Parallel executor support.

This code provides infrastructure for a parallel leader to start up
parallel workers to execute subtrees of the plan tree being executed
in the master.  User-supplied parameters from ParamListInfo are passed
down, but PARAM_EXEC parameters are not.  Various other constructs,
such as initplans, subplans, and CTEs, are also not currently shared.
Nevertheless, there's enough here to support a basic implementation of
parallel query, and we can lift some of the current restrictions as
needed.

Amit Kapila and Robert Haas

1 files changed, 155 insertions, 0 deletions

diff --git a/src/backend/nodes/params.c b/src/backend/nodes/params.c
index fb803f8ee8b..d093263589c 100644
--- a/src/backend/nodes/params.c
+++ b/src/backend/nodes/params.c
@@ -16,6 +16,7 @@
 #include "postgres.h"
 
 #include "nodes/params.h"
+#include "storage/shmem.h"
 #include "utils/datum.h"
 #include "utils/lsyscache.h"
 
@@ -73,3 +74,157 @@ copyParamList(ParamListInfo from)
 
 	return retval;
 }
+
+/*
+ * Estimate the amount of space required to serialize a ParamListInfo.
+ */
+Size
+EstimateParamListSpace(ParamListInfo paramLI)
+{
+	int		i;
+	Size	sz = sizeof(int);
+
+	if (paramLI == NULL || paramLI->numParams <= 0)
+		return sz;
+
+	for (i = 0; i < paramLI->numParams; i++)
+	{
+		ParamExternData *prm = &paramLI->params[i];
+		int16		typLen;
+		bool		typByVal;
+
+		/* give hook a chance in case parameter is dynamic */
+		if (!OidIsValid(prm->ptype) && paramLI->paramFetch != NULL)
+			(*paramLI->paramFetch) (paramLI, i + 1);
+
+		sz = add_size(sz, sizeof(Oid));			/* space for type OID */
+		sz = add_size(sz, sizeof(uint16));		/* space for pflags */
+
+		/* space for datum/isnull */
+		if (OidIsValid(prm->ptype))
+			get_typlenbyval(prm->ptype, &typLen, &typByVal);
+		else
+		{
+			/* If no type OID, assume by-value, like copyParamList does. */
+			typLen = sizeof(Datum);
+			typByVal = true;
+		}
+		sz = add_size(sz,
+			datumEstimateSpace(prm->value, prm->isnull, typByVal, typLen));
+	}
+
+	return sz;
+}
+
+/*
+ * Serialize a paramListInfo structure into caller-provided storage.
+ *
+ * We write the number of parameters first, as a 4-byte integer, and then
+ * write details for each parameter in turn.  The details for each parameter
+ * consist of a 4-byte type OID, 2 bytes of flags, and then the datum as
+ * serialized by datumSerialize().  The caller is responsible for ensuring
+ * that there is enough storage to store the number of bytes that will be
+ * written; use EstimateParamListSpace to find out how many will be needed.
+ * *start_address is updated to point to the byte immediately following those
+ * written.
+ *
+ * RestoreParamList can be used to recreate a ParamListInfo based on the
+ * serialized representation; this will be a static, self-contained copy
+ * just as copyParamList would create.
+ */
+void
+SerializeParamList(ParamListInfo paramLI, char **start_address)
+{
+	int			nparams;
+	int			i;
+
+	/* Write number of parameters. */
+	if (paramLI == NULL || paramLI->numParams <= 0)
+		nparams = 0;
+	else
+		nparams = paramLI->numParams;
+	memcpy(*start_address, &nparams, sizeof(int));
+	*start_address += sizeof(int);
+
+	/* Write each parameter in turn. */
+	for (i = 0; i < nparams; i++)
+	{
+		ParamExternData *prm = &paramLI->params[i];
+		int16		typLen;
+		bool		typByVal;
+
+		/* give hook a chance in case parameter is dynamic */
+		if (!OidIsValid(prm->ptype) && paramLI->paramFetch != NULL)
+			(*paramLI->paramFetch) (paramLI, i + 1);
+
+		/* Write type OID. */
+		memcpy(*start_address, &prm->ptype, sizeof(Oid));
+		*start_address += sizeof(Oid);
+
+		/* Write flags. */
+		memcpy(*start_address, &prm->pflags, sizeof(uint16));
+		*start_address += sizeof(uint16);
+
+		/* Write datum/isnull. */
+		if (OidIsValid(prm->ptype))
+			get_typlenbyval(prm->ptype, &typLen, &typByVal);
+		else
+		{
+			/* If no type OID, assume by-value, like copyParamList does. */
+			typLen = sizeof(Datum);
+			typByVal = true;
+		}
+		datumSerialize(prm->value, prm->isnull, typByVal, typLen,
+					   start_address);
+	}
+}
+
+/*
+ * Copy a ParamListInfo structure.
+ *
+ * The result is allocated in CurrentMemoryContext.
+ *
+ * Note: the intent of this function is to make a static, self-contained
+ * set of parameter values.  If dynamic parameter hooks are present, we
+ * intentionally do not copy them into the result.  Rather, we forcibly
+ * instantiate all available parameter values and copy the datum values.
+ */
+ParamListInfo
+RestoreParamList(char **start_address)
+{
+	ParamListInfo paramLI;
+	Size		size;
+	int			i;
+	int			nparams;
+
+	memcpy(&nparams, *start_address, sizeof(int));
+	*start_address += sizeof(int);
+
+	size = offsetof(ParamListInfoData, params) +
+		nparams * sizeof(ParamExternData);
+
+	paramLI = (ParamListInfo) palloc(size);
+	paramLI->paramFetch = NULL;
+	paramLI->paramFetchArg = NULL;
+	paramLI->parserSetup = NULL;
+	paramLI->parserSetupArg = NULL;
+	paramLI->numParams = nparams;
+
+	for (i = 0; i < nparams; i++)
+	{
+		ParamExternData *prm = &paramLI->params[i];
+
+		/* Read type OID. */
+		memcpy(&prm->ptype, *start_address, sizeof(Oid));
+		*start_address += sizeof(Oid);
+
+		/* Read flags. */
+		memcpy(&prm->pflags, *start_address, sizeof(uint16));
+		*start_address += sizeof(uint16);
+
+		/* Read datum/isnull. */
+		prm->value = datumRestore(start_address, &prm->isnull);
+	}
+
+	return paramLI;
+}