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cstore_reader.c
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cstore_reader.c
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/*-------------------------------------------------------------------------
*
* cstore_reader.c
*
* This file contains function definitions for reading cstore files. This
* includes the logic for reading file level metadata, reading row stripes,
* and skipping unrelated row blocks and columns.
*
* Copyright (c) 2016, Citus Data, Inc.
*
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "cstore_fdw.h"
#include "cstore_metadata_serialization.h"
#include "cstore_version_compat.h"
#include "access/nbtree.h"
#include "access/skey.h"
#include "commands/defrem.h"
#include "nodes/makefuncs.h"
#if PG_VERSION_NUM >= 120000
#include "nodes/pathnodes.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#else
#include "optimizer/clauses.h"
#include "optimizer/predtest.h"
#include "optimizer/var.h"
#endif
#include "optimizer/restrictinfo.h"
#include "port.h"
#include "storage/fd.h"
#include "utils/memutils.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
/* static function declarations */
static StripeBuffers * LoadFilteredStripeBuffers(FILE *tableFile,
StripeMetadata *stripeMetadata,
TupleDesc tupleDescriptor,
List *projectedColumnList,
List *whereClauseList);
static void ReadStripeNextRow(StripeBuffers *stripeBuffers, List *projectedColumnList,
uint64 blockIndex, uint64 blockRowIndex,
ColumnBlockData **blockDataArray,
Datum *columnValues, bool *columnNulls);
static ColumnBuffers * LoadColumnBuffers(FILE *tableFile,
ColumnBlockSkipNode *blockSkipNodeArray,
uint32 blockCount, uint64 existsFileOffset,
uint64 valueFileOffset,
Form_pg_attribute attributeForm);
static StripeFooter * LoadStripeFooter(FILE *tableFile, StripeMetadata *stripeMetadata,
uint32 columnCount);
static StripeSkipList * LoadStripeSkipList(FILE *tableFile,
StripeMetadata *stripeMetadata,
StripeFooter *stripeFooter,
uint32 columnCount,
bool *projectedColumnMask,
TupleDesc tupleDescriptor);
static bool * SelectedBlockMask(StripeSkipList *stripeSkipList,
List *projectedColumnList, List *whereClauseList);
static List * BuildRestrictInfoList(List *whereClauseList);
static Node * BuildBaseConstraint(Var *variable);
static OpExpr * MakeOpExpression(Var *variable, int16 strategyNumber);
static Oid GetOperatorByType(Oid typeId, Oid accessMethodId, int16 strategyNumber);
static void UpdateConstraint(Node *baseConstraint, Datum minValue, Datum maxValue);
static StripeSkipList * SelectedBlockSkipList(StripeSkipList *stripeSkipList,
bool *projectedColumnMask,
bool *selectedBlockMask);
static uint32 StripeSkipListRowCount(StripeSkipList *stripeSkipList);
static bool * ProjectedColumnMask(uint32 columnCount, List *projectedColumnList);
static void DeserializeBoolArray(StringInfo boolArrayBuffer, bool *boolArray,
uint32 boolArrayLength);
static void DeserializeDatumArray(StringInfo datumBuffer, bool *existsArray,
uint32 datumCount, bool datumTypeByValue,
int datumTypeLength, char datumTypeAlign,
Datum *datumArray);
static void DeserializeBlockData(StripeBuffers *stripeBuffers, uint64 blockIndex,
uint32 rowCount, ColumnBlockData **blockDataArray,
TupleDesc tupleDescriptor);
static Datum ColumnDefaultValue(TupleConstr *tupleConstraints,
Form_pg_attribute attributeForm);
static int64 FILESize(FILE *file);
static StringInfo ReadFromFile(FILE *file, uint64 offset, uint32 size);
static void ResetUncompressedBlockData(ColumnBlockData **blockDataArray,
uint32 columnCount);
static uint64 StripeRowCount(FILE *tableFile, StripeMetadata *stripeMetadata);
/*
* CStoreBeginRead initializes a cstore read operation. This function returns a
* read handle that's used during reading rows and finishing the read operation.
*/
TableReadState *
CStoreBeginRead(const char *filename, TupleDesc tupleDescriptor,
List *projectedColumnList, List *whereClauseList)
{
TableReadState *readState = NULL;
TableFooter *tableFooter = NULL;
FILE *tableFile = NULL;
MemoryContext stripeReadContext = NULL;
uint32 columnCount = 0;
bool *projectedColumnMask = NULL;
ColumnBlockData **blockDataArray = NULL;
StringInfo tableFooterFilename = makeStringInfo();
appendStringInfo(tableFooterFilename, "%s%s", filename, CSTORE_FOOTER_FILE_SUFFIX);
tableFooter = CStoreReadFooter(tableFooterFilename);
pfree(tableFooterFilename->data);
pfree(tableFooterFilename);
tableFile = AllocateFile(filename, PG_BINARY_R);
if (tableFile == NULL)
{
ereport(ERROR, (errcode_for_file_access(),
errmsg("could not open file \"%s\" for reading: %m",
filename)));
}
/*
* We allocate all stripe specific data in the stripeReadContext, and reset
* this memory context before loading a new stripe. This is to avoid memory
* leaks.
*/
stripeReadContext = AllocSetContextCreate(CurrentMemoryContext,
"Stripe Read Memory Context",
ALLOCSET_DEFAULT_SIZES);
columnCount = tupleDescriptor->natts;
projectedColumnMask = ProjectedColumnMask(columnCount, projectedColumnList);
blockDataArray = CreateEmptyBlockDataArray(columnCount, projectedColumnMask,
tableFooter->blockRowCount);
readState = palloc0(sizeof(TableReadState));
readState->tableFile = tableFile;
readState->tableFooter = tableFooter;
readState->projectedColumnList = projectedColumnList;
readState->whereClauseList = whereClauseList;
readState->stripeBuffers = NULL;
readState->readStripeCount = 0;
readState->stripeReadRowCount = 0;
readState->tupleDescriptor = tupleDescriptor;
readState->stripeReadContext = stripeReadContext;
readState->blockDataArray = blockDataArray;
readState->deserializedBlockIndex = -1;
return readState;
}
/*
* CStoreReadFooter reads the cstore file footer from the given file. First, the
* function reads the last byte of the file as the postscript size. Then, the
* function reads the postscript. Last, the function reads and deserializes the
* footer.
*/
TableFooter *
CStoreReadFooter(StringInfo tableFooterFilename)
{
TableFooter *tableFooter = NULL;
FILE *tableFooterFile = NULL;
uint64 footerOffset = 0;
uint64 footerLength = 0;
StringInfo postscriptBuffer = NULL;
StringInfo postscriptSizeBuffer = NULL;
uint64 postscriptSizeOffset = 0;
uint8 postscriptSize = 0;
uint64 footerFileSize = 0;
uint64 postscriptOffset = 0;
StringInfo footerBuffer = NULL;
int freeResult = 0;
tableFooterFile = AllocateFile(tableFooterFilename->data, PG_BINARY_R);
if (tableFooterFile == NULL)
{
ereport(ERROR, (errcode_for_file_access(),
errmsg("could not open file \"%s\" for reading: %m",
tableFooterFilename->data),
errhint("Try copying in data to the table.")));
}
footerFileSize = FILESize(tableFooterFile);
if (footerFileSize < CSTORE_POSTSCRIPT_SIZE_LENGTH)
{
ereport(ERROR, (errmsg("invalid cstore file")));
}
postscriptSizeOffset = footerFileSize - CSTORE_POSTSCRIPT_SIZE_LENGTH;
postscriptSizeBuffer = ReadFromFile(tableFooterFile, postscriptSizeOffset,
CSTORE_POSTSCRIPT_SIZE_LENGTH);
memcpy(&postscriptSize, postscriptSizeBuffer->data, CSTORE_POSTSCRIPT_SIZE_LENGTH);
if (postscriptSize + CSTORE_POSTSCRIPT_SIZE_LENGTH > footerFileSize)
{
ereport(ERROR, (errmsg("invalid postscript size")));
}
postscriptOffset = footerFileSize - (CSTORE_POSTSCRIPT_SIZE_LENGTH + postscriptSize);
postscriptBuffer = ReadFromFile(tableFooterFile, postscriptOffset, postscriptSize);
DeserializePostScript(postscriptBuffer, &footerLength);
if (footerLength + postscriptSize + CSTORE_POSTSCRIPT_SIZE_LENGTH > footerFileSize)
{
ereport(ERROR, (errmsg("invalid footer size")));
}
footerOffset = postscriptOffset - footerLength;
footerBuffer = ReadFromFile(tableFooterFile, footerOffset, footerLength);
tableFooter = DeserializeTableFooter(footerBuffer);
freeResult = FreeFile(tableFooterFile);
if (freeResult != 0)
{
ereport(ERROR, (errcode_for_file_access(),
errmsg("could not close file: %m")));
}
return tableFooter;
}
/*
* CStoreReadNextRow tries to read a row from the cstore file. On success, it sets
* column values and nulls, and returns true. If there are no more rows to read,
* the function returns false.
*/
bool
CStoreReadNextRow(TableReadState *readState, Datum *columnValues, bool *columnNulls)
{
uint32 blockIndex = 0;
uint32 blockRowIndex = 0;
TableFooter *tableFooter = readState->tableFooter;
MemoryContext oldContext = NULL;
/*
* If no stripes are loaded, load the next non-empty stripe. Note that when
* loading stripes, we skip over blocks whose contents can be filtered with
* the query's restriction qualifiers. So, even when a stripe is physically
* not empty, we may end up loading it as an empty stripe.
*/
while (readState->stripeBuffers == NULL)
{
StripeBuffers *stripeBuffers = NULL;
StripeMetadata *stripeMetadata = NULL;
List *stripeMetadataList = tableFooter->stripeMetadataList;
uint32 stripeCount = list_length(stripeMetadataList);
/* if we have read all stripes, return false */
if (readState->readStripeCount == stripeCount)
{
return false;
}
oldContext = MemoryContextSwitchTo(readState->stripeReadContext);
MemoryContextReset(readState->stripeReadContext);
stripeMetadata = list_nth(stripeMetadataList, readState->readStripeCount);
stripeBuffers = LoadFilteredStripeBuffers(readState->tableFile, stripeMetadata,
readState->tupleDescriptor,
readState->projectedColumnList,
readState->whereClauseList);
readState->readStripeCount++;
MemoryContextSwitchTo(oldContext);
if (stripeBuffers->rowCount != 0)
{
readState->stripeBuffers = stripeBuffers;
readState->stripeReadRowCount = 0;
readState->deserializedBlockIndex = -1;
ResetUncompressedBlockData(readState->blockDataArray,
stripeBuffers->columnCount);
break;
}
}
blockIndex = readState->stripeReadRowCount / tableFooter->blockRowCount;
blockRowIndex = readState->stripeReadRowCount % tableFooter->blockRowCount;
if (blockIndex != readState->deserializedBlockIndex)
{
uint32 lastBlockIndex = 0;
uint32 blockRowCount = 0;
uint32 stripeRowCount = 0;
stripeRowCount = readState->stripeBuffers->rowCount;
lastBlockIndex = stripeRowCount / tableFooter->blockRowCount;
if (blockIndex == lastBlockIndex)
{
blockRowCount = stripeRowCount % tableFooter->blockRowCount;
}
else
{
blockRowCount = tableFooter->blockRowCount;
}
oldContext = MemoryContextSwitchTo(readState->stripeReadContext);
DeserializeBlockData(readState->stripeBuffers, blockIndex,
blockRowCount, readState->blockDataArray,
readState->tupleDescriptor);
MemoryContextSwitchTo(oldContext);
readState->deserializedBlockIndex = blockIndex;
}
ReadStripeNextRow(readState->stripeBuffers, readState->projectedColumnList,
blockIndex, blockRowIndex, readState->blockDataArray,
columnValues, columnNulls);
/*
* If we finished reading the current stripe, set stripe data to NULL. That
* way, we will load a new stripe the next time this function gets called.
*/
readState->stripeReadRowCount++;
if (readState->stripeReadRowCount == readState->stripeBuffers->rowCount)
{
readState->stripeBuffers = NULL;
}
return true;
}
/* Finishes a cstore read operation. */
void
CStoreEndRead(TableReadState *readState)
{
int columnCount = readState->tupleDescriptor->natts;
MemoryContextDelete(readState->stripeReadContext);
FreeFile(readState->tableFile);
list_free_deep(readState->tableFooter->stripeMetadataList);
FreeColumnBlockDataArray(readState->blockDataArray, columnCount);
pfree(readState->tableFooter);
pfree(readState);
}
/*
* CreateEmptyBlockDataArray creates data buffers to keep deserialized exist and
* value arrays for requested columns in columnMask.
*/
ColumnBlockData **
CreateEmptyBlockDataArray(uint32 columnCount, bool *columnMask, uint32 blockRowCount)
{
uint32 columnIndex = 0;
ColumnBlockData **blockDataArray = palloc0(columnCount * sizeof(ColumnBlockData*));
/* allocate block memory for deserialized data */
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
if (columnMask[columnIndex])
{
ColumnBlockData *blockData = palloc0(sizeof(ColumnBlockData));
blockData->existsArray = palloc0(blockRowCount * sizeof(bool));
blockData->valueArray = palloc0(blockRowCount * sizeof(Datum));
blockData->valueBuffer = NULL;
blockDataArray[columnIndex] = blockData;
}
}
return blockDataArray;
}
/*
* FreeColumnBlockDataArray deallocates data buffers to keep deserialized exist and
* value arrays for requested columns in columnMask.
* ColumnBlockData->serializedValueBuffer lives in memory read/write context
* so it is deallocated automatically when the context is deleted.
*/
void
FreeColumnBlockDataArray(ColumnBlockData **blockDataArray, uint32 columnCount)
{
uint32 columnIndex = 0;
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
ColumnBlockData *blockData = blockDataArray[columnIndex];
if (blockData != NULL)
{
pfree(blockData->existsArray);
pfree(blockData->valueArray);
pfree(blockData);
}
}
pfree(blockDataArray);
}
/* CStoreTableRowCount returns the exact row count of a table using skiplists */
uint64
CStoreTableRowCount(const char *filename)
{
TableFooter *tableFooter = NULL;
FILE *tableFile;
ListCell *stripeMetadataCell = NULL;
uint64 totalRowCount = 0;
StringInfo tableFooterFilename = makeStringInfo();
appendStringInfo(tableFooterFilename, "%s%s", filename, CSTORE_FOOTER_FILE_SUFFIX);
tableFooter = CStoreReadFooter(tableFooterFilename);
pfree(tableFooterFilename->data);
pfree(tableFooterFilename);
tableFile = AllocateFile(filename, PG_BINARY_R);
if (tableFile == NULL)
{
ereport(ERROR, (errcode_for_file_access(),
errmsg("could not open file \"%s\" for reading: %m", filename)));
}
foreach(stripeMetadataCell, tableFooter->stripeMetadataList)
{
StripeMetadata *stripeMetadata = (StripeMetadata *) lfirst(stripeMetadataCell);
totalRowCount += StripeRowCount(tableFile, stripeMetadata);
}
FreeFile(tableFile);
return totalRowCount;
}
/*
* StripeRowCount reads serialized stripe footer, the first column's
* skip list, and returns number of rows for given stripe.
*/
static uint64
StripeRowCount(FILE *tableFile, StripeMetadata *stripeMetadata)
{
uint64 rowCount = 0;
StripeFooter *stripeFooter = NULL;
StringInfo footerBuffer = NULL;
StringInfo firstColumnSkipListBuffer = NULL;
uint64 footerOffset = 0;
footerOffset += stripeMetadata->fileOffset;
footerOffset += stripeMetadata->skipListLength;
footerOffset += stripeMetadata->dataLength;
footerBuffer = ReadFromFile(tableFile, footerOffset, stripeMetadata->footerLength);
stripeFooter = DeserializeStripeFooter(footerBuffer);
firstColumnSkipListBuffer = ReadFromFile(tableFile, stripeMetadata->fileOffset,
stripeFooter->skipListSizeArray[0]);
rowCount = DeserializeRowCount(firstColumnSkipListBuffer);
return rowCount;
}
/*
* LoadFilteredStripeBuffers reads serialized stripe data from the given file.
* The function skips over blocks whose rows are refuted by restriction qualifiers,
* and only loads columns that are projected in the query.
*/
static StripeBuffers *
LoadFilteredStripeBuffers(FILE *tableFile, StripeMetadata *stripeMetadata,
TupleDesc tupleDescriptor, List *projectedColumnList,
List *whereClauseList)
{
StripeBuffers *stripeBuffers = NULL;
ColumnBuffers **columnBuffersArray = NULL;
uint64 currentColumnFileOffset = 0;
uint32 columnIndex = 0;
uint32 columnCount = tupleDescriptor->natts;
StripeFooter *stripeFooter = LoadStripeFooter(tableFile, stripeMetadata,
columnCount);
bool *projectedColumnMask = ProjectedColumnMask(columnCount, projectedColumnList);
StripeSkipList *stripeSkipList = LoadStripeSkipList(tableFile, stripeMetadata,
stripeFooter, columnCount,
projectedColumnMask,
tupleDescriptor);
bool *selectedBlockMask = SelectedBlockMask(stripeSkipList, projectedColumnList,
whereClauseList);
StripeSkipList *selectedBlockSkipList =
SelectedBlockSkipList(stripeSkipList, projectedColumnMask,
selectedBlockMask);
/* load column data for projected columns */
columnBuffersArray = palloc0(columnCount * sizeof(ColumnBuffers *));
currentColumnFileOffset = stripeMetadata->fileOffset + stripeMetadata->skipListLength;
for (columnIndex = 0; columnIndex < stripeFooter->columnCount; columnIndex++)
{
uint64 existsSize = stripeFooter->existsSizeArray[columnIndex];
uint64 valueSize = stripeFooter->valueSizeArray[columnIndex];
uint64 existsFileOffset = currentColumnFileOffset;
uint64 valueFileOffset = currentColumnFileOffset + existsSize;
if (projectedColumnMask[columnIndex])
{
ColumnBlockSkipNode *blockSkipNode =
selectedBlockSkipList->blockSkipNodeArray[columnIndex];
Form_pg_attribute attributeForm = TupleDescAttr(tupleDescriptor, columnIndex);
uint32 blockCount = selectedBlockSkipList->blockCount;
ColumnBuffers *columnBuffers = LoadColumnBuffers(tableFile, blockSkipNode,
blockCount,
existsFileOffset,
valueFileOffset,
attributeForm);
columnBuffersArray[columnIndex] = columnBuffers;
}
currentColumnFileOffset += existsSize;
currentColumnFileOffset += valueSize;
}
stripeBuffers = palloc0(sizeof(StripeBuffers));
stripeBuffers->columnCount = columnCount;
stripeBuffers->rowCount = StripeSkipListRowCount(selectedBlockSkipList);
stripeBuffers->columnBuffersArray = columnBuffersArray;
return stripeBuffers;
}
/*
* ReadStripeNextRow reads the next row from the given stripe, finds the projected
* column values within this row, and accordingly sets the column values and nulls.
* Note that this function sets the values for all non-projected columns to null.
*/
static void
ReadStripeNextRow(StripeBuffers *stripeBuffers, List *projectedColumnList,
uint64 blockIndex, uint64 blockRowIndex,
ColumnBlockData **blockDataArray, Datum *columnValues,
bool *columnNulls)
{
ListCell *projectedColumnCell = NULL;
/* set all columns to null by default */
memset(columnNulls, 1, stripeBuffers->columnCount * sizeof(bool));
foreach(projectedColumnCell, projectedColumnList)
{
Var *projectedColumn = lfirst(projectedColumnCell);
uint32 projectedColumnIndex = projectedColumn->varattno - 1;
ColumnBlockData *blockData = blockDataArray[projectedColumnIndex];
if (blockData->existsArray[blockRowIndex])
{
columnValues[projectedColumnIndex] = blockData->valueArray[blockRowIndex];
columnNulls[projectedColumnIndex] = false;
}
}
}
/*
* LoadColumnBuffers reads serialized column data from the given file. These
* column data are laid out as sequential blocks in the file; and block positions
* and lengths are retrieved from the column block skip node array.
*/
static ColumnBuffers *
LoadColumnBuffers(FILE *tableFile, ColumnBlockSkipNode *blockSkipNodeArray,
uint32 blockCount, uint64 existsFileOffset, uint64 valueFileOffset,
Form_pg_attribute attributeForm)
{
ColumnBuffers *columnBuffers = NULL;
uint32 blockIndex = 0;
ColumnBlockBuffers **blockBuffersArray =
palloc0(blockCount * sizeof(ColumnBlockBuffers *));
for (blockIndex = 0; blockIndex < blockCount; blockIndex++)
{
blockBuffersArray[blockIndex] = palloc0(sizeof(ColumnBlockBuffers));
}
/*
* We first read the "exists" blocks. We don't read "values" array here,
* because "exists" blocks are stored sequentially on disk, and we want to
* minimize disk seeks.
*/
for (blockIndex = 0; blockIndex < blockCount; blockIndex++)
{
ColumnBlockSkipNode *blockSkipNode = &blockSkipNodeArray[blockIndex];
uint64 existsOffset = existsFileOffset + blockSkipNode->existsBlockOffset;
StringInfo rawExistsBuffer = ReadFromFile(tableFile, existsOffset,
blockSkipNode->existsLength);
blockBuffersArray[blockIndex]->existsBuffer = rawExistsBuffer;
}
/* then read "values" blocks, which are also stored sequentially on disk */
for (blockIndex = 0; blockIndex < blockCount; blockIndex++)
{
ColumnBlockSkipNode *blockSkipNode = &blockSkipNodeArray[blockIndex];
CompressionType compressionType = blockSkipNode->valueCompressionType;
uint64 valueOffset = valueFileOffset + blockSkipNode->valueBlockOffset;
StringInfo rawValueBuffer = ReadFromFile(tableFile, valueOffset,
blockSkipNode->valueLength);
blockBuffersArray[blockIndex]->valueBuffer = rawValueBuffer;
blockBuffersArray[blockIndex]->valueCompressionType = compressionType;
}
columnBuffers = palloc0(sizeof(ColumnBuffers));
columnBuffers->blockBuffersArray = blockBuffersArray;
return columnBuffers;
}
/* Reads and returns the given stripe's footer. */
static StripeFooter *
LoadStripeFooter(FILE *tableFile, StripeMetadata *stripeMetadata,
uint32 columnCount)
{
StripeFooter *stripeFooter = NULL;
StringInfo footerBuffer = NULL;
uint64 footerOffset = 0;
footerOffset += stripeMetadata->fileOffset;
footerOffset += stripeMetadata->skipListLength;
footerOffset += stripeMetadata->dataLength;
footerBuffer = ReadFromFile(tableFile, footerOffset, stripeMetadata->footerLength);
stripeFooter = DeserializeStripeFooter(footerBuffer);
if (stripeFooter->columnCount > columnCount)
{
ereport(ERROR, (errmsg("stripe footer column count and table column count "
"don't match")));
}
return stripeFooter;
}
/* Reads the skip list for the given stripe. */
static StripeSkipList *
LoadStripeSkipList(FILE *tableFile, StripeMetadata *stripeMetadata,
StripeFooter *stripeFooter, uint32 columnCount,
bool *projectedColumnMask,
TupleDesc tupleDescriptor)
{
StripeSkipList *stripeSkipList = NULL;
ColumnBlockSkipNode **blockSkipNodeArray = NULL;
StringInfo firstColumnSkipListBuffer = NULL;
uint64 currentColumnSkipListFileOffset = 0;
uint32 columnIndex = 0;
uint32 stripeBlockCount = 0;
uint32 stripeColumnCount = stripeFooter->columnCount;
/* deserialize block count */
firstColumnSkipListBuffer = ReadFromFile(tableFile, stripeMetadata->fileOffset,
stripeFooter->skipListSizeArray[0]);
stripeBlockCount = DeserializeBlockCount(firstColumnSkipListBuffer);
/* deserialize column skip lists */
blockSkipNodeArray = palloc0(columnCount * sizeof(ColumnBlockSkipNode *));
currentColumnSkipListFileOffset = stripeMetadata->fileOffset;
for (columnIndex = 0; columnIndex < stripeColumnCount; columnIndex++)
{
uint64 columnSkipListSize = stripeFooter->skipListSizeArray[columnIndex];
bool firstColumn = columnIndex == 0;
/*
* Only selected columns' column skip lists are read. However, the first
* column's skip list is read regardless of being selected. It is used by
* StripeSkipListRowCount later.
*/
if (projectedColumnMask[columnIndex] || firstColumn)
{
Form_pg_attribute attributeForm = TupleDescAttr(tupleDescriptor, columnIndex);
StringInfo columnSkipListBuffer =
ReadFromFile(tableFile, currentColumnSkipListFileOffset,
columnSkipListSize);
ColumnBlockSkipNode *columnSkipList =
DeserializeColumnSkipList(columnSkipListBuffer, attributeForm->attbyval,
attributeForm->attlen, stripeBlockCount);
blockSkipNodeArray[columnIndex] = columnSkipList;
}
currentColumnSkipListFileOffset += columnSkipListSize;
}
/* table contains additional columns added after this stripe is created */
for (columnIndex = stripeColumnCount; columnIndex < columnCount; columnIndex++)
{
ColumnBlockSkipNode *columnSkipList = NULL;
uint32 blockIndex = 0;
bool firstColumn = columnIndex == 0;
/* no need to create ColumnBlockSkipList if the column is not selected */
if (!projectedColumnMask[columnIndex] && !firstColumn)
{
blockSkipNodeArray[columnIndex] = NULL;
continue;
}
/* create empty ColumnBlockSkipNode for missing columns*/
columnSkipList = palloc0(stripeBlockCount * sizeof(ColumnBlockSkipNode));
for (blockIndex = 0; blockIndex < stripeBlockCount; blockIndex++)
{
columnSkipList[blockIndex].rowCount = 0;
columnSkipList[blockIndex].hasMinMax = false;
columnSkipList[blockIndex].minimumValue = 0;
columnSkipList[blockIndex].maximumValue = 0;
columnSkipList[blockIndex].existsBlockOffset = 0;
columnSkipList[blockIndex].valueBlockOffset = 0;
columnSkipList[blockIndex].existsLength = 0;
columnSkipList[blockIndex].valueLength = 0;
columnSkipList[blockIndex].valueCompressionType = COMPRESSION_NONE;
}
blockSkipNodeArray[columnIndex] = columnSkipList;
}
stripeSkipList = palloc0(sizeof(StripeSkipList));
stripeSkipList->blockSkipNodeArray = blockSkipNodeArray;
stripeSkipList->columnCount = columnCount;
stripeSkipList->blockCount = stripeBlockCount;
return stripeSkipList;
}
/*
* SelectedBlockMask walks over each column's blocks and checks if a block can
* be filtered without reading its data. The filtering happens when all rows in
* the block can be refuted by the given qualifier conditions.
*/
static bool *
SelectedBlockMask(StripeSkipList *stripeSkipList, List *projectedColumnList,
List *whereClauseList)
{
bool *selectedBlockMask = NULL;
ListCell *columnCell = NULL;
uint32 blockIndex = 0;
List *restrictInfoList = BuildRestrictInfoList(whereClauseList);
selectedBlockMask = palloc0(stripeSkipList->blockCount * sizeof(bool));
memset(selectedBlockMask, true, stripeSkipList->blockCount * sizeof(bool));
foreach(columnCell, projectedColumnList)
{
Var *column = lfirst(columnCell);
uint32 columnIndex = column->varattno - 1;
FmgrInfo *comparisonFunction = NULL;
Node *baseConstraint = NULL;
/* if this column's data type doesn't have a comparator, skip it */
comparisonFunction = GetFunctionInfoOrNull(column->vartype, BTREE_AM_OID,
BTORDER_PROC);
if (comparisonFunction == NULL)
{
continue;
}
baseConstraint = BuildBaseConstraint(column);
for (blockIndex = 0; blockIndex < stripeSkipList->blockCount; blockIndex++)
{
bool predicateRefuted = false;
List *constraintList = NIL;
ColumnBlockSkipNode *blockSkipNodeArray =
stripeSkipList->blockSkipNodeArray[columnIndex];
ColumnBlockSkipNode *blockSkipNode = &blockSkipNodeArray[blockIndex];
/*
* A column block with comparable data type can miss min/max values
* if all values in the block are NULL.
*/
if (!blockSkipNode->hasMinMax)
{
continue;
}
UpdateConstraint(baseConstraint, blockSkipNode->minimumValue,
blockSkipNode->maximumValue);
constraintList = list_make1(baseConstraint);
#if (PG_VERSION_NUM >= 100000)
predicateRefuted = predicate_refuted_by(constraintList, restrictInfoList, false);
#else
predicateRefuted = predicate_refuted_by(constraintList, restrictInfoList);
#endif
if (predicateRefuted)
{
selectedBlockMask[blockIndex] = false;
}
}
}
return selectedBlockMask;
}
/*
* GetFunctionInfoOrNull first resolves the operator for the given data type,
* access method, and support procedure. The function then uses the resolved
* operator's identifier to fill in a function manager object, and returns
* this object. This function is based on a similar function from CitusDB's code.
*/
FmgrInfo *
GetFunctionInfoOrNull(Oid typeId, Oid accessMethodId, int16 procedureId)
{
FmgrInfo *functionInfo = NULL;
Oid operatorClassId = InvalidOid;
Oid operatorFamilyId = InvalidOid;
Oid operatorId = InvalidOid;
/* get default operator class from pg_opclass for datum type */
operatorClassId = GetDefaultOpClass(typeId, accessMethodId);
if (operatorClassId == InvalidOid)
{
return NULL;
}
operatorFamilyId = get_opclass_family(operatorClassId);
if (operatorFamilyId == InvalidOid)
{
return NULL;
}
operatorId = get_opfamily_proc(operatorFamilyId, typeId, typeId, procedureId);
if (operatorId != InvalidOid)
{
functionInfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo));
/* fill in the FmgrInfo struct using the operatorId */
fmgr_info(operatorId, functionInfo);
}
return functionInfo;
}
/*
* BuildRestrictInfoList builds restrict info list using the selection criteria,
* and then return this list. The function is copied from CitusDB's shard pruning
* logic.
*/
static List *
BuildRestrictInfoList(List *whereClauseList)
{
List *restrictInfoList = NIL;
ListCell *qualCell = NULL;
foreach(qualCell, whereClauseList)
{
RestrictInfo *restrictInfo = NULL;
Node *qualNode = (Node *) lfirst(qualCell);
restrictInfo = make_simple_restrictinfo((Expr *) qualNode);
restrictInfoList = lappend(restrictInfoList, restrictInfo);
}
return restrictInfoList;
}
/*
* BuildBaseConstraint builds and returns a base constraint. This constraint
* implements an expression in the form of (var <= max && var >= min), where
* min and max values represent a block's min and max values. These block
* values are filled in after the constraint is built. This function is based
* on a similar function from CitusDB's shard pruning logic.
*/
static Node *
BuildBaseConstraint(Var *variable)
{
Node *baseConstraint = NULL;
OpExpr *lessThanExpr = NULL;
OpExpr *greaterThanExpr = NULL;
lessThanExpr = MakeOpExpression(variable, BTLessEqualStrategyNumber);
greaterThanExpr = MakeOpExpression(variable, BTGreaterEqualStrategyNumber);
baseConstraint = make_and_qual((Node *) lessThanExpr, (Node *) greaterThanExpr);
return baseConstraint;
}
/*
* MakeOpExpression builds an operator expression node. This operator expression
* implements the operator clause as defined by the variable and the strategy
* number. The function is copied from CitusDB's shard pruning logic.
*/
static OpExpr *
MakeOpExpression(Var *variable, int16 strategyNumber)
{
Oid typeId = variable->vartype;
Oid typeModId = variable->vartypmod;
Oid collationId = variable->varcollid;
Oid accessMethodId = BTREE_AM_OID;
Oid operatorId = InvalidOid;
Const *constantValue = NULL;
OpExpr *expression = NULL;
/* Load the operator from system catalogs */
operatorId = GetOperatorByType(typeId, accessMethodId, strategyNumber);
constantValue = makeNullConst(typeId, typeModId, collationId);
/* Now make the expression with the given variable and a null constant */
expression = (OpExpr *) make_opclause(operatorId,
InvalidOid, /* no result type yet */
false, /* no return set */
(Expr *) variable,
(Expr *) constantValue,
InvalidOid, collationId);
/* Set implementing function id and result type */
expression->opfuncid = get_opcode(operatorId);
expression->opresulttype = get_func_rettype(expression->opfuncid);
return expression;
}
/*
* GetOperatorByType returns operator Oid for the given type, access method,
* and strategy number. Note that this function incorrectly errors out when
* the given type doesn't have its own operator but can use another compatible
* type's default operator. The function is copied from CitusDB's shard pruning
* logic.
*/
static Oid
GetOperatorByType(Oid typeId, Oid accessMethodId, int16 strategyNumber)
{
/* Get default operator class from pg_opclass */
Oid operatorClassId = GetDefaultOpClass(typeId, accessMethodId);
Oid operatorFamily = get_opclass_family(operatorClassId);
Oid operatorId = get_opfamily_member(operatorFamily, typeId, typeId, strategyNumber);
return operatorId;
}
/*
* UpdateConstraint updates the base constraint with the given min/max values.
* The function is copied from CitusDB's shard pruning logic.
*/
static void
UpdateConstraint(Node *baseConstraint, Datum minValue, Datum maxValue)
{
BoolExpr *andExpr = (BoolExpr *) baseConstraint;
Node *lessThanExpr = (Node *) linitial(andExpr->args);
Node *greaterThanExpr = (Node *) lsecond(andExpr->args);
Node *minNode = get_rightop((Expr *) greaterThanExpr);
Node *maxNode = get_rightop((Expr *) lessThanExpr);
Const *minConstant = NULL;
Const *maxConstant = NULL;
Assert(IsA(minNode, Const));
Assert(IsA(maxNode, Const));
minConstant = (Const *) minNode;
maxConstant = (Const *) maxNode;
minConstant->constvalue = minValue;
maxConstant->constvalue = maxValue;
minConstant->constisnull = false;
maxConstant->constisnull = false;
minConstant->constbyval = true;
maxConstant->constbyval = true;
}
/*
* SelectedBlockSkipList constructs a new StripeSkipList in which the
* non-selected blocks are removed from the given stripeSkipList.
*/
static StripeSkipList *
SelectedBlockSkipList(StripeSkipList *stripeSkipList, bool *projectedColumnMask,
bool *selectedBlockMask)
{
StripeSkipList *SelectedBlockSkipList = NULL;
ColumnBlockSkipNode **selectedBlockSkipNodeArray = NULL;
uint32 selectedBlockCount = 0;
uint32 blockIndex = 0;
uint32 columnIndex = 0;