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citus/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.
*
* $Id$
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/nbtree.h"
#include "catalog/pg_am.h"
#include "commands/defrem.h"
#include "nodes/makefuncs.h"
#if PG_VERSION_NUM >= 120000
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#else
#include "optimizer/clauses.h"
#include "optimizer/predtest.h"
#endif
#include "optimizer/restrictinfo.h"
#include "storage/fd.h"
#include "utils/guc.h"
#include "utils/memutils.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "cstore.h"
#include "cstore_version_compat.h"
/* static function declarations */
static StripeBuffers * LoadFilteredStripeBuffers(Relation relation,
StripeMetadata *stripeMetadata,
TupleDesc tupleDescriptor,
List *projectedColumnList,
List *whereClauseList);
static void ReadStripeNextRow(StripeBuffers *stripeBuffers, List *projectedColumnList,
uint64 blockIndex, uint64 blockRowIndex,
BlockData *blockData, Datum *columnValues,
bool *columnNulls);
static ColumnBuffers * LoadColumnBuffers(Relation relation,
ColumnBlockSkipNode *blockSkipNodeArray,
uint32 blockCount, uint64 stripeOffset,
Form_pg_attribute attributeForm);
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 BlockData * DeserializeBlockData(StripeBuffers *stripeBuffers, uint64 blockIndex,
uint32 rowCount, TupleDesc tupleDescriptor,
List *projectedColumnList);
static Datum ColumnDefaultValue(TupleConstr *tupleConstraints,
Form_pg_attribute attributeForm);
static StringInfo ReadFromSmgr(Relation rel, uint64 offset, uint32 size);
/*
* 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(Relation relation, TupleDesc tupleDescriptor,
List *projectedColumnList, List *whereClauseList)
{
TableReadState *readState = NULL;
DataFileMetadata *datafileMetadata = NULL;
MemoryContext stripeReadContext = NULL;
Oid relNode = relation->rd_node.relNode;
datafileMetadata = ReadDataFileMetadata(relNode, false);
/*
* 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);
readState = palloc0(sizeof(TableReadState));
readState->relation = relation;
readState->datafileMetadata = datafileMetadata;
readState->projectedColumnList = projectedColumnList;
readState->whereClauseList = whereClauseList;
readState->stripeBuffers = NULL;
readState->readStripeCount = 0;
readState->stripeReadRowCount = 0;
readState->tupleDescriptor = tupleDescriptor;
readState->stripeReadContext = stripeReadContext;
readState->blockData = NULL;
readState->deserializedBlockIndex = -1;
return readState;
}
/*
* 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;
StripeMetadata *stripeMetadata = readState->currentStripeMetadata;
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;
List *stripeMetadataList = readState->datafileMetadata->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);
readState->blockData = NULL;
stripeMetadata = list_nth(stripeMetadataList, readState->readStripeCount);
stripeBuffers = LoadFilteredStripeBuffers(readState->relation,
stripeMetadata,
readState->tupleDescriptor,
readState->projectedColumnList,
readState->whereClauseList);
readState->readStripeCount++;
readState->currentStripeMetadata = stripeMetadata;
MemoryContextSwitchTo(oldContext);
if (stripeBuffers->rowCount != 0)
{
readState->stripeBuffers = stripeBuffers;
readState->stripeReadRowCount = 0;
readState->deserializedBlockIndex = -1;
break;
}
}
blockIndex = readState->stripeReadRowCount / stripeMetadata->blockRowCount;
blockRowIndex = readState->stripeReadRowCount % stripeMetadata->blockRowCount;
if (blockIndex != readState->deserializedBlockIndex)
{
uint32 lastBlockIndex = 0;
uint32 blockRowCount = 0;
uint32 stripeRowCount = 0;
stripeRowCount = stripeMetadata->rowCount;
lastBlockIndex = stripeRowCount / stripeMetadata->blockRowCount;
if (blockIndex == lastBlockIndex)
{
blockRowCount = stripeRowCount % stripeMetadata->blockRowCount;
}
else
{
blockRowCount = stripeMetadata->blockRowCount;
}
oldContext = MemoryContextSwitchTo(readState->stripeReadContext);
FreeBlockData(readState->blockData);
readState->blockData =
DeserializeBlockData(readState->stripeBuffers, blockIndex,
blockRowCount, readState->tupleDescriptor,
readState->projectedColumnList);
MemoryContextSwitchTo(oldContext);
readState->deserializedBlockIndex = blockIndex;
}
ReadStripeNextRow(readState->stripeBuffers, readState->projectedColumnList,
blockIndex, blockRowIndex, readState->blockData,
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;
}
/*
* CStoreRescan clears the position where we were scanning so that the next read starts at
* the beginning again
*/
void
CStoreRescan(TableReadState *readState)
{
readState->stripeBuffers = NULL;
readState->readStripeCount = 0;
readState->stripeReadRowCount = 0;
}
/* Finishes a cstore read operation. */
void
CStoreEndRead(TableReadState *readState)
{
MemoryContextDelete(readState->stripeReadContext);
list_free_deep(readState->datafileMetadata->stripeMetadataList);
pfree(readState->datafileMetadata);
pfree(readState);
}
/*
* CreateEmptyBlockDataArray creates data buffers to keep deserialized exist and
* value arrays for requested columns in columnMask.
*/
BlockData *
CreateEmptyBlockData(uint32 columnCount, bool *columnMask, uint32 blockRowCount)
{
uint32 columnIndex = 0;
BlockData *blockData = palloc0(sizeof(BlockData));
blockData->existsArray = palloc0(columnCount * sizeof(bool *));
blockData->valueArray = palloc0(columnCount * sizeof(Datum *));
blockData->valueBufferArray = palloc0(columnCount * sizeof(StringInfo));
blockData->columnCount = columnCount;
blockData->rowCount = blockRowCount;
/* allocate block memory for deserialized data */
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
if (columnMask[columnIndex])
{
blockData->existsArray[columnIndex] = palloc0(blockRowCount * sizeof(bool));
blockData->valueArray[columnIndex] = palloc0(blockRowCount * sizeof(Datum));
blockData->valueBufferArray[columnIndex] = NULL;
}
}
return blockData;
}
/*
* FreeBlockData 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
FreeBlockData(BlockData *blockData)
{
uint32 columnIndex = 0;
if (blockData == NULL)
{
return;
}
for (columnIndex = 0; columnIndex < blockData->columnCount; columnIndex++)
{
if (blockData->existsArray[columnIndex] != NULL)
{
pfree(blockData->existsArray[columnIndex]);
}
if (blockData->valueArray[columnIndex] != NULL)
{
pfree(blockData->valueArray[columnIndex]);
}
}
pfree(blockData->existsArray);
pfree(blockData->valueArray);
pfree(blockData);
}
/* CStoreTableRowCount returns the exact row count of a table using skiplists */
uint64
CStoreTableRowCount(Relation relation)
{
DataFileMetadata *datafileMetadata = NULL;
ListCell *stripeMetadataCell = NULL;
uint64 totalRowCount = 0;
datafileMetadata = ReadDataFileMetadata(relation->rd_node.relNode, false);
foreach(stripeMetadataCell, datafileMetadata->stripeMetadataList)
{
StripeMetadata *stripeMetadata = (StripeMetadata *) lfirst(stripeMetadataCell);
totalRowCount += stripeMetadata->rowCount;
}
return totalRowCount;
}
/*
* 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(Relation relation, StripeMetadata *stripeMetadata,
TupleDesc tupleDescriptor, List *projectedColumnList,
List *whereClauseList)
{
StripeBuffers *stripeBuffers = NULL;
ColumnBuffers **columnBuffersArray = NULL;
uint32 columnIndex = 0;
uint32 columnCount = tupleDescriptor->natts;
bool *projectedColumnMask = ProjectedColumnMask(columnCount, projectedColumnList);
StripeSkipList *stripeSkipList = ReadStripeSkipList(relation->rd_node.relNode,
stripeMetadata->id,
tupleDescriptor,
stripeMetadata->blockCount);
bool *selectedBlockMask = SelectedBlockMask(stripeSkipList, projectedColumnList,
whereClauseList);
StripeSkipList *selectedBlockSkipList =
SelectedBlockSkipList(stripeSkipList, projectedColumnMask,
selectedBlockMask);
/* load column data for projected columns */
columnBuffersArray = palloc0(columnCount * sizeof(ColumnBuffers *));
for (columnIndex = 0; columnIndex < stripeMetadata->columnCount; columnIndex++)
{
if (projectedColumnMask[columnIndex])
{
ColumnBlockSkipNode *blockSkipNode =
selectedBlockSkipList->blockSkipNodeArray[columnIndex];
Form_pg_attribute attributeForm = TupleDescAttr(tupleDescriptor, columnIndex);
uint32 blockCount = selectedBlockSkipList->blockCount;
ColumnBuffers *columnBuffers = LoadColumnBuffers(relation, blockSkipNode,
blockCount,
stripeMetadata->fileOffset,
attributeForm);
columnBuffersArray[columnIndex] = columnBuffers;
}
}
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,
BlockData *blockData, 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 columnIndex = projectedColumn->varattno - 1;
if (blockData->existsArray[columnIndex][blockRowIndex])
{
columnValues[columnIndex] = blockData->valueArray[columnIndex][blockRowIndex];
columnNulls[columnIndex] = 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(Relation relation, ColumnBlockSkipNode *blockSkipNodeArray,
uint32 blockCount, uint64 stripeOffset,
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 = stripeOffset + blockSkipNode->existsBlockOffset;
StringInfo rawExistsBuffer = ReadFromSmgr(relation, 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 = stripeOffset + blockSkipNode->valueBlockOffset;
StringInfo rawValueBuffer = ReadFromSmgr(relation, valueOffset,
blockSkipNode->valueLength);
blockBuffersArray[blockIndex]->valueBuffer = rawValueBuffer;
blockBuffersArray[blockIndex]->valueCompressionType = compressionType;
}
columnBuffers = palloc0(sizeof(ColumnBuffers));
columnBuffers->blockBuffersArray = blockBuffersArray;
return columnBuffers;
}
/*
* 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;
uint32 columnCount = stripeSkipList->columnCount;
for (blockIndex = 0; blockIndex < stripeSkipList->blockCount; blockIndex++)
{
if (selectedBlockMask[blockIndex])
{
selectedBlockCount++;
}
}
selectedBlockSkipNodeArray = palloc0(columnCount * sizeof(ColumnBlockSkipNode *));
for (columnIndex = 0; columnIndex < columnCount; columnIndex++)
{
uint32 selectedBlockIndex = 0;
bool firstColumn = columnIndex == 0;
/* first column's block skip node is always read */
if (!projectedColumnMask[columnIndex] && !firstColumn)
{
selectedBlockSkipNodeArray[columnIndex] = NULL;
continue;
}
Assert(stripeSkipList->blockSkipNodeArray[columnIndex] != NULL);
selectedBlockSkipNodeArray[columnIndex] = palloc0(selectedBlockCount *
sizeof(ColumnBlockSkipNode));
for (blockIndex = 0; blockIndex < stripeSkipList->blockCount; blockIndex++)
{
if (selectedBlockMask[blockIndex])
{
selectedBlockSkipNodeArray[columnIndex][selectedBlockIndex] =
stripeSkipList->blockSkipNodeArray[columnIndex][blockIndex];
selectedBlockIndex++;
}
}
}
SelectedBlockSkipList = palloc0(sizeof(StripeSkipList));
SelectedBlockSkipList->blockSkipNodeArray = selectedBlockSkipNodeArray;
SelectedBlockSkipList->blockCount = selectedBlockCount;
SelectedBlockSkipList->columnCount = stripeSkipList->columnCount;
return SelectedBlockSkipList;
}
/*
* StripeSkipListRowCount counts the number of rows in the given stripeSkipList.
* To do this, the function finds the first column, and sums up row counts across
* all blocks for that column.
*/
static uint32
StripeSkipListRowCount(StripeSkipList *stripeSkipList)
{
uint32 stripeSkipListRowCount = 0;
uint32 blockIndex = 0;
ColumnBlockSkipNode *firstColumnSkipNodeArray =
stripeSkipList->blockSkipNodeArray[0];
for (blockIndex = 0; blockIndex < stripeSkipList->blockCount; blockIndex++)
{
uint32 blockRowCount = firstColumnSkipNodeArray[blockIndex].rowCount;
stripeSkipListRowCount += blockRowCount;
}
return stripeSkipListRowCount;
}
/*
* ProjectedColumnMask returns a boolean array in which the projected columns
* from the projected column list are marked as true.
*/
static bool *
ProjectedColumnMask(uint32 columnCount, List *projectedColumnList)
{
bool *projectedColumnMask = palloc0(columnCount * sizeof(bool));
ListCell *columnCell = NULL;
foreach(columnCell, projectedColumnList)
{
Var *column = (Var *) lfirst(columnCell);
uint32 columnIndex = column->varattno - 1;
projectedColumnMask[columnIndex] = true;
}
return projectedColumnMask;
}
/*
* DeserializeBoolArray reads an array of bits from the given buffer and stores
* it in provided bool array.
*/
static void
DeserializeBoolArray(StringInfo boolArrayBuffer, bool *boolArray,
uint32 boolArrayLength)
{
uint32 boolArrayIndex = 0;
uint32 maximumBoolCount = boolArrayBuffer->len * 8;
if (boolArrayLength > maximumBoolCount)
{
ereport(ERROR, (errmsg("insufficient data for reading boolean array")));
}
for (boolArrayIndex = 0; boolArrayIndex < boolArrayLength; boolArrayIndex++)
{
uint32 byteIndex = boolArrayIndex / 8;
uint32 bitIndex = boolArrayIndex % 8;
uint8 bitmask = (1 << bitIndex);
uint8 shiftedBit = (boolArrayBuffer->data[byteIndex] & bitmask);
if (shiftedBit == 0)
{
boolArray[boolArrayIndex] = false;
}
else
{
boolArray[boolArrayIndex] = true;
}
}
}
/*
* DeserializeDatumArray reads an array of datums from the given buffer and stores
* them in provided datumArray. If a value is marked as false in the exists array,
* the function assumes that the datum isn't in the buffer, and simply skips it.
*/
static void
DeserializeDatumArray(StringInfo datumBuffer, bool *existsArray, uint32 datumCount,
bool datumTypeByValue, int datumTypeLength,
char datumTypeAlign, Datum *datumArray)
{
uint32 datumIndex = 0;
uint32 currentDatumDataOffset = 0;
for (datumIndex = 0; datumIndex < datumCount; datumIndex++)
{
char *currentDatumDataPointer = NULL;
if (!existsArray[datumIndex])
{
continue;
}
currentDatumDataPointer = datumBuffer->data + currentDatumDataOffset;
datumArray[datumIndex] = fetch_att(currentDatumDataPointer, datumTypeByValue,
datumTypeLength);
currentDatumDataOffset = att_addlength_datum(currentDatumDataOffset,
datumTypeLength,
currentDatumDataPointer);
currentDatumDataOffset = att_align_nominal(currentDatumDataOffset,
datumTypeAlign);
if (currentDatumDataOffset > datumBuffer->len)
{
ereport(ERROR, (errmsg("insufficient data left in datum buffer")));
}
}
}
/*
* DeserializeBlockData deserializes requested data block for all columns and
* stores in blockDataArray. It uncompresses serialized data if necessary. The
* function also deallocates data buffers used for previous block, and compressed
* data buffers for the current block which will not be needed again. If a column
* data is not present serialized buffer, then default value (or null) is used
* to fill value array.
*/
static BlockData *
DeserializeBlockData(StripeBuffers *stripeBuffers, uint64 blockIndex,
uint32 rowCount, TupleDesc tupleDescriptor,
List *projectedColumnList)
{
int columnIndex = 0;
bool *columnMask = ProjectedColumnMask(tupleDescriptor->natts, projectedColumnList);
BlockData *blockData = CreateEmptyBlockData(tupleDescriptor->natts, columnMask,
rowCount);
for (columnIndex = 0; columnIndex < stripeBuffers->columnCount; columnIndex++)
{
Form_pg_attribute attributeForm = TupleDescAttr(tupleDescriptor, columnIndex);
ColumnBuffers *columnBuffers = stripeBuffers->columnBuffersArray[columnIndex];
bool columnAdded = false;
if (columnBuffers == NULL && columnMask[columnIndex])
{
columnAdded = true;
}
if (columnBuffers != NULL)
{
ColumnBlockBuffers *blockBuffers =
columnBuffers->blockBuffersArray[blockIndex];
StringInfo valueBuffer = NULL;
/* decompress and deserialize current block's data */
valueBuffer = DecompressBuffer(blockBuffers->valueBuffer,
blockBuffers->valueCompressionType);
if (blockBuffers->valueCompressionType != COMPRESSION_NONE)
{
/* compressed data is not needed anymore */
pfree(blockBuffers->valueBuffer->data);
pfree(blockBuffers->valueBuffer);
}
DeserializeBoolArray(blockBuffers->existsBuffer,
blockData->existsArray[columnIndex],
rowCount);
DeserializeDatumArray(valueBuffer, blockData->existsArray[columnIndex],
rowCount, attributeForm->attbyval,
attributeForm->attlen, attributeForm->attalign,
blockData->valueArray[columnIndex]);
/* store current block's data buffer to be freed at next block read */
blockData->valueBufferArray[columnIndex] = valueBuffer;
}
else if (columnAdded)
{
/*
* This is a column that was added after creation of this stripe.
* So we use either the default value or NULL.
*/
if (attributeForm->atthasdef)
{
int rowIndex = 0;
Datum defaultValue = ColumnDefaultValue(tupleDescriptor->constr,
attributeForm);
for (rowIndex = 0; rowIndex < rowCount; rowIndex++)
{
blockData->existsArray[columnIndex][rowIndex] = true;
blockData->valueArray[columnIndex][rowIndex] = defaultValue;
}
}
else
{
memset(blockData->existsArray[columnIndex], false,
rowCount * sizeof(bool));
}
}
}
return blockData;
}
/*
* ColumnDefaultValue returns default value for given column. Only const values
* are supported. The function errors on any other default value expressions.
*/
static Datum
ColumnDefaultValue(TupleConstr *tupleConstraints, Form_pg_attribute attributeForm)
{
Node *defaultValueNode = NULL;
int defValIndex = 0;
for (defValIndex = 0; defValIndex < tupleConstraints->num_defval; defValIndex++)
{
AttrDefault attrDefault = tupleConstraints->defval[defValIndex];
if (attrDefault.adnum == attributeForm->attnum)
{
defaultValueNode = stringToNode(attrDefault.adbin);
break;
}
}
Assert(defaultValueNode != NULL);
/* try reducing the default value node to a const node */
defaultValueNode = eval_const_expressions(NULL, defaultValueNode);
if (IsA(defaultValueNode, Const))
{
Const *constNode = (Const *) defaultValueNode;
return constNode->constvalue;
}
else
{
const char *columnName = NameStr(attributeForm->attname);
ereport(ERROR, (errmsg("unsupported default value for column \"%s\"", columnName),
errhint("Expression is either mutable or "
"does not evaluate to constant value")));
}
}
static StringInfo
ReadFromSmgr(Relation rel, uint64 offset, uint32 size)
{
StringInfo resultBuffer = makeStringInfo();
uint64 read = 0;
enlargeStringInfo(resultBuffer, size);
resultBuffer->len = size;
while (read < size)
{
Buffer buffer;
Page page;
PageHeader phdr;
uint32 to_read;
SmgrAddr addr = logical_to_smgr(offset + read);
buffer = ReadBuffer(rel, addr.blockno);
page = BufferGetPage(buffer);
phdr = (PageHeader) page;
to_read = Min(size - read, phdr->pd_upper - addr.offset);
memcpy(resultBuffer->data + read, page + addr.offset, to_read);
ReleaseBuffer(buffer);
read += to_read;
}
return resultBuffer;
}
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