can handle short varlenas here without
* copying them. But we can't handle external or compressed datums.
* ----------
*/
Datum
toast_compress_datum(Datum value)
{
struct varlena *tmp;
int32 valsize = VARSIZE_ANY_EXHDR(DatumGetPointer(value));
Assert(!VARATT_IS_EXTERNAL(DatumGetPointer(value)));
Assert(!VARATT_IS_COMPRESSED(DatumGetPointer(value)));
/*
* No point in wasting a palloc cycle if value size is out of the allowed
* range for compression
*/
if (valsize < PGLZ_strategy_default->min_input_size ||
valsize > PGLZ_strategy_default->max_input_size)
return PointerGetDatum(NULL);
tmp = (struct varlena *) palloc(PGLZ_MAX_OUTPUT(valsize));
/*
* We recheck the actual size even if pglz_compress() reports success,
* because it might be satisfied with having saved as little as one byte
* in the compressed data --- which could turn into a net loss once you
* consider header and alignment padding. Worst case, the compressed
* format might require three padding bytes (plus header, which is
* included in VARSIZE(tmp)), whereas the uncompressed format would take
* only one header byte and no padding if the value is short enough. So
* we insist on a savings of more than 2 bytes to ensure we have a gain.
*/
if (pglz_compress(VARDATA_ANY(DatumGetPointer(value)), valsize,
(PGLZ_Header *) tmp, PGLZ_strategy_default) &&
VARSIZE(tmp) < valsize - 2)
{
/* successful compression */
return PointerGetDatum(tmp);
}
else
{
/* incompressible data */
pfree(tmp);
return PointerGetDatum(NULL);
}
}
/*
* compress_data
*
* Compress the bytea buffer and return the result as bytea.
*/
Datum
compress_data(PG_FUNCTION_ARGS)
{
bytea *raw_data = PG_GETARG_BYTEA_P(0);
bytea *res;
int32 compressed_len;
char *compressed_data;
PGLZ_Strategy strategy;
memcpy(&strategy, (PGLZ_Strategy *) PGLZ_strategy_always,
sizeof(PGLZ_Strategy));
/* Get custom values if specified by user */
if (PG_NARGS() == 7)
{
strategy.min_input_size = PG_GETARG_INT32(1);
strategy.max_input_size = PG_GETARG_INT32(2);
strategy.min_comp_rate = PG_GETARG_INT32(3);
strategy.first_success_by = PG_GETARG_INT32(4);
strategy.match_size_good = PG_GETARG_INT32(5);
strategy.match_size_drop = PG_GETARG_INT32(6);
}
/* Compress data in build */
compressed_data = palloc(PGLZ_MAX_OUTPUT(VARSIZE(raw_data) - VARHDRSZ));
compressed_len = pglz_compress(VARDATA(raw_data),
VARSIZE(raw_data) - VARHDRSZ,
compressed_data,
&strategy);
/* if compression failed return the original data */
if (compressed_len < 0)
PG_RETURN_BYTEA_P(raw_data);
/* Build result */
res = (bytea *) palloc(VARHDRSZ + compressed_len);
SET_VARSIZE(res, compressed_len + VARHDRSZ);
memcpy(VARDATA(res), compressed_data, compressed_len);
pfree(compressed_data);
PG_RETURN_BYTEA_P(res);
}
/* ----------
* toast_compress_datum -
*
* Create a compressed version of a varlena datum
*
* If we fail (ie, compressed result is actually bigger than original)
* then return NULL. We must not use compressed data if it'd expand
* the tuple!
* ----------
*/
Datum
toast_compress_datum(Datum value)
{
varattrib *tmp;
int32 valsize = VARATT_SIZE(value) - VARHDRSZ;
tmp = (varattrib *) palloc(PGLZ_MAX_OUTPUT(valsize));
if (pglz_compress(VARATT_DATA(value), valsize,
(PGLZ_Header *) tmp, PGLZ_strategy_default) &&
VARATT_SIZE(tmp) < VARATT_SIZE(value))
{
/* successful compression */
VARATT_SIZEP(tmp) |= VARATT_FLAG_COMPRESSED;
return PointerGetDatum(tmp);
}
else
{
/* incompressible data */
pfree(tmp);
return PointerGetDatum(NULL);
}
}
/*
* SerializeBlockData serializes and compresses block data at given block index with given
* compression type for every column.
*/
static void
SerializeBlockData(TableWriteState *writeState, uint32 blockIndex, uint32 rowCount)
{
uint32 columnIndex = 0;
StripeBuffers *stripeBuffers = writeState->stripeBuffers;
ColumnBlockData **blockDataArray = writeState->blockDataArray;
CompressionType requestedCompressionType = writeState->compressionType;
const uint32 columnCount = stripeBuffers->columnCount;
StringInfo compressionBuffer = writeState->compressionBuffer;
/* serialize exist values, data values are already serialized */
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
ColumnBuffers *columnBuffers = stripeBuffers->columnBuffersArray[columnIndex];
ColumnBlockBuffers *blockBuffers = columnBuffers->blockBuffersArray[blockIndex];
ColumnBlockData *blockData = blockDataArray[columnIndex];
blockBuffers->existsBuffer = SerializeBoolArray(blockData->existsArray, rowCount);
}
/*
* check and compress value buffers, if a value buffer is not compressable
* then keep it as uncompressed, store compression information.
*/
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
uint64 maximumLength = 0;
bool compressable = false;
ColumnBuffers *columnBuffers = stripeBuffers->columnBuffersArray[columnIndex];
ColumnBlockBuffers *blockBuffers = columnBuffers->blockBuffersArray[blockIndex];
ColumnBlockData *blockData = blockDataArray[columnIndex];
StringInfo serializedValueBuffer = NULL;
CompressionType actualCompressionType = COMPRESSION_NONE;
serializedValueBuffer = blockData->valueBuffer;
/* the only other supported compression type is pg_lz for now */
Assert(requestedCompressionType == COMPRESSION_NONE ||
requestedCompressionType == COMPRESSION_PG_LZ);
/*
* if serializedValueBuffer is be compressed, update serializedValueBuffer
* with compressed data and store compression type.
*/
if (requestedCompressionType == COMPRESSION_PG_LZ)
{
maximumLength = PGLZ_MAX_OUTPUT(serializedValueBuffer->len);
resetStringInfo(compressionBuffer);
enlargeStringInfo(compressionBuffer, maximumLength);
compressable = cstore_pglz_compress((const char *) serializedValueBuffer->data,
serializedValueBuffer->len,
(PGLZ_Header*)compressionBuffer->data,
PGLZ_strategy_always);
if (compressable)
{
serializedValueBuffer = compressionBuffer;
serializedValueBuffer->len = VARSIZE(compressionBuffer->data);
actualCompressionType = COMPRESSION_PG_LZ;
}
}
/* store (compressed) value buffer */
blockBuffers->valueCompressionType = actualCompressionType;
blockBuffers->valueBuffer = CopyStringInfo(serializedValueBuffer);
/* valueBuffer needs to be reset for next block's data */
resetStringInfo(blockData->valueBuffer);
}
}
/*
* FlushStripe compresses the data in the current stripe, flushes the compressed
* data into the file, and returns the stripe metadata. To do this, the function
* first creates the data buffers, and then updates position and length statistics
* in stripe's skip list. Then, the function creates the skip list and footer
* buffers. Finally, the function flushes the skip list, data, and footer buffers
* to the file.
*/
static StripeMetadata
FlushStripe(TableWriteState *writeState)
{
StripeMetadata stripeMetadata = {0, 0, 0, 0};
uint64 skipListLength = 0;
uint64 dataLength = 0;
StringInfo **existsBufferArray = NULL;
StringInfo **valueBufferArray = NULL;
CompressionType **valueCompressionTypeArray = NULL;
StringInfo *skipListBufferArray = NULL;
StripeFooter *stripeFooter = NULL;
StringInfo stripeFooterBuffer = NULL;
uint32 columnIndex = 0;
uint32 blockIndex = 0;
FILE *tableFile = writeState->tableFile;
StripeData *stripeData = writeState->stripeData;
StripeSkipList *stripeSkipList = writeState->stripeSkipList;
CompressionType compressionType = writeState->compressionType;
TupleDesc tupleDescriptor = writeState->tupleDescriptor;
uint32 columnCount = tupleDescriptor->natts;
uint32 blockCount = stripeSkipList->blockCount;
/* create "exists" and "value" buffers */
existsBufferArray = CreateExistsBufferArray(stripeData->columnDataArray,
stripeSkipList);
valueBufferArray = CreateValueBufferArray(stripeData->columnDataArray,
stripeSkipList, tupleDescriptor);
valueCompressionTypeArray = palloc0(columnCount * sizeof(CompressionType *));
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
CompressionType *blockCompressionTypeArray =
palloc0(blockCount * sizeof(CompressionType));
valueCompressionTypeArray[columnIndex] = blockCompressionTypeArray;
for (blockIndex = 0; blockIndex < blockCount; blockIndex++)
{
StringInfo valueBuffer = NULL;
uint64 maximumLength = 0;
PGLZ_Header *compressedData = NULL;
bool compressable = false;
if (compressionType == COMPRESSION_NONE)
{
blockCompressionTypeArray[blockIndex] = COMPRESSION_NONE;
continue;
}
/* the only other supported compression type is pg_lz for now */
Assert(compressionType == COMPRESSION_PG_LZ);
valueBuffer = valueBufferArray[columnIndex][blockIndex];
maximumLength = PGLZ_MAX_OUTPUT(valueBuffer->len);
compressedData = palloc0(maximumLength);
compressable = pglz_compress((const char *) valueBuffer->data,
valueBuffer->len, compressedData,
PGLZ_strategy_always);
if (compressable)
{
pfree(valueBuffer->data);
valueBuffer->data = (char *) compressedData;
valueBuffer->len = VARSIZE(compressedData);
valueBuffer->maxlen = maximumLength;
blockCompressionTypeArray[blockIndex] = COMPRESSION_PG_LZ;
}
else
{
pfree(compressedData);
blockCompressionTypeArray[blockIndex] = COMPRESSION_NONE;
}
}
}
/* update buffer sizes and positions in stripe skip list */
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
ColumnBlockSkipNode **columnSkipNodeArray = stripeSkipList->blockSkipNodeArray;
ColumnBlockSkipNode *blockSkipNodeArray = columnSkipNodeArray[columnIndex];
uint32 blockCount = stripeSkipList->blockCount;
uint32 blockIndex = 0;
uint64 currentExistsBlockOffset = 0;
uint64 currentValueBlockOffset = 0;
for (blockIndex = 0; blockIndex < blockCount; blockIndex++)
{
uint64 existsBufferSize = existsBufferArray[columnIndex][blockIndex]->len;
uint64 valueBufferSize = valueBufferArray[columnIndex][blockIndex]->len;
CompressionType valueCompressionType =
valueCompressionTypeArray[columnIndex][blockIndex];
ColumnBlockSkipNode *blockSkipNode = &blockSkipNodeArray[blockIndex];
blockSkipNode->existsBlockOffset = currentExistsBlockOffset;
blockSkipNode->existsLength = existsBufferSize;
blockSkipNode->valueBlockOffset = currentValueBlockOffset;
blockSkipNode->valueLength = valueBufferSize;
blockSkipNode->valueCompressionType = valueCompressionType;
currentExistsBlockOffset += existsBufferSize;
currentValueBlockOffset += valueBufferSize;
}
}
/* create skip list and footer buffers */
skipListBufferArray = CreateSkipListBufferArray(stripeSkipList, tupleDescriptor);
stripeFooter = CreateStripeFooter(stripeSkipList, skipListBufferArray);
stripeFooterBuffer = SerializeStripeFooter(stripeFooter);
/*
* Each stripe has three sections:
* (1) Skip list, which contains statistics for each column block, and can
* be used to skip reading row blocks that are refuted by WHERE clause list,
* (2) Data section, in which we store data for each column continuously.
* We store data for each for each column in blocks. For each block, we
* store two buffers: "exists" buffer, and "value" buffer. "exists" buffer
* tells which values are not NULL. "value" buffer contains values for
* present values. For each column, we first store all "exists" buffers,
* and then all "value" buffers.
* (3) Stripe footer, which contains the skip list buffer size, exists buffer
* size, and value buffer size for each of the columns.
*
* We start by flushing the skip list buffers.
*/
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
StringInfo skipListBuffer = skipListBufferArray[columnIndex];
WriteToFile(tableFile, skipListBuffer->data, skipListBuffer->len);
}
/* then, we flush the data buffers */
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
uint32 blockIndex = 0;
for (blockIndex = 0; blockIndex < stripeSkipList->blockCount; blockIndex++)
{
StringInfo existsBuffer = existsBufferArray[columnIndex][blockIndex];
WriteToFile(tableFile, existsBuffer->data, existsBuffer->len);
}
for (blockIndex = 0; blockIndex < stripeSkipList->blockCount; blockIndex++)
{
StringInfo valueBuffer = valueBufferArray[columnIndex][blockIndex];
WriteToFile(tableFile, valueBuffer->data, valueBuffer->len);
}
}
/* finally, we flush the footer buffer */
WriteToFile(tableFile, stripeFooterBuffer->data, stripeFooterBuffer->len);
/* set stripe metadata */
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
skipListLength += stripeFooter->skipListSizeArray[columnIndex];
dataLength += stripeFooter->existsSizeArray[columnIndex];
dataLength += stripeFooter->valueSizeArray[columnIndex];
}
stripeMetadata.fileOffset = writeState->currentFileOffset;
stripeMetadata.skipListLength = skipListLength;
stripeMetadata.dataLength = dataLength;
stripeMetadata.footerLength = stripeFooterBuffer->len;
/* advance current file offset */
writeState->currentFileOffset += skipListLength;
writeState->currentFileOffset += dataLength;
writeState->currentFileOffset += stripeFooterBuffer->len;
return stripeMetadata;
}